[Fix] throw an error for an invalid explicit main with a missing ./index.js file

Fixes #223. Fixes #143.

Author: pingrishabh

lib/async.js

@@ -267,7 +267,13 @@ module.exports = function resolve(x, options, callback) {
                             loadAsDirectory(dir, pkg, function (err, n, pkg) {
                                 if (err) return cb(err);
                                 if (n) return cb(null, n, pkg);
-                                loadAsFile(path.join(x, 'index'), pkg, cb);
+                                loadAsFile(path.join(x, 'index'), pkg, function (err, m, pkg) {
+                                    if (err) return cb(err);
+                                    if (m) return cb(null, m, pkg);
+                                    var incorrectMainError = new Error("Cannot find module '" + path.resolve(x, pkg.main) + "'. Please verify that the package.json has a valid \"main\" entry");
+                                    incorrectMainError.code = 'INCORRECT_PACKAGE_MAIN';
+                                    return cb(incorrectMainError);
+                                });
                             });
                         });
                         return;

lib/sync.js

@@ -168,11 +168,17 @@ module.exports = function resolveSync(x, options) {
                     pkg.main = 'index';
                 }
                 try {
-                    var m = loadAsFileSync(path.resolve(x, pkg.main));
+                    var mainPath = path.resolve(x, pkg.main);
+                    var m = loadAsFileSync(mainPath);
                     if (m) return m;
-                    var n = loadAsDirectorySync(path.resolve(x, pkg.main));
+                    var n = loadAsDirectorySync(mainPath);
                     if (n) return n;
-                } catch (e) {}
+                    var checkIndex = loadAsFileSync(path.resolve(x, 'index'));
+                    if (checkIndex) return checkIndex;
+                } catch (e) { }
+                var incorrectMainError = new Error("Cannot find module '" + path.resolve(x, pkg.main) + "'. Please verify that the package.json has a valid \"main\" entry");
+                incorrectMainError.code = 'INCORRECT_PACKAGE_MAIN';
+                throw incorrectMainError;
             }
         }
 

test/resolver.js

@@ -272,6 +272,18 @@ test('path iterator', function (t) {
     });
 });
 
+test('empty main', function (t) {
+    t.plan(1);
+
+    var resolverDir = path.join(__dirname, 'resolver');
+    var dir = path.join(resolverDir, 'empty_main');
+
+    resolve('./empty_main', { basedir: resolverDir }, function (err, res, pkg) {
+        if (err) t.fail(err);
+        t.equal(res, path.join(dir, 'index.js'));
+    });
+});
+
 test('incorrect main', function (t) {
     t.plan(1);
 
@@ -284,6 +296,40 @@ test('incorrect main', function (t) {
     });
 });
 
+test('missing index', function (t) {
+    t.plan(2);
+
+    var resolverDir = path.join(__dirname, 'resolver');
+    resolve('./missing_index', { basedir: resolverDir }, function (err, res, pkg) {
+        t.ok(err instanceof Error);
+        t.equal(err && err.code, 'INCORRECT_PACKAGE_MAIN', 'error has correct error code');
+    });
+});
+
+test('missing main', function (t) {
+    t.plan(1);
+
+    var resolverDir = path.join(__dirname, 'resolver');
+    var dir = path.join(resolverDir, 'missing_main');
+
+    resolve('./missing_main', { basedir: resolverDir }, function (err, res, pkg) {
+        if (err) t.fail(err);
+        t.equal(res, path.join(dir, 'index.js'));
+    });
+});
+
+test('null main', function (t) {
+    t.plan(1);
+
+    var resolverDir = path.join(__dirname, 'resolver');
+    var dir = path.join(resolverDir, 'null_main');
+
+    resolve('./null_main', { basedir: resolverDir }, function (err, res, pkg) {
+        if (err) t.fail(err);
+        t.equal(res, path.join(dir, 'index.js'));
+    });
+});
+
 test('without basedir', function (t) {
     t.plan(1);
 

test/resolver/empty_main/index.js

@@ -0,0 +1,3 @@
+{
+  "main": ""
+}

test/resolver/empty_main/package.json

@@ -0,0 +1,3 @@
+{
+  "main": "index.js"
+}

test/resolver/missing_index/package.json

@@ -0,0 +1,3 @@
+{
+  "notmain": "index.js"
+}

test/resolver/missing_main/index.js

@@ -0,0 +1,3 @@
+{
+  "main": null
+}