From db1e0a2d1fc42d42cfb2a5ace1b9c48259f2bf56 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Thu, 7 Mar 2019 02:03:37 -0800
Subject: [PATCH 01/13] esm: --type=auto, to detect module type based on
 whether source contains import or export

---
 lib/internal/main/check_syntax.js           |  4 ++-
 lib/internal/main/eval_stdin.js             |  7 ++++-
 lib/internal/main/eval_string.js            |  6 +++-
 lib/internal/modules/esm/default_resolve.js |  5 ++++
 lib/internal/modules/esm/detect_type.js     | 32 +++++++++++++++++++++
 node.gyp                                    |  1 +
 6 files changed, 52 insertions(+), 3 deletions(-)
 create mode 100644 lib/internal/modules/esm/detect_type.js

diff --git a/lib/internal/main/check_syntax.js b/lib/internal/main/check_syntax.js
index 6d335565ab..a7d0691675 100644
--- a/lib/internal/main/check_syntax.js
+++ b/lib/internal/main/check_syntax.js
@@ -60,7 +60,9 @@ function checkSyntax(source, filename) {
   if (experimentalModules) {
     let isModule = false;
     if (filename === '[stdin]' || filename === '[eval]') {
-      isModule = getOptionValue('--input-type') === 'module';
+      const typeFlag = getOptionValue('--input-type');
+      isModule = typeFlag === 'module' || (typeFlag === 'auto' &&
+        require('internal/modules/esm/detect_type')(source) === 'module');
     } else {
       const resolve = require('internal/modules/esm/default_resolve');
       const { format } = resolve(pathToFileURL(filename).toString());
diff --git a/lib/internal/main/eval_stdin.js b/lib/internal/main/eval_stdin.js
index 5c8f40b0e3..c3d8933fce 100644
--- a/lib/internal/main/eval_stdin.js
+++ b/lib/internal/main/eval_stdin.js
@@ -6,6 +6,8 @@ const {
   prepareMainThreadExecution
 } = require('internal/bootstrap/pre_execution');
 
+const { getOptionValue } = require('internal/options');
+
 const {
   evalModule,
   evalScript,
@@ -17,7 +19,10 @@ markBootstrapComplete();
 
 readStdin((code) => {
   process._eval = code;
-  if (require('internal/options').getOptionValue('--input-type') === 'module')
+  const typeFlag = getOptionValue('--input-type');
+  if (typeFlag === 'module' ||
+    (typeFlag === 'auto' &&
+     require('internal/modules/esm/detect_type')(code) === 'module'))
     evalModule(process._eval);
   else
     evalScript('[stdin]', process._eval, process._breakFirstLine);
diff --git a/lib/internal/main/eval_string.js b/lib/internal/main/eval_string.js
index 4597d2a0bb..0fe40ff65d 100644
--- a/lib/internal/main/eval_string.js
+++ b/lib/internal/main/eval_string.js
@@ -14,7 +14,11 @@ const source = getOptionValue('--eval');
 prepareMainThreadExecution();
 addBuiltinLibsToObject(global);
 markBootstrapComplete();
-if (getOptionValue('--input-type') === 'module')
+
+const typeFlag = getOptionValue('--input-type');
+if (typeFlag === 'module' ||
+  (typeFlag === 'auto' &&
+   require('internal/modules/esm/detect_type')(code) === 'module'))
   evalModule(source);
 else
   evalScript('[eval]', source, process._breakFirstLine);
diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index a83cf9c675..65c98566a6 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -94,6 +94,11 @@ function resolve(specifier, parentURL) {
     // entry point, etc.).
     throw new ERR_INPUT_TYPE_NOT_ALLOWED();
   }
+  // --entry-type=auto detects an ESM .js file within a CommonJS scope.
+  if (isMain && format === 'commonjs' && typeFlag === 'auto') {
+    const source = readFileSync(fileURLToPath(url), 'utf8');
+    format = require('internal/modules/esm/detect_type')(source);
+  }
   if (!format) {
     if (isMain)
       format = type === TYPE_MODULE ? 'module' : 'commonjs';
diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
new file mode 100644
index 0000000000..6c4785bab5
--- /dev/null
+++ b/lib/internal/modules/esm/detect_type.js
@@ -0,0 +1,32 @@
+'use strict';
+
+const acorn = require('internal/deps/acorn/acorn/dist/acorn');
+
+// Detect the module type of a file: CommonJS or ES module.
+// An ES module, for the purposes of this algorithm, is defined as any
+// JavaScript file containing an import or export statement.
+// Since our detection is so simple, we can avoid needing to use Acorn for a
+// full parse; we can detect import or export statements just from the tokens.
+function detectType(source) {
+  try {
+    let sawImport = false;
+    for (var token of acorn.tokenizer(source)) {
+      if (token.type.keyword === 'export')
+        return 'module';
+      if (token.type.keyword === 'import')
+        sawImport = true;
+      if (sawImport) {
+        // Skip `import(`; look only for import statements, not expressions.
+        if (token.type.label === '(')
+          sawImport = false;
+        else
+          return 'module';
+      }
+    }
+  } catch {
+    return 'commonjs';
+  }
+  return 'commonjs';
+}
+
+module.exports = detectType;
diff --git a/node.gyp b/node.gyp
index 676be6e038..b4d57af317 100644
--- a/node.gyp
+++ b/node.gyp
@@ -150,6 +150,7 @@
       'lib/internal/modules/esm/loader.js',
       'lib/internal/modules/esm/create_dynamic_module.js',
       'lib/internal/modules/esm/default_resolve.js',
+      'lib/internal/modules/esm/detect_type.js',
       'lib/internal/modules/esm/module_job.js',
       'lib/internal/modules/esm/module_map.js',
       'lib/internal/modules/esm/translators.js',

From 645f8f5bf4cc0607608fdec43c7663815c2e7bff Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Thu, 7 Mar 2019 22:33:42 -0800
Subject: [PATCH 02/13] esm: refactor import/export detection to use full
 parsing, as the tokens approach was too naive

---
 lib/internal/modules/esm/detect_type.js | 47 ++++++++++++++++---------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index 6c4785bab5..f9a40078cb 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -1,31 +1,46 @@
 'use strict';
 
 const acorn = require('internal/deps/acorn/acorn/dist/acorn');
+const walk = require('internal/deps/acorn/acorn-walk/dist/walk');
+
+class BreakWalk extends Error {}
 
 // Detect the module type of a file: CommonJS or ES module.
 // An ES module, for the purposes of this algorithm, is defined as any
 // JavaScript file containing an import or export statement.
-// Since our detection is so simple, we can avoid needing to use Acorn for a
-// full parse; we can detect import or export statements just from the tokens.
 function detectType(source) {
+  let ast;
   try {
-    let sawImport = false;
-    for (var token of acorn.tokenizer(source)) {
-      if (token.type.keyword === 'export')
-        return 'module';
-      if (token.type.keyword === 'import')
-        sawImport = true;
-      if (sawImport) {
-        // Skip `import(`; look only for import statements, not expressions.
-        if (token.type.label === '(')
-          sawImport = false;
-        else
-          return 'module';
-      }
-    }
+    ast = acorn.parse(source, {
+      ecmaVersion: 10, // Highest supported version as of 2019
+      allowReserved: true,
+      allowImportExportEverywhere: true,
+      allowAwaitOutsideFunction: true,
+      allowReturnOutsideFunction: true, // Required to parse CommonJS
+      allowHashBang: true // Required to parse hashbang scripts
+    });
   } catch {
     return 'commonjs';
   }
+
+  // Walk the AST until we encounter an import or export statement.
+  // We put this in try/catch so that we can stop walking as soon as we find
+  // either. Acorn-walk has no built-in break/early termination functionality,
+  // so try/catch provides it (https://github.com/acornjs/acorn/issues/685).
+  const walkedIntoImportOrExport = () => {
+    throw new BreakWalk();
+  };
+  try {
+    walk.simple(ast, {
+      ImportDeclaration: walkedIntoImportOrExport,
+      ExportNamedDeclaration: walkedIntoImportOrExport,
+      ExportDefaultDeclaration: walkedIntoImportOrExport,
+      ExportAllDeclaration: walkedIntoImportOrExport
+    });
+  } catch (err) {
+    if (err instanceof BreakWalk)
+      return 'module';
+  }
   return 'commonjs';
 }
 

From 7976ad3343045208e6ebe25adf1123b9c6fc5a16 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Fri, 8 Mar 2019 00:17:04 -0800
Subject: [PATCH 03/13] esm: tests for --type=auto

---
 test/es-module/test-esm-type-auto.js          | 37 +++++++++++++++++++
 .../ambiguous-with-import-expression.js       |  3 ++
 .../cjs-with-import-expression.js             |  5 +++
 .../cjs-with-property-named-import.js         |  3 ++
 .../type-auto-scope/cjs-with-require.js       |  3 ++
 .../cjs-with-string-containing-import.js      |  7 ++++
 .../esm-with-export-statement.js              |  6 +++
 .../esm-with-import-statement.js              |  2 +
 .../es-modules/type-auto-scope/package.json   |  1 +
 .../type-auto-scope/print-version.js          |  1 +
 10 files changed, 68 insertions(+)
 create mode 100644 test/es-module/test-esm-type-auto.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/cjs-with-require.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/package.json
 create mode 100644 test/fixtures/es-modules/type-auto-scope/print-version.js

diff --git a/test/es-module/test-esm-type-auto.js b/test/es-module/test-esm-type-auto.js
new file mode 100644
index 0000000000..0e96a8264a
--- /dev/null
+++ b/test/es-module/test-esm-type-auto.js
@@ -0,0 +1,37 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const exec = require('child_process').execFile;
+
+const version = process.version;
+
+expect('esm-with-import-statement.js', version);
+expect('esm-with-export-statement.js', version);
+
+expect('cjs-with-require.js', version);
+expect('cjs-with-import-expression.js', version);
+expect('cjs-with-property-named-import.js', version);
+expect('cjs-with-string-containing-import.js', version);
+
+expect('print-version.js', version);
+expect('ambiguous-with-import-expression.js', version);
+
+function expect(file, want) {
+  const argv = [
+    require.resolve(`../fixtures/es-modules/type-auto-scope/${file}`)
+  ];
+  ['--type=auto', '-a'].forEach((opt) => {
+    // TODO: Remove when --experimental-modules is unflagged
+    opt = `--experimental-modules ${opt}`;
+    const opts = {
+      env: Object.assign({}, process.env, { NODE_OPTIONS: opt }),
+      maxBuffer: 1e6,
+    };
+    exec(process.execPath, argv, opts,
+         common.mustCall((err, stdout, stderr) => {
+           if (stdout.includes(want)) return;
+           assert.fail(
+             `For ${file}, failed to find ${want} in: <\n${stdout}\n>`);
+         }));
+  });
+}
diff --git a/test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js b/test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js
new file mode 100644
index 0000000000..8513a2fe09
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js
@@ -0,0 +1,3 @@
+(async () => {
+  await import('./print-version.js');
+})();
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js
new file mode 100644
index 0000000000..4ca064ff0f
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js
@@ -0,0 +1,5 @@
+const { version } = require('process');
+
+(async () => {
+  await import('./print-version.js');
+})();
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
new file mode 100644
index 0000000000..e479ba3c2e
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
@@ -0,0 +1,3 @@
+global.import = 3;
+
+console.log(require('process').version);
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-require.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-require.js
new file mode 100644
index 0000000000..195ad7956a
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-require.js
@@ -0,0 +1,3 @@
+const { version } = require('process');
+
+console.log(version);
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js
new file mode 100644
index 0000000000..7f8319a90e
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js
@@ -0,0 +1,7 @@
+const { version } = require('process');
+
+const sneakyString = `
+import { version } from 'process';
+`;
+
+console.log(version);
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js b/test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js
new file mode 100644
index 0000000000..aed6f05d72
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js
@@ -0,0 +1,6 @@
+const version = process.version;
+
+export default version;
+
+console.log(version);
+
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js b/test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js
new file mode 100644
index 0000000000..fee4151c85
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js
@@ -0,0 +1,2 @@
+import { version } from 'process';
+console.log(version);
diff --git a/test/fixtures/es-modules/type-auto-scope/package.json b/test/fixtures/es-modules/type-auto-scope/package.json
new file mode 100644
index 0000000000..0967ef424b
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/package.json
@@ -0,0 +1 @@
+{}
diff --git a/test/fixtures/es-modules/type-auto-scope/print-version.js b/test/fixtures/es-modules/type-auto-scope/print-version.js
new file mode 100644
index 0000000000..557b2f103e
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/print-version.js
@@ -0,0 +1 @@
+console.log(process.version);

From 943417ced78451161adae53ebc32688272151ea3 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Fri, 8 Mar 2019 01:38:22 -0800
Subject: [PATCH 04/13] esm: acorn doesn't support import(), so revert to
 tokenizer approach; more tests

---
 lib/internal/modules/esm/detect_type.js       | 57 +++++++++----------
 test/es-module/test-esm-type-auto.js          |  3 +
 .../cjs-with-property-named-export.js         | 11 ++++
 .../cjs-with-property-named-import.js         | 11 ++++
 .../esm-with-import-expression.js             |  5 ++
 .../esm-with-indented-import-statement.js     |  2 +
 6 files changed, 58 insertions(+), 31 deletions(-)
 create mode 100644 test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js

diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index f9a40078cb..3a55633f77 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -1,46 +1,41 @@
 'use strict';
 
 const acorn = require('internal/deps/acorn/acorn/dist/acorn');
-const walk = require('internal/deps/acorn/acorn-walk/dist/walk');
-
-class BreakWalk extends Error {}
 
 // Detect the module type of a file: CommonJS or ES module.
 // An ES module, for the purposes of this algorithm, is defined as any
 // JavaScript file containing an import or export statement.
+// Since our detection is so simple, we can avoid needing to use Acorn for a
+// full parse; we can detect import or export statements just from the tokens.
+// Also as of this writing, Acorn doesn't support import() expressions as they
+// are only Stage 3; yet Node already supports them.
 function detectType(source) {
-  let ast;
   try {
-    ast = acorn.parse(source, {
-      ecmaVersion: 10, // Highest supported version as of 2019
-      allowReserved: true,
-      allowImportExportEverywhere: true,
-      allowAwaitOutsideFunction: true,
-      allowReturnOutsideFunction: true, // Required to parse CommonJS
-      allowHashBang: true // Required to parse hashbang scripts
-    });
+    let prevToken, prevPrevToken;
+    let sawKeyword = false;
+    for (const { type: token } of acorn.tokenizer(source)) {
+      if (token.keyword === 'import' || token.keyword === 'export') {
+        sawKeyword = true;
+      } else if (sawKeyword) {
+        // Skip `import(`; look only for import statements, not expressions.
+        // import() expressions are allowed in both CommonJS and ES modules.
+        if (token.label === '(' ||
+            // Also ensure that the keyword we just saw wasn't an allowed use
+            // of a reserved word as a property name; see
+            // test/fixtures/es-modules/type-auto-scope/
+            //   cjs-with-property-named-import.js
+            (prevPrevToken && prevPrevToken.label === '.') ||
+            token.label === ':')
+          sawKeyword = false;
+        else
+          return 'module';
+      }
+      prevPrevToken = prevToken;
+      prevToken = token;
+    }
   } catch {
     return 'commonjs';
   }
-
-  // Walk the AST until we encounter an import or export statement.
-  // We put this in try/catch so that we can stop walking as soon as we find
-  // either. Acorn-walk has no built-in break/early termination functionality,
-  // so try/catch provides it (https://github.com/acornjs/acorn/issues/685).
-  const walkedIntoImportOrExport = () => {
-    throw new BreakWalk();
-  };
-  try {
-    walk.simple(ast, {
-      ImportDeclaration: walkedIntoImportOrExport,
-      ExportNamedDeclaration: walkedIntoImportOrExport,
-      ExportDefaultDeclaration: walkedIntoImportOrExport,
-      ExportAllDeclaration: walkedIntoImportOrExport
-    });
-  } catch (err) {
-    if (err instanceof BreakWalk)
-      return 'module';
-  }
   return 'commonjs';
 }
 
diff --git a/test/es-module/test-esm-type-auto.js b/test/es-module/test-esm-type-auto.js
index 0e96a8264a..c3c690fdb9 100644
--- a/test/es-module/test-esm-type-auto.js
+++ b/test/es-module/test-esm-type-auto.js
@@ -7,10 +7,13 @@ const version = process.version;
 
 expect('esm-with-import-statement.js', version);
 expect('esm-with-export-statement.js', version);
+expect('esm-with-import-expression.js', version);
+expect('esm-with-indented-import-statement.js', version);
 
 expect('cjs-with-require.js', version);
 expect('cjs-with-import-expression.js', version);
 expect('cjs-with-property-named-import.js', version);
+expect('cjs-with-property-named-export.js', version);
 expect('cjs-with-string-containing-import.js', version);
 
 expect('print-version.js', version);
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js
new file mode 100644
index 0000000000..4389e477ad
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js
@@ -0,0 +1,11 @@
+// See ./cjs-with-property-named-import.js
+
+global.export = 3;
+
+global['export'] = 3;
+
+const obj = {
+export: 3 // Specifically at column 0, to try to trick the detector
+}
+
+console.log(require('process').version);
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
index e479ba3c2e..8dec066037 100644
--- a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
+++ b/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
@@ -1,3 +1,14 @@
+// In JavaScript, reserved words cannot be identifiers (the `foo` in `var foo`)
+// but they can be properties (`obj.foo`). This file checks that the `import`
+// reserved word isn't incorrectly detected as a keyword. For more info see:
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#Reserved_word_usage
+
 global.import = 3;
 
+global['import'] = 3;
+
+const obj = {
+import: 3 // Specifically at column 0, to try to trick the detector
+}
+
 console.log(require('process').version);
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js b/test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js
new file mode 100644
index 0000000000..83ed565b65
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js
@@ -0,0 +1,5 @@
+import { version } from 'process';
+
+(async () => {
+  await import('./print-version.js');
+})();
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js b/test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js
new file mode 100644
index 0000000000..ca9d4edc0f
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js
@@ -0,0 +1,2 @@
+  import { version } from 'process';
+  console.log(version);

From a833fdc744a40298a35e38032578153a6a5a153c Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Fri, 8 Mar 2019 12:52:45 -0800
Subject: [PATCH 05/13] esm: simplify logic in detect loop

---
 lib/internal/modules/esm/detect_type.js | 30 +++++++++++--------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index 3a55633f77..3d3d44ef95 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -12,24 +12,20 @@ const acorn = require('internal/deps/acorn/acorn/dist/acorn');
 function detectType(source) {
   try {
     let prevToken, prevPrevToken;
-    let sawKeyword = false;
     for (const { type: token } of acorn.tokenizer(source)) {
-      if (token.keyword === 'import' || token.keyword === 'export') {
-        sawKeyword = true;
-      } else if (sawKeyword) {
-        // Skip `import(`; look only for import statements, not expressions.
-        // import() expressions are allowed in both CommonJS and ES modules.
-        if (token.label === '(' ||
-            // Also ensure that the keyword we just saw wasn't an allowed use
-            // of a reserved word as a property name; see
-            // test/fixtures/es-modules/type-auto-scope/
-            //   cjs-with-property-named-import.js
-            (prevPrevToken && prevPrevToken.label === '.') ||
-            token.label === ':')
-          sawKeyword = false;
-        else
-          return 'module';
-      }
+      if (prevToken &&
+          // By definition import or export must be followed by another token.
+          (prevToken.keyword === 'import' || prevToken.keyword === 'export') &&
+          // Skip `import(`; look only for import statements, not expressions.
+          // import() expressions are allowed in both CommonJS and ES modules.
+          token.label !== '(' &&
+          // Also ensure that the keyword we just saw wasn't an allowed use
+          // of a reserved word as a property name; see
+          // test/fixtures/es-modules/type-auto-scope/
+          //   cjs-with-property-named-import.js
+          !(prevPrevToken && prevPrevToken.label === '.') &&
+          token.label !== ':')
+        return 'module';
       prevPrevToken = prevToken;
       prevToken = token;
     }

From 0db82f36b115051a827246e34b6b5abfe01faf5c Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Fri, 8 Mar 2019 23:04:05 -0800
Subject: [PATCH 06/13] esm: fixup: code style

---
 test/es-module/test-esm-type-auto.js        | 2 +-
 test/es-module/test-esm-type-flag-errors.js | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/es-module/test-esm-type-auto.js b/test/es-module/test-esm-type-auto.js
index c3c690fdb9..5aae08f6f7 100644
--- a/test/es-module/test-esm-type-auto.js
+++ b/test/es-module/test-esm-type-auto.js
@@ -27,7 +27,7 @@ function expect(file, want) {
     // TODO: Remove when --experimental-modules is unflagged
     opt = `--experimental-modules ${opt}`;
     const opts = {
-      env: Object.assign({}, process.env, { NODE_OPTIONS: opt }),
+      env: { ...process.env, NODE_OPTIONS: opt },
       maxBuffer: 1e6,
     };
     exec(process.execPath, argv, opts,
diff --git a/test/es-module/test-esm-type-flag-errors.js b/test/es-module/test-esm-type-flag-errors.js
index 169118e018..f4ad2e6f4a 100644
--- a/test/es-module/test-esm-type-flag-errors.js
+++ b/test/es-module/test-esm-type-flag-errors.js
@@ -28,7 +28,7 @@ function expect(opt = '', inputFile, want, wantsError = false) {
   opt = `--experimental-modules ${opt}`;
   const argv = [inputFile];
   const opts = {
-    env: Object.assign({}, process.env, { NODE_OPTIONS: opt }),
+    env: { ...process.env, NODE_OPTIONS: opt },
     maxBuffer: 1e6,
   };
   exec(process.execPath, argv, opts, common.mustCall((err, stdout, stderr) => {

From 2c5ed92c6e9c235c6d150ee2a16b9ecfa3e76e2f Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Sat, 9 Mar 2019 00:07:16 -0800
Subject: [PATCH 07/13] esm: --entry-type=auto should throw syntax errors
 directly

---
 lib/internal/main/check_syntax.js                    |  3 ++-
 lib/internal/main/eval_stdin.js                      |  2 +-
 lib/internal/main/eval_string.js                     |  2 +-
 lib/internal/modules/esm/default_resolve.js          |  5 +++--
 lib/internal/modules/esm/detect_type.js              | 12 ++++++++++--
 test/es-module/test-esm-type-auto.js                 | 10 +++++++++-
 .../es-modules/type-auto-scope/syntax-error-1.js     |  1 +
 .../es-modules/type-auto-scope/syntax-error-2.js     |  2 ++
 8 files changed, 29 insertions(+), 8 deletions(-)
 create mode 100644 test/fixtures/es-modules/type-auto-scope/syntax-error-1.js
 create mode 100644 test/fixtures/es-modules/type-auto-scope/syntax-error-2.js

diff --git a/lib/internal/main/check_syntax.js b/lib/internal/main/check_syntax.js
index a7d0691675..16c0b66e6a 100644
--- a/lib/internal/main/check_syntax.js
+++ b/lib/internal/main/check_syntax.js
@@ -62,7 +62,8 @@ function checkSyntax(source, filename) {
     if (filename === '[stdin]' || filename === '[eval]') {
       const typeFlag = getOptionValue('--input-type');
       isModule = typeFlag === 'module' || (typeFlag === 'auto' &&
-        require('internal/modules/esm/detect_type')(source) === 'module');
+        require('internal/modules/esm/detect_type')(source, filename) ===
+          'module');
     } else {
       const resolve = require('internal/modules/esm/default_resolve');
       const { format } = resolve(pathToFileURL(filename).toString());
diff --git a/lib/internal/main/eval_stdin.js b/lib/internal/main/eval_stdin.js
index c3d8933fce..0625b43bf2 100644
--- a/lib/internal/main/eval_stdin.js
+++ b/lib/internal/main/eval_stdin.js
@@ -22,7 +22,7 @@ readStdin((code) => {
   const typeFlag = getOptionValue('--input-type');
   if (typeFlag === 'module' ||
     (typeFlag === 'auto' &&
-     require('internal/modules/esm/detect_type')(code) === 'module'))
+    require('internal/modules/esm/detect_type')(code, '[stdin]') === 'module'))
     evalModule(process._eval);
   else
     evalScript('[stdin]', process._eval, process._breakFirstLine);
diff --git a/lib/internal/main/eval_string.js b/lib/internal/main/eval_string.js
index 0fe40ff65d..9903942fa4 100644
--- a/lib/internal/main/eval_string.js
+++ b/lib/internal/main/eval_string.js
@@ -18,7 +18,7 @@ markBootstrapComplete();
 const typeFlag = getOptionValue('--input-type');
 if (typeFlag === 'module' ||
   (typeFlag === 'auto' &&
-   require('internal/modules/esm/detect_type')(code) === 'module'))
+  require('internal/modules/esm/detect_type')(source, '[eval]') === 'module'))
   evalModule(source);
 else
   evalScript('[eval]', source, process._breakFirstLine);
diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 65c98566a6..0cc90704ec 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -96,8 +96,9 @@ function resolve(specifier, parentURL) {
   }
   // --entry-type=auto detects an ESM .js file within a CommonJS scope.
   if (isMain && format === 'commonjs' && typeFlag === 'auto') {
-    const source = readFileSync(fileURLToPath(url), 'utf8');
-    format = require('internal/modules/esm/detect_type')(source);
+    const filename = fileURLToPath(url);
+    const source = readFileSync(filename, 'utf8');
+    format = require('internal/modules/esm/detect_type')(source, filename);
   }
   if (!format) {
     if (isMain)
diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index 3d3d44ef95..bbb5f0a8a7 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -1,6 +1,9 @@
 'use strict';
 
 const acorn = require('internal/deps/acorn/acorn/dist/acorn');
+const {
+  stripShebang, stripBOM
+} = require('internal/modules/cjs/helpers');
 
 // Detect the module type of a file: CommonJS or ES module.
 // An ES module, for the purposes of this algorithm, is defined as any
@@ -9,7 +12,9 @@ const acorn = require('internal/deps/acorn/acorn/dist/acorn');
 // full parse; we can detect import or export statements just from the tokens.
 // Also as of this writing, Acorn doesn't support import() expressions as they
 // are only Stage 3; yet Node already supports them.
-function detectType(source) {
+function detectType(source, filename) {
+  source = stripShebang(source);
+  source = stripBOM(source);
   try {
     let prevToken, prevPrevToken;
     for (const { type: token } of acorn.tokenizer(source)) {
@@ -30,7 +35,10 @@ function detectType(source) {
       prevToken = token;
     }
   } catch {
-    return 'commonjs';
+    // If the tokenizer threw, there's a syntax error.
+    // Compile the script, this will throw with an informative error.
+    const vm = require('vm');
+    new vm.Script(source, { displayErrors: true, filename });
   }
   return 'commonjs';
 }
diff --git a/test/es-module/test-esm-type-auto.js b/test/es-module/test-esm-type-auto.js
index 5aae08f6f7..e59fbad86d 100644
--- a/test/es-module/test-esm-type-auto.js
+++ b/test/es-module/test-esm-type-auto.js
@@ -19,7 +19,10 @@ expect('cjs-with-string-containing-import.js', version);
 expect('print-version.js', version);
 expect('ambiguous-with-import-expression.js', version);
 
-function expect(file, want) {
+expect('syntax-error-1.js', 'SyntaxError', true);
+expect('syntax-error-2.js', 'SyntaxError', true);
+
+function expect(file, want, wantsError = false) {
   const argv = [
     require.resolve(`../fixtures/es-modules/type-auto-scope/${file}`)
   ];
@@ -32,6 +35,11 @@ function expect(file, want) {
     };
     exec(process.execPath, argv, opts,
          common.mustCall((err, stdout, stderr) => {
+           if (wantsError) {
+             stdout = stderr;
+           } else {
+             assert.ifError(err);
+           }
            if (stdout.includes(want)) return;
            assert.fail(
              `For ${file}, failed to find ${want} in: <\n${stdout}\n>`);
diff --git a/test/fixtures/es-modules/type-auto-scope/syntax-error-1.js b/test/fixtures/es-modules/type-auto-scope/syntax-error-1.js
new file mode 100644
index 0000000000..1f5d64097b
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/syntax-error-1.js
@@ -0,0 +1 @@
+export
\ No newline at end of file
diff --git a/test/fixtures/es-modules/type-auto-scope/syntax-error-2.js b/test/fixtures/es-modules/type-auto-scope/syntax-error-2.js
new file mode 100644
index 0000000000..11d0e77b48
--- /dev/null
+++ b/test/fixtures/es-modules/type-auto-scope/syntax-error-2.js
@@ -0,0 +1,2 @@
+const str = 'import
+var foo = 3;
\ No newline at end of file

From 92c963b055cdee22c9f80bc03f1a820bc131950f Mon Sep 17 00:00:00 2001
From: Jordan Harband <ljharb@gmail.com>
Date: Sat, 9 Mar 2019 00:20:41 -0800
Subject: [PATCH 08/13] esm: fixup: code style

Co-Authored-By: GeoffreyBooth <GeoffreyBooth@users.noreply.github.com>
---
 lib/internal/modules/esm/detect_type.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index bbb5f0a8a7..e1fb50a9fd 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -2,7 +2,8 @@
 
 const acorn = require('internal/deps/acorn/acorn/dist/acorn');
 const {
-  stripShebang, stripBOM
+  stripShebang,
+  stripBOM,
 } = require('internal/modules/cjs/helpers');
 
 // Detect the module type of a file: CommonJS or ES module.

From e537ade8cafe4744ea2918f001a0da8ddd6f0f83 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Tue, 2 Apr 2019 23:57:02 -0700
Subject: [PATCH 09/13] esm: fix tests

---
 lib/internal/modules/esm/default_resolve.js   |  2 +-
 lib/internal/modules/esm/detect_type.js       |  2 +-
 src/node_options.cc                           |  6 ++--
 ...pe-auto.js => test-esm-entry-type-auto.js} | 36 +++++++++----------
 .../ambiguous-with-import-expression.js       |  0
 .../cjs-with-import-expression.js             |  0
 .../cjs-with-property-named-export.js         |  0
 .../cjs-with-property-named-import.js         |  0
 .../cjs-with-require.js                       |  0
 .../cjs-with-string-containing-import.js      |  0
 .../esm-with-export-statement.js              |  0
 .../esm-with-import-expression.js             |  0
 .../esm-with-import-statement.js              |  0
 .../esm-with-indented-import-statement.js     |  0
 .../package.json                              |  0
 .../print-version.js                          |  0
 .../syntax-error-1.js                         |  0
 .../syntax-error-2.js                         |  0
 18 files changed, 23 insertions(+), 23 deletions(-)
 rename test/es-module/{test-esm-type-auto.js => test-esm-entry-type-auto.js} (60%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/ambiguous-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/cjs-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/cjs-with-property-named-export.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/cjs-with-property-named-import.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/cjs-with-require.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/cjs-with-string-containing-import.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/esm-with-export-statement.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/esm-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/esm-with-import-statement.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/esm-with-indented-import-statement.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/package.json (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/print-version.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/syntax-error-1.js (100%)
 rename test/fixtures/es-modules/{type-auto-scope => entry-type-auto-scope}/syntax-error-2.js (100%)

diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 0cc90704ec..6fd2e5b2d0 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -3,7 +3,7 @@
 const internalFS = require('internal/fs/utils');
 const { NativeModule } = require('internal/bootstrap/loaders');
 const { extname } = require('path');
-const { realpathSync } = require('fs');
+const { readFileSync, realpathSync } = require('fs');
 const { getOptionValue } = require('internal/options');
 
 const preserveSymlinks = getOptionValue('--preserve-symlinks');
diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index e1fb50a9fd..54d1955be7 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -27,7 +27,7 @@ function detectType(source, filename) {
           token.label !== '(' &&
           // Also ensure that the keyword we just saw wasn't an allowed use
           // of a reserved word as a property name; see
-          // test/fixtures/es-modules/type-auto-scope/
+          // test/fixtures/es-modules/entry-type-auto-scope/
           //   cjs-with-property-named-import.js
           !(prevPrevToken && prevPrevToken.label === '.') &&
           token.label !== ':')
diff --git a/src/node_options.cc b/src/node_options.cc
index 942280347e..010ede5841 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -112,8 +112,10 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors) {
       errors->push_back("--input-type requires "
                         "--experimental-modules to be enabled");
     }
-    if (module_type != "commonjs" && module_type != "module") {
-      errors->push_back("--input-type must be \"module\" or \"commonjs\"");
+    if (module_type != "commonjs" && module_type != "module" &&
+        module_type != "auto") {
+      errors->push_back("--input-type must be "
+                        "\"module\" or \"commonjs\" or \"auto\"");
     }
   }
 
diff --git a/test/es-module/test-esm-type-auto.js b/test/es-module/test-esm-entry-type-auto.js
similarity index 60%
rename from test/es-module/test-esm-type-auto.js
rename to test/es-module/test-esm-entry-type-auto.js
index e59fbad86d..92fb4f56fb 100644
--- a/test/es-module/test-esm-type-auto.js
+++ b/test/es-module/test-esm-entry-type-auto.js
@@ -24,25 +24,23 @@ expect('syntax-error-2.js', 'SyntaxError', true);
 
 function expect(file, want, wantsError = false) {
   const argv = [
-    require.resolve(`../fixtures/es-modules/type-auto-scope/${file}`)
+    require.resolve(`../fixtures/es-modules/entry-type-auto-scope/${file}`)
   ];
-  ['--type=auto', '-a'].forEach((opt) => {
+  const opts = {
     // TODO: Remove when --experimental-modules is unflagged
-    opt = `--experimental-modules ${opt}`;
-    const opts = {
-      env: { ...process.env, NODE_OPTIONS: opt },
-      maxBuffer: 1e6,
-    };
-    exec(process.execPath, argv, opts,
-         common.mustCall((err, stdout, stderr) => {
-           if (wantsError) {
-             stdout = stderr;
-           } else {
-             assert.ifError(err);
-           }
-           if (stdout.includes(want)) return;
-           assert.fail(
-             `For ${file}, failed to find ${want} in: <\n${stdout}\n>`);
-         }));
-  });
+    env: { ...process.env,
+           NODE_OPTIONS: '--experimental-modules --entry-type=auto' },
+    maxBuffer: 1e6,
+  };
+  exec(process.execPath, argv, opts,
+       common.mustCall((err, stdout, stderr) => {
+         if (wantsError) {
+           stdout = stderr;
+         } else {
+           assert.ifError(err);
+         }
+         if (stdout.includes(want)) return;
+         assert.fail(
+           `For ${file}, failed to find ${want} in: <\n${stdout}\n>`);
+       }));
 }
diff --git a/test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js b/test/fixtures/es-modules/entry-type-auto-scope/ambiguous-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/ambiguous-with-import-expression.js
rename to test/fixtures/es-modules/entry-type-auto-scope/ambiguous-with-import-expression.js
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js b/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/cjs-with-import-expression.js
rename to test/fixtures/es-modules/entry-type-auto-scope/cjs-with-import-expression.js
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js b/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-export.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-export.js
rename to test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-export.js
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js b/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-import.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/cjs-with-property-named-import.js
rename to test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-import.js
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-require.js b/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-require.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/cjs-with-require.js
rename to test/fixtures/es-modules/entry-type-auto-scope/cjs-with-require.js
diff --git a/test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js b/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-string-containing-import.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/cjs-with-string-containing-import.js
rename to test/fixtures/es-modules/entry-type-auto-scope/cjs-with-string-containing-import.js
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js b/test/fixtures/es-modules/entry-type-auto-scope/esm-with-export-statement.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/esm-with-export-statement.js
rename to test/fixtures/es-modules/entry-type-auto-scope/esm-with-export-statement.js
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js b/test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/esm-with-import-expression.js
rename to test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-expression.js
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js b/test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-statement.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/esm-with-import-statement.js
rename to test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-statement.js
diff --git a/test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js b/test/fixtures/es-modules/entry-type-auto-scope/esm-with-indented-import-statement.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/esm-with-indented-import-statement.js
rename to test/fixtures/es-modules/entry-type-auto-scope/esm-with-indented-import-statement.js
diff --git a/test/fixtures/es-modules/type-auto-scope/package.json b/test/fixtures/es-modules/entry-type-auto-scope/package.json
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/package.json
rename to test/fixtures/es-modules/entry-type-auto-scope/package.json
diff --git a/test/fixtures/es-modules/type-auto-scope/print-version.js b/test/fixtures/es-modules/entry-type-auto-scope/print-version.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/print-version.js
rename to test/fixtures/es-modules/entry-type-auto-scope/print-version.js
diff --git a/test/fixtures/es-modules/type-auto-scope/syntax-error-1.js b/test/fixtures/es-modules/entry-type-auto-scope/syntax-error-1.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/syntax-error-1.js
rename to test/fixtures/es-modules/entry-type-auto-scope/syntax-error-1.js
diff --git a/test/fixtures/es-modules/type-auto-scope/syntax-error-2.js b/test/fixtures/es-modules/entry-type-auto-scope/syntax-error-2.js
similarity index 100%
rename from test/fixtures/es-modules/type-auto-scope/syntax-error-2.js
rename to test/fixtures/es-modules/entry-type-auto-scope/syntax-error-2.js

From 6888e0b82e9f23167d59ab10c0491301c53bc35a Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Wed, 3 Apr 2019 20:01:47 -0700
Subject: [PATCH 10/13] esm: document auto in the ESM docs

---
 doc/api/esm.md                              | 7 +++++++
 lib/internal/modules/esm/default_resolve.js | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/doc/api/esm.md b/doc/api/esm.md
index 36dba24e29..16ac1c22dd 100644
--- a/doc/api/esm.md
+++ b/doc/api/esm.md
@@ -174,6 +174,13 @@ For completeness there is also `--input-type=commonjs`, for explicitly running
 string input as CommonJS. This is the default behavior if `--input-type` is
 unspecified.
 
+There is also `--input-type=auto`, which configures Node.js to interpret string
+input as an ES module if Node.js finds an `import` or `export` statement in the
+source code. (Note that dynamic `import()` expressions are different from
+`import` statements; `import()` is allowed in both CommonJS and ES modules.) If
+no `import` or `export` statements are found, the string is interpreted as
+CommonJS.
+
 ## Package Entry Points
 
 The `package.json` `"main"` field defines the entry point for a package,
diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 6fd2e5b2d0..87025d67c8 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -94,7 +94,7 @@ function resolve(specifier, parentURL) {
     // entry point, etc.).
     throw new ERR_INPUT_TYPE_NOT_ALLOWED();
   }
-  // --entry-type=auto detects an ESM .js file within a CommonJS scope.
+  // --input-type=auto detects an ESM .js file within a CommonJS scope.
   if (isMain && format === 'commonjs' && typeFlag === 'auto') {
     const filename = fileURLToPath(url);
     const source = readFileSync(filename, 'utf8');

From bbbf03d9c3d83689225c7b1514ce8bb063485a1a Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Wed, 3 Apr 2019 23:47:46 -0700
Subject: [PATCH 11/13] esm: rename tests for --input-type=auto

---
 lib/internal/modules/esm/detect_type.js                       | 2 +-
 ...est-esm-entry-type-auto.js => test-esm-input-type-auto.js} | 4 ++--
 .../ambiguous-with-import-expression.js                       | 0
 .../cjs-with-import-expression.js                             | 0
 .../cjs-with-property-named-export.js                         | 0
 .../cjs-with-property-named-import.js                         | 0
 .../cjs-with-require.js                                       | 0
 .../cjs-with-string-containing-import.js                      | 0
 .../esm-with-export-statement.js                              | 0
 .../esm-with-import-expression.js                             | 0
 .../esm-with-import-statement.js                              | 0
 .../esm-with-indented-import-statement.js                     | 0
 .../package.json                                              | 0
 .../print-version.js                                          | 0
 .../syntax-error-1.js                                         | 0
 .../syntax-error-2.js                                         | 0
 16 files changed, 3 insertions(+), 3 deletions(-)
 rename test/es-module/{test-esm-entry-type-auto.js => test-esm-input-type-auto.js} (91%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/ambiguous-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/cjs-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/cjs-with-property-named-export.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/cjs-with-property-named-import.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/cjs-with-require.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/cjs-with-string-containing-import.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/esm-with-export-statement.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/esm-with-import-expression.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/esm-with-import-statement.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/esm-with-indented-import-statement.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/package.json (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/print-version.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/syntax-error-1.js (100%)
 rename test/fixtures/es-modules/{entry-type-auto-scope => input-type-auto-scope}/syntax-error-2.js (100%)

diff --git a/lib/internal/modules/esm/detect_type.js b/lib/internal/modules/esm/detect_type.js
index 54d1955be7..4fac79aac5 100644
--- a/lib/internal/modules/esm/detect_type.js
+++ b/lib/internal/modules/esm/detect_type.js
@@ -27,7 +27,7 @@ function detectType(source, filename) {
           token.label !== '(' &&
           // Also ensure that the keyword we just saw wasn't an allowed use
           // of a reserved word as a property name; see
-          // test/fixtures/es-modules/entry-type-auto-scope/
+          // test/fixtures/es-modules/input-type-auto-scope/
           //   cjs-with-property-named-import.js
           !(prevPrevToken && prevPrevToken.label === '.') &&
           token.label !== ':')
diff --git a/test/es-module/test-esm-entry-type-auto.js b/test/es-module/test-esm-input-type-auto.js
similarity index 91%
rename from test/es-module/test-esm-entry-type-auto.js
rename to test/es-module/test-esm-input-type-auto.js
index 92fb4f56fb..f9eaaaf3f6 100644
--- a/test/es-module/test-esm-entry-type-auto.js
+++ b/test/es-module/test-esm-input-type-auto.js
@@ -24,12 +24,12 @@ expect('syntax-error-2.js', 'SyntaxError', true);
 
 function expect(file, want, wantsError = false) {
   const argv = [
-    require.resolve(`../fixtures/es-modules/entry-type-auto-scope/${file}`)
+    require.resolve(`../fixtures/es-modules/input-type-auto-scope/${file}`)
   ];
   const opts = {
     // TODO: Remove when --experimental-modules is unflagged
     env: { ...process.env,
-           NODE_OPTIONS: '--experimental-modules --entry-type=auto' },
+           NODE_OPTIONS: '--experimental-modules --input-type=auto' },
     maxBuffer: 1e6,
   };
   exec(process.execPath, argv, opts,
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/ambiguous-with-import-expression.js b/test/fixtures/es-modules/input-type-auto-scope/ambiguous-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/ambiguous-with-import-expression.js
rename to test/fixtures/es-modules/input-type-auto-scope/ambiguous-with-import-expression.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-import-expression.js b/test/fixtures/es-modules/input-type-auto-scope/cjs-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/cjs-with-import-expression.js
rename to test/fixtures/es-modules/input-type-auto-scope/cjs-with-import-expression.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-export.js b/test/fixtures/es-modules/input-type-auto-scope/cjs-with-property-named-export.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-export.js
rename to test/fixtures/es-modules/input-type-auto-scope/cjs-with-property-named-export.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-import.js b/test/fixtures/es-modules/input-type-auto-scope/cjs-with-property-named-import.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/cjs-with-property-named-import.js
rename to test/fixtures/es-modules/input-type-auto-scope/cjs-with-property-named-import.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-require.js b/test/fixtures/es-modules/input-type-auto-scope/cjs-with-require.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/cjs-with-require.js
rename to test/fixtures/es-modules/input-type-auto-scope/cjs-with-require.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/cjs-with-string-containing-import.js b/test/fixtures/es-modules/input-type-auto-scope/cjs-with-string-containing-import.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/cjs-with-string-containing-import.js
rename to test/fixtures/es-modules/input-type-auto-scope/cjs-with-string-containing-import.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/esm-with-export-statement.js b/test/fixtures/es-modules/input-type-auto-scope/esm-with-export-statement.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/esm-with-export-statement.js
rename to test/fixtures/es-modules/input-type-auto-scope/esm-with-export-statement.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-expression.js b/test/fixtures/es-modules/input-type-auto-scope/esm-with-import-expression.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-expression.js
rename to test/fixtures/es-modules/input-type-auto-scope/esm-with-import-expression.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-statement.js b/test/fixtures/es-modules/input-type-auto-scope/esm-with-import-statement.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/esm-with-import-statement.js
rename to test/fixtures/es-modules/input-type-auto-scope/esm-with-import-statement.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/esm-with-indented-import-statement.js b/test/fixtures/es-modules/input-type-auto-scope/esm-with-indented-import-statement.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/esm-with-indented-import-statement.js
rename to test/fixtures/es-modules/input-type-auto-scope/esm-with-indented-import-statement.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/package.json b/test/fixtures/es-modules/input-type-auto-scope/package.json
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/package.json
rename to test/fixtures/es-modules/input-type-auto-scope/package.json
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/print-version.js b/test/fixtures/es-modules/input-type-auto-scope/print-version.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/print-version.js
rename to test/fixtures/es-modules/input-type-auto-scope/print-version.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/syntax-error-1.js b/test/fixtures/es-modules/input-type-auto-scope/syntax-error-1.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/syntax-error-1.js
rename to test/fixtures/es-modules/input-type-auto-scope/syntax-error-1.js
diff --git a/test/fixtures/es-modules/entry-type-auto-scope/syntax-error-2.js b/test/fixtures/es-modules/input-type-auto-scope/syntax-error-2.js
similarity index 100%
rename from test/fixtures/es-modules/entry-type-auto-scope/syntax-error-2.js
rename to test/fixtures/es-modules/input-type-auto-scope/syntax-error-2.js

From aff36867b77145068f3422b61fa5841c0675b838 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Thu, 4 Apr 2019 00:05:45 -0700
Subject: [PATCH 12/13] esm: make --input-type=auto tests use string input

---
 test/es-module/test-esm-input-type-auto.js | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/test/es-module/test-esm-input-type-auto.js b/test/es-module/test-esm-input-type-auto.js
index f9eaaaf3f6..b6d5136793 100644
--- a/test/es-module/test-esm-input-type-auto.js
+++ b/test/es-module/test-esm-input-type-auto.js
@@ -2,29 +2,35 @@
 const common = require('../common');
 const assert = require('assert');
 const exec = require('child_process').execFile;
+const { readFileSync } = require('fs');
 
 const version = process.version;
 
 expect('esm-with-import-statement.js', version);
 expect('esm-with-export-statement.js', version);
-expect('esm-with-import-expression.js', version);
+// TODO: Enable import expression tests once import() is supported
+// in string input.
+// expect('esm-with-import-expression.js', version);
 expect('esm-with-indented-import-statement.js', version);
 
 expect('cjs-with-require.js', version);
-expect('cjs-with-import-expression.js', version);
+// expect('cjs-with-import-expression.js', version);
 expect('cjs-with-property-named-import.js', version);
 expect('cjs-with-property-named-export.js', version);
 expect('cjs-with-string-containing-import.js', version);
 
 expect('print-version.js', version);
-expect('ambiguous-with-import-expression.js', version);
+// expect('ambiguous-with-import-expression.js', version);
 
 expect('syntax-error-1.js', 'SyntaxError', true);
 expect('syntax-error-2.js', 'SyntaxError', true);
 
 function expect(file, want, wantsError = false) {
   const argv = [
-    require.resolve(`../fixtures/es-modules/input-type-auto-scope/${file}`)
+    '--eval',
+    readFileSync(
+      require.resolve(`../fixtures/es-modules/input-type-auto-scope/${file}`),
+      'utf8')
   ];
   const opts = {
     // TODO: Remove when --experimental-modules is unflagged

From c0eeba42bd5b34dcd57e396b56cd8dbb0c7ff168 Mon Sep 17 00:00:00 2001
From: Geoffrey Booth <webmaster@geoffreybooth.com>
Date: Thu, 4 Apr 2019 00:23:15 -0700
Subject: [PATCH 13/13] esm: fixup: --input-type doesn't apply to files

---
 lib/internal/modules/esm/default_resolve.js | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 87025d67c8..a83cf9c675 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -3,7 +3,7 @@
 const internalFS = require('internal/fs/utils');
 const { NativeModule } = require('internal/bootstrap/loaders');
 const { extname } = require('path');
-const { readFileSync, realpathSync } = require('fs');
+const { realpathSync } = require('fs');
 const { getOptionValue } = require('internal/options');
 
 const preserveSymlinks = getOptionValue('--preserve-symlinks');
@@ -94,12 +94,6 @@ function resolve(specifier, parentURL) {
     // entry point, etc.).
     throw new ERR_INPUT_TYPE_NOT_ALLOWED();
   }
-  // --input-type=auto detects an ESM .js file within a CommonJS scope.
-  if (isMain && format === 'commonjs' && typeFlag === 'auto') {
-    const filename = fileURLToPath(url);
-    const source = readFileSync(filename, 'utf8');
-    format = require('internal/modules/esm/detect_type')(source, filename);
-  }
   if (!format) {
     if (isMain)
       format = type === TYPE_MODULE ? 'module' : 'commonjs';