From 03377cb7bf2a1e8d6783d72fa929c5adbead8846 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Fri, 8 Apr 2016 14:44:43 -0700
Subject: [PATCH 1/8] Add suggestionList to return strings based on how simular
 they are to the input

---
 .../__tests__/suggestionList-test.js          | 28 +++++++
 src/utilities/suggestionList.js               | 78 +++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 src/utilities/__tests__/suggestionList-test.js
 create mode 100644 src/utilities/suggestionList.js

diff --git a/src/utilities/__tests__/suggestionList-test.js b/src/utilities/__tests__/suggestionList-test.js
new file mode 100644
index 0000000000..ee8d3ab083
--- /dev/null
+++ b/src/utilities/__tests__/suggestionList-test.js
@@ -0,0 +1,28 @@
+/**
+ *  Copyright (c) 2015, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+import { suggestionList } from '../suggestionList';
+
+describe('suggestionList', () => {
+
+  it('Returns results when input is empty', () => {
+    expect(suggestionList('', [ 'a' ])).to.deep.equal([ 'a' ]);
+  });
+
+  it('Returns empty array when there are no options', () => {
+    expect(suggestionList('input', [])).to.deep.equal([]);
+  });
+
+  it('Returns options sorted based on simularity', () => {
+    expect(suggestionList('abc', [ 'a', 'ab', 'abc' ]))
+      .to.deep.equal([ 'abc', 'ab', 'a' ]);
+  });
+});
diff --git a/src/utilities/suggestionList.js b/src/utilities/suggestionList.js
new file mode 100644
index 0000000000..3b08031fea
--- /dev/null
+++ b/src/utilities/suggestionList.js
@@ -0,0 +1,78 @@
+/* @flow */
+/**
+ *  Copyright (c) 2015, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+/**
+ * Given a JavaScript value and a GraphQL type, determine if the value will be
+ * accepted for that type. This is primarily useful for validating the
+ * runtime values of query variables.
+ */
+export function suggestionList(
+    input: string,
+    options: Array<string>
+  ): Array<string> {
+  let i;
+  const d = {};
+  const oLength = options.length;
+  for (i = 0; i < oLength; i++) {
+    d[options[i]] = lexicalDistance(input, options[i]);
+  }
+  const result = options.slice();
+  return result.sort((a , b) => d[a] - d[b]);
+}
+
+/**
+ * Computes the lexical distance between strings A and B.
+ *
+ * The "distance" between two strings is given by counting the minimum number
+ * of edits needed to transform string A into string B. An edit can be an
+ * insertion, deletion, or substitution of a single character, or a swap of two
+ * adjacent characters.
+ *
+ * This distance can be useful for detecting typos in input or sorting
+ *
+ * @param {string} a
+ * @param {string} b
+ * @return {int} distance in number of edits
+ */
+function lexicalDistance(a, b) {
+  let i;
+  let j;
+  const d = [];
+  const aLength = a.length;
+  const bLength = b.length;
+
+  for (i = 0; i <= aLength; i++) {
+    d[i] = [ i ];
+  }
+
+  for (j = 1; j <= bLength; j++) {
+    d[0][j] = j;
+  }
+
+  for (i = 1; i <= aLength; i++) {
+    for (j = 1; j <= bLength; j++) {
+      const cost = a[i - 1] === b[j - 1] ? 0 : 1;
+
+      d[i][j] = Math.min(
+        d[i - 1][j] + 1,
+        d[i][j - 1] + 1,
+        d[i - 1][j - 1] + cost
+      );
+
+      if (i > 1 && j > 1 &&
+          a[i - 1] === b[j - 2] &&
+          a[i - 2] === b[j - 1]) {
+        d[i][j] = Math.min(d[i][j], d[i - 2][j - 2] + cost);
+      }
+    }
+  }
+
+  return d[aLength][bLength];
+}

From c4e619f669664973ff55a86bc698f2004b26e224 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Fri, 8 Apr 2016 14:46:59 -0700
Subject: [PATCH 2/8] Suggests valid fields in `FieldsOnCorrectType`

---
 .../__tests__/FieldsOnCorrectType-test.js     | 146 +++++++++++++++---
 src/validation/rules/FieldsOnCorrectType.js   |  42 ++++-
 2 files changed, 162 insertions(+), 26 deletions(-)

diff --git a/src/validation/__tests__/FieldsOnCorrectType-test.js b/src/validation/__tests__/FieldsOnCorrectType-test.js
index 496eece221..b1f7c0ca37 100644
--- a/src/validation/__tests__/FieldsOnCorrectType-test.js
+++ b/src/validation/__tests__/FieldsOnCorrectType-test.js
@@ -16,9 +16,21 @@ import {
 } from '../rules/FieldsOnCorrectType';
 
 
-function undefinedField(field, type, suggestions, line, column) {
+function undefinedField(
+  field,
+  type,
+  suggestedTypes,
+  suggestedFields,
+  line,
+  column
+) {
   return {
-    message: undefinedFieldMessage(field, type, suggestions),
+    message: undefinedFieldMessage(
+      field,
+      type,
+      suggestedTypes,
+      suggestedFields
+    ),
     locations: [ { line, column } ],
   };
 }
@@ -85,8 +97,16 @@ describe('Validate: Fields on correct type', () => {
           }
         }
       }`,
-      [ undefinedField('unknown_pet_field', 'Pet', [], 3, 9),
-        undefinedField('unknown_cat_field', 'Cat', [], 5, 13) ]
+      [ undefinedField('unknown_pet_field', 'Pet', [], [ 'name' ], 3, 9),
+        undefinedField(
+          'unknown_cat_field',
+          'Cat',
+          [],
+          [ 'nickname', 'name', 'meowVolume', 'meows', 'furColor' ],
+          5,
+          13
+        )
+      ]
     );
   });
 
@@ -95,7 +115,22 @@ describe('Validate: Fields on correct type', () => {
       fragment fieldNotDefined on Dog {
         meowVolume
       }`,
-      [ undefinedField('meowVolume', 'Dog', [], 3, 9) ]
+      [ undefinedField(
+          'meowVolume',
+          'Dog',
+          [],
+          [ 'barkVolume',
+            'name',
+            'nickname',
+            'barks',
+            'doesKnowCommand',
+            'isAtLocation',
+            'isHousetrained',
+          ],
+          3,
+          9
+        )
+      ]
     );
   });
 
@@ -106,7 +141,22 @@ describe('Validate: Fields on correct type', () => {
           deeper_unknown_field
         }
       }`,
-      [ undefinedField('unknown_field', 'Dog', [], 3, 9) ]
+      [ undefinedField(
+          'unknown_field',
+          'Dog',
+          [],
+          [ 'nickname',
+            'name',
+            'barkVolume',
+            'doesKnowCommand',
+            'isHousetrained',
+            'isAtLocation',
+            'barks',
+          ],
+          3,
+          9
+        )
+      ]
     );
   });
 
@@ -117,7 +167,7 @@ describe('Validate: Fields on correct type', () => {
           unknown_field
         }
       }`,
-      [ undefinedField('unknown_field', 'Pet', [], 4, 11) ]
+      [ undefinedField('unknown_field', 'Pet', [], [ 'name' ], 4, 11) ]
     );
   });
 
@@ -128,7 +178,22 @@ describe('Validate: Fields on correct type', () => {
           meowVolume
         }
       }`,
-      [ undefinedField('meowVolume', 'Dog', [], 4, 11) ]
+      [ undefinedField(
+          'meowVolume',
+          'Dog',
+          [],
+          [ 'barkVolume',
+            'name',
+            'nickname',
+            'barks',
+            'doesKnowCommand',
+            'isAtLocation',
+            'isHousetrained',
+          ],
+          4,
+          11
+        )
+      ]
     );
   });
 
@@ -137,7 +202,22 @@ describe('Validate: Fields on correct type', () => {
       fragment aliasedFieldTargetNotDefined on Dog {
         volume : mooVolume
       }`,
-      [ undefinedField('mooVolume', 'Dog', [], 3, 9) ]
+      [ undefinedField(
+          'mooVolume',
+          'Dog',
+          [],
+          [ 'barkVolume',
+            'name',
+            'nickname',
+            'barks',
+            'isAtLocation',
+            'doesKnowCommand',
+            'isHousetrained',
+          ],
+          3,
+          9
+        )
+      ]
     );
   });
 
@@ -146,7 +226,22 @@ describe('Validate: Fields on correct type', () => {
       fragment aliasedLyingFieldTargetNotDefined on Dog {
         barkVolume : kawVolume
       }`,
-      [ undefinedField('kawVolume', 'Dog', [], 3, 9) ]
+      [ undefinedField(
+          'kawVolume',
+          'Dog',
+          [],
+          [ 'barkVolume',
+            'name',
+            'nickname',
+            'barks',
+            'isAtLocation',
+            'doesKnowCommand',
+            'isHousetrained',
+          ],
+          3,
+          9
+        )
+      ]
     );
   });
 
@@ -155,7 +250,7 @@ describe('Validate: Fields on correct type', () => {
       fragment notDefinedOnInterface on Pet {
         tailLength
       }`,
-      [ undefinedField('tailLength', 'Pet', [], 3, 9) ]
+      [ undefinedField('tailLength', 'Pet', [], [ 'name' ], 3, 9) ]
     );
   });
 
@@ -164,7 +259,7 @@ describe('Validate: Fields on correct type', () => {
       fragment definedOnImplementorsButNotInterface on Pet {
         nickname
       }`,
-      [ undefinedField('nickname', 'Pet', [ 'Cat', 'Dog' ], 3, 9) ]
+      [ undefinedField('nickname', 'Pet', [ 'Cat', 'Dog' ], [ 'name' ], 3, 9) ]
     );
   });
 
@@ -181,7 +276,7 @@ describe('Validate: Fields on correct type', () => {
       fragment directFieldSelectionOnUnion on CatOrDog {
         directField
       }`,
-      [ undefinedField('directField', 'CatOrDog', [], 3, 9) ]
+      [ undefinedField('directField', 'CatOrDog', [], [], 3, 9) ]
     );
   });
 
@@ -195,6 +290,7 @@ describe('Validate: Fields on correct type', () => {
           'name',
           'CatOrDog',
           [ 'Being', 'Pet', 'Canine', 'Cat', 'Dog' ],
+          [],
           3,
           9
         )
@@ -218,25 +314,33 @@ describe('Validate: Fields on correct type', () => {
   describe('Fields on correct type error message', () => {
     it('Works with no suggestions', () => {
       expect(
-        undefinedFieldMessage('T', 'f', [])
-      ).to.equal('Cannot query field "T" on type "f".');
+        undefinedFieldMessage('f', 'T', [], [])
+      ).to.equal('Cannot query field "f" on type "T".');
     });
 
     it('Works with no small numbers of suggestions', () => {
       expect(
-        undefinedFieldMessage('T', 'f', [ 'A', 'B' ])
-      ).to.equal('Cannot query field "T" on type "f". ' +
+        undefinedFieldMessage('f', 'T', [ 'A', 'B' ], [ 'z', 'y' ])
+      ).to.equal('Cannot query field "f" on type "T". ' +
         'However, this field exists on "A", "B". ' +
-        'Perhaps you meant to use an inline fragment?');
+        'Perhaps you meant to use an inline fragment? ' +
+        'Did you mean to query "z", "y"?');
     });
 
     it('Works with lots of suggestions', () => {
       expect(
-        undefinedFieldMessage('T', 'f', [ 'A', 'B', 'C', 'D', 'E', 'F' ])
-      ).to.equal('Cannot query field "T" on type "f". ' +
+        undefinedFieldMessage(
+          'f',
+          'T',
+          [ 'A', 'B', 'C', 'D', 'E', 'F' ],
+          [ 'z', 'y', 'x', 'w', 'v', 'u' ]
+        )
+      ).to.equal('Cannot query field "f" on type "T". ' +
         'However, this field exists on "A", "B", "C", "D", "E", ' +
         'and 1 other types. ' +
-        'Perhaps you meant to use an inline fragment?');
+        'Perhaps you meant to use an inline fragment? ' +
+        'Did you mean to query "z", "y", "x", "w", "v", or 1 other field?'
+      );
     });
   });
 });
diff --git a/src/validation/rules/FieldsOnCorrectType.js b/src/validation/rules/FieldsOnCorrectType.js
index f2962afa68..275d24980d 100644
--- a/src/validation/rules/FieldsOnCorrectType.js
+++ b/src/validation/rules/FieldsOnCorrectType.js
@@ -13,13 +13,20 @@ import { GraphQLError } from '../../error';
 import type { Field } from '../../language/ast';
 import type { GraphQLSchema } from '../../type/schema';
 import type { GraphQLAbstractType } from '../../type/definition';
-import { isAbstractType } from '../../type/definition';
+import {
+  isAbstractType,
+  GraphQLObjectType,
+  GraphQLInputObjectType,
+  GraphQLInterfaceType
+} from '../../type/definition';
+import { suggestionList } from '../../utilities/suggestionList';
 
 
 export function undefinedFieldMessage(
   fieldName: string,
   type: string,
-  suggestedTypes: Array<string>
+  suggestedTypes: Array<string>,
+  suggestedFields: Array<string>
 ): string {
   let message = `Cannot query field "${fieldName}" on type "${type}".`;
   const MAX_LENGTH = 5;
@@ -34,6 +41,18 @@ export function undefinedFieldMessage(
     message += ` However, this field exists on ${suggestions}.`;
     message += ' Perhaps you meant to use an inline fragment?';
   }
+  if (suggestedFields.length !== 0) {
+    let suggestions = suggestedFields
+      .slice(0, MAX_LENGTH)
+      .map(t => `"${t}"`)
+      .join(', ');
+    if (suggestedFields.length > MAX_LENGTH) {
+      suggestions += `, or ${suggestedFields.length - MAX_LENGTH} other field`;
+    }
+    message +=
+      ` Did you mean to query ${suggestions}?`;
+
+  }
   return message;
 }
 
@@ -50,10 +69,10 @@ export function FieldsOnCorrectType(context: ValidationContext): any {
       if (type) {
         const fieldDef = context.getFieldDef();
         if (!fieldDef) {
+          const schema = context.getSchema();
           // This isn't valid. Let's find suggestions, if any.
           let suggestedTypes = [];
           if (isAbstractType(type)) {
-            const schema = context.getSchema();
             suggestedTypes = getSiblingInterfacesIncludingField(
               schema,
               type,
@@ -63,8 +82,22 @@ export function FieldsOnCorrectType(context: ValidationContext): any {
               getImplementationsIncludingField(schema, type, node.name.value)
             );
           }
+          let suggestedFields = [];
+          if (type instanceof GraphQLObjectType ||
+              type instanceof GraphQLInterfaceType ||
+              type instanceof GraphQLInputObjectType) {
+            suggestedFields = suggestionList(
+              node.name.value,
+              Object.keys(schema.getType(type.name).getFields())
+            );
+          }
           context.reportError(new GraphQLError(
-            undefinedFieldMessage(node.name.value, type.name, suggestedTypes),
+            undefinedFieldMessage(
+              node.name.value,
+              type.name,
+              suggestedTypes,
+              suggestedFields
+            ),
             [ node ]
           ));
         }
@@ -113,4 +146,3 @@ function getSiblingInterfacesIncludingField(
   return Object.keys(suggestedInterfaces)
     .sort((a,b) => suggestedInterfaces[b] - suggestedInterfaces[a]);
 }
-

From e25fe3e1b1524e464775e44cad149afe1614e617 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Tue, 12 Apr 2016 12:05:24 -0400
Subject: [PATCH 3/8] Suggest argument names

---
 .../__tests__/KnownArgumentNames-test.js      | 26 ++++++-----
 src/validation/rules/KnownArgumentNames.js    | 45 ++++++++++++++++---
 2 files changed, 54 insertions(+), 17 deletions(-)

diff --git a/src/validation/__tests__/KnownArgumentNames-test.js b/src/validation/__tests__/KnownArgumentNames-test.js
index bc9fec1ec9..56df9580ef 100644
--- a/src/validation/__tests__/KnownArgumentNames-test.js
+++ b/src/validation/__tests__/KnownArgumentNames-test.js
@@ -16,16 +16,22 @@ import {
 } from '../rules/KnownArgumentNames';
 
 
-function unknownArg(argName, fieldName, typeName, line, column) {
+function unknownArg(argName, fieldName, typeName, suggestedArgs, line, column) {
   return {
-    message: unknownArgMessage(argName, fieldName, typeName),
+    message: unknownArgMessage(argName, fieldName, typeName, suggestedArgs),
     locations: [ { line, column } ],
   };
 }
 
-function unknownDirectiveArg(argName, directiveName, line, column) {
+function unknownDirectiveArg(
+  argName,
+  directiveName,
+  suggestedArgs,
+  line,
+  column
+) {
   return {
-    message: unknownDirectiveArgMessage(argName, directiveName),
+    message: unknownDirectiveArgMessage(argName, directiveName, suggestedArgs),
     locations: [ { line, column } ],
   };
 }
@@ -103,7 +109,7 @@ describe('Validate: Known argument names', () => {
         dog @skip(unless: true)
       }
     `, [
-      unknownDirectiveArg('unless', 'skip', 3, 19),
+      unknownDirectiveArg('unless', 'skip', [], 3, 19),
     ]);
   });
 
@@ -113,7 +119,7 @@ describe('Validate: Known argument names', () => {
         doesKnowCommand(unknown: true)
       }
     `, [
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', 3, 25),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 25),
     ]);
   });
 
@@ -123,8 +129,8 @@ describe('Validate: Known argument names', () => {
         doesKnowCommand(whoknows: 1, dogCommand: SIT, unknown: true)
       }
     `, [
-      unknownArg('whoknows', 'doesKnowCommand', 'Dog', 3, 25),
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', 3, 55),
+      unknownArg('whoknows', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 25),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 55),
     ]);
   });
 
@@ -143,8 +149,8 @@ describe('Validate: Known argument names', () => {
         }
       }
     `, [
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', 4, 27),
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', 9, 31),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 4, 27),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 9, 31),
     ]);
   });
 
diff --git a/src/validation/rules/KnownArgumentNames.js b/src/validation/rules/KnownArgumentNames.js
index e389d65371..4594c54d44 100644
--- a/src/validation/rules/KnownArgumentNames.js
+++ b/src/validation/rules/KnownArgumentNames.js
@@ -17,22 +17,42 @@ import {
   DIRECTIVE
 } from '../../language/kinds';
 import type { GraphQLType } from '../../type/definition';
-
+import { suggestionList } from '../../utilities/suggestionList';
 
 export function unknownArgMessage(
   argName: string,
   fieldName: string,
-  type: GraphQLType
+  type: GraphQLType,
+  suggestedArgs: Array<string>
 ): string {
-  return `Unknown argument "${argName}" on field "${fieldName}" of ` +
+  let message = `Unknown argument "${argName}" on field "${fieldName}" of ` +
     `type "${type}".`;
+  if (suggestedArgs.length) {
+    const suggestions = suggestedArgs
+      .map(t => `"${t}"`)
+      .join(', ');
+    message += ` Perhaps you meant ${suggestions}?`;
+  } else {
+    message += ' There is no known argument for this field.';
+  }
+  return message;
 }
 
 export function unknownDirectiveArgMessage(
   argName: string,
-  directiveName: string
+  directiveName: string,
+  suggestedArgs: Array<string>
 ): string {
-  return `Unknown argument "${argName}" on directive "@${directiveName}".`;
+  let message =
+    `Unknown argument "${argName}" on directive "@${directiveName}".`;
+  if (suggestedArgs.length) {
+    const suggestions = suggestedArgs
+      .map(t => `"${t}"`)
+      .join(', ');
+    message += ` Perhaps you meant ${suggestions}?`;
+  } else {
+    message += ' There is no known argument for this directive.';
+  }
 }
 
 /**
@@ -59,7 +79,11 @@ export function KnownArgumentNames(context: ValidationContext): any {
               unknownArgMessage(
                 node.name.value,
                 fieldDef.name,
-                parentType.name
+                parentType.name,
+                suggestionList(
+                  node.name.value,
+                  fieldDef.args.map(arg => arg.name)
+                )
               ),
               [ node ]
             ));
@@ -74,7 +98,14 @@ export function KnownArgumentNames(context: ValidationContext): any {
           );
           if (!directiveArgDef) {
             context.reportError(new GraphQLError(
-              unknownDirectiveArgMessage(node.name.value, directive.name),
+              unknownDirectiveArgMessage(
+                node.name.value,
+                directive.name,
+                suggestionList(
+                  node.name.value,
+                  directive.args.map(arg => arg.name)
+                )
+              ),
               [ node ]
             ));
           }

From d460b744c39e03a6e59b1d3b0d08468a31aea7c7 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Tue, 12 Apr 2016 13:21:11 -0400
Subject: [PATCH 4/8] Suggested valid type names

---
 .../__tests__/KnownTypeNames-test.js          | 52 ++++++++++++++++---
 src/validation/rules/KnownTypeNames.js        | 29 +++++++++--
 2 files changed, 70 insertions(+), 11 deletions(-)

diff --git a/src/validation/__tests__/KnownTypeNames-test.js b/src/validation/__tests__/KnownTypeNames-test.js
index e158ad3acb..a7e7b91f35 100644
--- a/src/validation/__tests__/KnownTypeNames-test.js
+++ b/src/validation/__tests__/KnownTypeNames-test.js
@@ -15,9 +15,9 @@ import {
 } from '../rules/KnownTypeNames';
 
 
-function unknownType(typeName, line, column) {
+function unknownType(typeName, suggestedTypes, line, column) {
   return {
-    message: unknownTypeMessage(typeName),
+    message: unknownTypeMessage(typeName, suggestedTypes),
     locations: [ { line, column } ],
   };
 }
@@ -49,9 +49,39 @@ describe('Validate: Known type names', () => {
         name
       }
     `, [
-      unknownType('JumbledUpLetters', 2, 23),
-      unknownType('Badger', 5, 25),
-      unknownType('Peettt', 8, 29)
+      unknownType(
+        'JumbledUpLetters',
+        [ 'ComplexInput',
+          'ComplicatedArgs',
+          'QueryRoot',
+          'Intelligent',
+          'HumanOrAlien'
+        ],
+        2,
+        23
+      ),
+      unknownType(
+        'Badger',
+        [ 'Dog',
+          'Boolean',
+          'Pet',
+          'Alien',
+          'Being'
+        ],
+        5,
+        25
+      ),
+      unknownType(
+        'Peettt',
+        [ 'Pet',
+          'Float',
+          'Being',
+          'Cat',
+          'Int'
+        ],
+        8,
+        29
+      )
     ]);
   });
 
@@ -73,7 +103,17 @@ describe('Validate: Known type names', () => {
         }
       }
     `, [
-      unknownType('NotInTheSchema', 12, 23),
+      unknownType(
+        'NotInTheSchema',
+        [ '__Schema',
+          'Intelligent',
+          'HumanOrAlien',
+          'Int',
+          'Canine'
+        ],
+        12,
+        23
+      ),
     ]);
   });
 
diff --git a/src/validation/rules/KnownTypeNames.js b/src/validation/rules/KnownTypeNames.js
index 6ab367c3d9..701c318f22 100644
--- a/src/validation/rules/KnownTypeNames.js
+++ b/src/validation/rules/KnownTypeNames.js
@@ -11,10 +11,22 @@
 import type { ValidationContext } from '../index';
 import { GraphQLError } from '../../error';
 import type { GraphQLType } from '../../type/definition';
+import { suggestionList } from '../../utilities/suggestionList';
 
-
-export function unknownTypeMessage(type: GraphQLType): string {
-  return `Unknown type "${type}".`;
+export function unknownTypeMessage(
+  type: GraphQLType,
+  suggestedTypes: Arrray<string>
+): string {
+  let message = `Unknown type "${type}".`;
+  const MAX_LENGTH = 5;
+  if (suggestedTypes.length) {
+    const suggestions = suggestedTypes
+      .slice(0, MAX_LENGTH)
+      .map(t => `"${t}"`)
+      .join(', ');
+    message += ` Perhaps you meant one of the following: ${suggestions}.`;
+  }
+  return message;
 }
 
 /**
@@ -33,11 +45,18 @@ export function KnownTypeNames(context: ValidationContext): any {
     UnionTypeDefinition: () => false,
     InputObjectTypeDefinition: () => false,
     NamedType(node) {
+      const schema = context.getSchema();
       const typeName = node.name.value;
-      const type = context.getSchema().getType(typeName);
+      const type = schema.getType(typeName);
       if (!type) {
         context.reportError(
-          new GraphQLError(unknownTypeMessage(typeName), [ node ])
+          new GraphQLError(
+            unknownTypeMessage(
+              typeName,
+              suggestionList(typeName, Object.keys(schema.getTypeMap()))
+            ),
+            [ node ]
+          )
         );
       }
     }

From 10997c5c7d3929afe77cc01ba05ca67414601823 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Tue, 12 Apr 2016 13:30:42 -0400
Subject: [PATCH 5/8] Fix flow and unit test

---
 src/validation/__tests__/KnownArgumentNames-test.js | 2 +-
 src/validation/rules/KnownArgumentNames.js          | 1 +
 src/validation/rules/KnownTypeNames.js              | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/validation/__tests__/KnownArgumentNames-test.js b/src/validation/__tests__/KnownArgumentNames-test.js
index 56df9580ef..922e79868b 100644
--- a/src/validation/__tests__/KnownArgumentNames-test.js
+++ b/src/validation/__tests__/KnownArgumentNames-test.js
@@ -109,7 +109,7 @@ describe('Validate: Known argument names', () => {
         dog @skip(unless: true)
       }
     `, [
-      unknownDirectiveArg('unless', 'skip', [], 3, 19),
+      unknownDirectiveArg('unless', 'skip', [ 'if' ], 3, 19),
     ]);
   });
 
diff --git a/src/validation/rules/KnownArgumentNames.js b/src/validation/rules/KnownArgumentNames.js
index 4594c54d44..d8578aff0b 100644
--- a/src/validation/rules/KnownArgumentNames.js
+++ b/src/validation/rules/KnownArgumentNames.js
@@ -53,6 +53,7 @@ export function unknownDirectiveArgMessage(
   } else {
     message += ' There is no known argument for this directive.';
   }
+  return message;
 }
 
 /**
diff --git a/src/validation/rules/KnownTypeNames.js b/src/validation/rules/KnownTypeNames.js
index 701c318f22..dd7420b3b1 100644
--- a/src/validation/rules/KnownTypeNames.js
+++ b/src/validation/rules/KnownTypeNames.js
@@ -15,7 +15,7 @@ import { suggestionList } from '../../utilities/suggestionList';
 
 export function unknownTypeMessage(
   type: GraphQLType,
-  suggestedTypes: Arrray<string>
+  suggestedTypes: Array<string>
 ): string {
   let message = `Unknown type "${type}".`;
   const MAX_LENGTH = 5;

From 8982f88f3a411e29d8e7a159946df94021bae49d Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Tue, 12 Apr 2016 21:51:16 -0400
Subject: [PATCH 6/8] addressed comments in PR: move file, update comment,
 filter out more options, remove redundant warning

---
 .../__tests__/suggestionList-test.js          |  2 +-
 src/{utilities => jsutils}/suggestionList.js  | 14 +++--
 .../__tests__/FieldsOnCorrectType-test.js     | 53 ++++---------------
 .../__tests__/KnownArgumentNames-test.js      | 12 ++---
 .../__tests__/KnownTypeNames-test.js          | 28 ++--------
 src/validation/rules/FieldsOnCorrectType.js   |  4 +-
 src/validation/rules/KnownArgumentNames.js    |  7 +--
 src/validation/rules/KnownTypeNames.js        |  3 +-
 8 files changed, 35 insertions(+), 88 deletions(-)
 rename src/{utilities => jsutils}/__tests__/suggestionList-test.js (95%)
 rename src/{utilities => jsutils}/suggestionList.js (80%)

diff --git a/src/utilities/__tests__/suggestionList-test.js b/src/jsutils/__tests__/suggestionList-test.js
similarity index 95%
rename from src/utilities/__tests__/suggestionList-test.js
rename to src/jsutils/__tests__/suggestionList-test.js
index ee8d3ab083..585431458c 100644
--- a/src/utilities/__tests__/suggestionList-test.js
+++ b/src/jsutils/__tests__/suggestionList-test.js
@@ -23,6 +23,6 @@ describe('suggestionList', () => {
 
   it('Returns options sorted based on simularity', () => {
     expect(suggestionList('abc', [ 'a', 'ab', 'abc' ]))
-      .to.deep.equal([ 'abc', 'ab', 'a' ]);
+      .to.deep.equal([ 'abc', 'ab' ]);
   });
 });
diff --git a/src/utilities/suggestionList.js b/src/jsutils/suggestionList.js
similarity index 80%
rename from src/utilities/suggestionList.js
rename to src/jsutils/suggestionList.js
index 3b08031fea..cc524c17a5 100644
--- a/src/utilities/suggestionList.js
+++ b/src/jsutils/suggestionList.js
@@ -9,9 +9,8 @@
  */
 
 /**
- * Given a JavaScript value and a GraphQL type, determine if the value will be
- * accepted for that type. This is primarily useful for validating the
- * runtime values of query variables.
+ * Given an invalid input string and a list of valid options, returns a filtered
+ * list of valid options sorted based on their simularity with the input.
  */
 export function suggestionList(
     input: string,
@@ -20,10 +19,15 @@ export function suggestionList(
   let i;
   const d = {};
   const oLength = options.length;
+  const inputThreshold = input.length / 2;
   for (i = 0; i < oLength; i++) {
-    d[options[i]] = lexicalDistance(input, options[i]);
+    const distance = lexicalDistance(input, options[i]);
+    const threshold = Math.max(inputThreshold, options[i].length / 2, 1);
+    if (distance <= threshold) {
+      d[options[i]] = distance;
+    }
   }
-  const result = options.slice();
+  const result = Object.keys(d);
   return result.sort((a , b) => d[a] - d[b]);
 }
 
diff --git a/src/validation/__tests__/FieldsOnCorrectType-test.js b/src/validation/__tests__/FieldsOnCorrectType-test.js
index b1f7c0ca37..b74133cd13 100644
--- a/src/validation/__tests__/FieldsOnCorrectType-test.js
+++ b/src/validation/__tests__/FieldsOnCorrectType-test.js
@@ -97,12 +97,12 @@ describe('Validate: Fields on correct type', () => {
           }
         }
       }`,
-      [ undefinedField('unknown_pet_field', 'Pet', [], [ 'name' ], 3, 9),
+      [ undefinedField('unknown_pet_field', 'Pet', [], [], 3, 9),
         undefinedField(
           'unknown_cat_field',
           'Cat',
           [],
-          [ 'nickname', 'name', 'meowVolume', 'meows', 'furColor' ],
+          [],
           5,
           13
         )
@@ -119,14 +119,7 @@ describe('Validate: Fields on correct type', () => {
           'meowVolume',
           'Dog',
           [],
-          [ 'barkVolume',
-            'name',
-            'nickname',
-            'barks',
-            'doesKnowCommand',
-            'isAtLocation',
-            'isHousetrained',
-          ],
+          [ 'barkVolume' ],
           3,
           9
         )
@@ -145,14 +138,7 @@ describe('Validate: Fields on correct type', () => {
           'unknown_field',
           'Dog',
           [],
-          [ 'nickname',
-            'name',
-            'barkVolume',
-            'doesKnowCommand',
-            'isHousetrained',
-            'isAtLocation',
-            'barks',
-          ],
+          [],
           3,
           9
         )
@@ -167,7 +153,7 @@ describe('Validate: Fields on correct type', () => {
           unknown_field
         }
       }`,
-      [ undefinedField('unknown_field', 'Pet', [], [ 'name' ], 4, 11) ]
+      [ undefinedField('unknown_field', 'Pet', [], [], 4, 11) ]
     );
   });
 
@@ -182,14 +168,7 @@ describe('Validate: Fields on correct type', () => {
           'meowVolume',
           'Dog',
           [],
-          [ 'barkVolume',
-            'name',
-            'nickname',
-            'barks',
-            'doesKnowCommand',
-            'isAtLocation',
-            'isHousetrained',
-          ],
+          [ 'barkVolume' ],
           4,
           11
         )
@@ -206,14 +185,7 @@ describe('Validate: Fields on correct type', () => {
           'mooVolume',
           'Dog',
           [],
-          [ 'barkVolume',
-            'name',
-            'nickname',
-            'barks',
-            'isAtLocation',
-            'doesKnowCommand',
-            'isHousetrained',
-          ],
+          [ 'barkVolume' ],
           3,
           9
         )
@@ -230,14 +202,7 @@ describe('Validate: Fields on correct type', () => {
           'kawVolume',
           'Dog',
           [],
-          [ 'barkVolume',
-            'name',
-            'nickname',
-            'barks',
-            'isAtLocation',
-            'doesKnowCommand',
-            'isHousetrained',
-          ],
+          [ 'barkVolume' ],
           3,
           9
         )
@@ -250,7 +215,7 @@ describe('Validate: Fields on correct type', () => {
       fragment notDefinedOnInterface on Pet {
         tailLength
       }`,
-      [ undefinedField('tailLength', 'Pet', [], [ 'name' ], 3, 9) ]
+      [ undefinedField('tailLength', 'Pet', [], [], 3, 9) ]
     );
   });
 
diff --git a/src/validation/__tests__/KnownArgumentNames-test.js b/src/validation/__tests__/KnownArgumentNames-test.js
index 922e79868b..eeae9cef1f 100644
--- a/src/validation/__tests__/KnownArgumentNames-test.js
+++ b/src/validation/__tests__/KnownArgumentNames-test.js
@@ -109,7 +109,7 @@ describe('Validate: Known argument names', () => {
         dog @skip(unless: true)
       }
     `, [
-      unknownDirectiveArg('unless', 'skip', [ 'if' ], 3, 19),
+      unknownDirectiveArg('unless', 'skip', [], 3, 19),
     ]);
   });
 
@@ -119,7 +119,7 @@ describe('Validate: Known argument names', () => {
         doesKnowCommand(unknown: true)
       }
     `, [
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 25),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [], 3, 25),
     ]);
   });
 
@@ -129,8 +129,8 @@ describe('Validate: Known argument names', () => {
         doesKnowCommand(whoknows: 1, dogCommand: SIT, unknown: true)
       }
     `, [
-      unknownArg('whoknows', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 25),
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 3, 55),
+      unknownArg('whoknows', 'doesKnowCommand', 'Dog', [], 3, 25),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [], 3, 55),
     ]);
   });
 
@@ -149,8 +149,8 @@ describe('Validate: Known argument names', () => {
         }
       }
     `, [
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 4, 27),
-      unknownArg('unknown', 'doesKnowCommand', 'Dog', [ 'dogCommand' ], 9, 31),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [], 4, 27),
+      unknownArg('unknown', 'doesKnowCommand', 'Dog', [], 9, 31),
     ]);
   });
 
diff --git a/src/validation/__tests__/KnownTypeNames-test.js b/src/validation/__tests__/KnownTypeNames-test.js
index a7e7b91f35..eca4a0424c 100644
--- a/src/validation/__tests__/KnownTypeNames-test.js
+++ b/src/validation/__tests__/KnownTypeNames-test.js
@@ -51,34 +51,19 @@ describe('Validate: Known type names', () => {
     `, [
       unknownType(
         'JumbledUpLetters',
-        [ 'ComplexInput',
-          'ComplicatedArgs',
-          'QueryRoot',
-          'Intelligent',
-          'HumanOrAlien'
-        ],
+        [],
         2,
         23
       ),
       unknownType(
         'Badger',
-        [ 'Dog',
-          'Boolean',
-          'Pet',
-          'Alien',
-          'Being'
-        ],
+        [],
         5,
         25
       ),
       unknownType(
         'Peettt',
-        [ 'Pet',
-          'Float',
-          'Being',
-          'Cat',
-          'Int'
-        ],
+        [ 'Pet' ],
         8,
         29
       )
@@ -105,12 +90,7 @@ describe('Validate: Known type names', () => {
     `, [
       unknownType(
         'NotInTheSchema',
-        [ '__Schema',
-          'Intelligent',
-          'HumanOrAlien',
-          'Int',
-          'Canine'
-        ],
+        [],
         12,
         23
       ),
diff --git a/src/validation/rules/FieldsOnCorrectType.js b/src/validation/rules/FieldsOnCorrectType.js
index 275d24980d..9738ec33f2 100644
--- a/src/validation/rules/FieldsOnCorrectType.js
+++ b/src/validation/rules/FieldsOnCorrectType.js
@@ -10,6 +10,7 @@
 
 import type { ValidationContext } from '../index';
 import { GraphQLError } from '../../error';
+import { suggestionList } from '../../jsutils/suggestionList';
 import type { Field } from '../../language/ast';
 import type { GraphQLSchema } from '../../type/schema';
 import type { GraphQLAbstractType } from '../../type/definition';
@@ -19,7 +20,6 @@ import {
   GraphQLInputObjectType,
   GraphQLInterfaceType
 } from '../../type/definition';
-import { suggestionList } from '../../utilities/suggestionList';
 
 
 export function undefinedFieldMessage(
@@ -88,7 +88,7 @@ export function FieldsOnCorrectType(context: ValidationContext): any {
               type instanceof GraphQLInputObjectType) {
             suggestedFields = suggestionList(
               node.name.value,
-              Object.keys(schema.getType(type.name).getFields())
+              Object.keys(type.getFields())
             );
           }
           context.reportError(new GraphQLError(
diff --git a/src/validation/rules/KnownArgumentNames.js b/src/validation/rules/KnownArgumentNames.js
index d8578aff0b..9f9c3dc11c 100644
--- a/src/validation/rules/KnownArgumentNames.js
+++ b/src/validation/rules/KnownArgumentNames.js
@@ -12,12 +12,13 @@ import type { ValidationContext } from '../index';
 import { GraphQLError } from '../../error';
 import find from '../../jsutils/find';
 import invariant from '../../jsutils/invariant';
+import { suggestionList } from '../../jsutils/suggestionList';
 import {
   FIELD,
   DIRECTIVE
 } from '../../language/kinds';
 import type { GraphQLType } from '../../type/definition';
-import { suggestionList } from '../../utilities/suggestionList';
+
 
 export function unknownArgMessage(
   argName: string,
@@ -32,8 +33,6 @@ export function unknownArgMessage(
       .map(t => `"${t}"`)
       .join(', ');
     message += ` Perhaps you meant ${suggestions}?`;
-  } else {
-    message += ' There is no known argument for this field.';
   }
   return message;
 }
@@ -50,8 +49,6 @@ export function unknownDirectiveArgMessage(
       .map(t => `"${t}"`)
       .join(', ');
     message += ` Perhaps you meant ${suggestions}?`;
-  } else {
-    message += ' There is no known argument for this directive.';
   }
   return message;
 }
diff --git a/src/validation/rules/KnownTypeNames.js b/src/validation/rules/KnownTypeNames.js
index dd7420b3b1..c8858ba15f 100644
--- a/src/validation/rules/KnownTypeNames.js
+++ b/src/validation/rules/KnownTypeNames.js
@@ -10,8 +10,9 @@
 
 import type { ValidationContext } from '../index';
 import { GraphQLError } from '../../error';
+import { suggestionList } from '../../jsutils/suggestionList';
 import type { GraphQLType } from '../../type/definition';
-import { suggestionList } from '../../utilities/suggestionList';
+
 
 export function unknownTypeMessage(
   type: GraphQLType,

From 6a80c4339fb5bf36aefd6ee78d3e47af215ff963 Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Mon, 18 Apr 2016 10:29:51 -0700
Subject: [PATCH 7/8] fix typos

---
 src/jsutils/__tests__/suggestionList-test.js | 2 +-
 src/jsutils/suggestionList.js                | 2 +-
 src/validation/rules/FieldsOnCorrectType.js  | 4 +---
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/jsutils/__tests__/suggestionList-test.js b/src/jsutils/__tests__/suggestionList-test.js
index 585431458c..5e4c071be0 100644
--- a/src/jsutils/__tests__/suggestionList-test.js
+++ b/src/jsutils/__tests__/suggestionList-test.js
@@ -21,7 +21,7 @@ describe('suggestionList', () => {
     expect(suggestionList('input', [])).to.deep.equal([]);
   });
 
-  it('Returns options sorted based on simularity', () => {
+  it('Returns options sorted based on similarity', () => {
     expect(suggestionList('abc', [ 'a', 'ab', 'abc' ]))
       .to.deep.equal([ 'abc', 'ab' ]);
   });
diff --git a/src/jsutils/suggestionList.js b/src/jsutils/suggestionList.js
index cc524c17a5..3f9962f87d 100644
--- a/src/jsutils/suggestionList.js
+++ b/src/jsutils/suggestionList.js
@@ -10,7 +10,7 @@
 
 /**
  * Given an invalid input string and a list of valid options, returns a filtered
- * list of valid options sorted based on their simularity with the input.
+ * list of valid options sorted based on their similarity with the input.
  */
 export function suggestionList(
     input: string,
diff --git a/src/validation/rules/FieldsOnCorrectType.js b/src/validation/rules/FieldsOnCorrectType.js
index 9738ec33f2..c9f87c7b7e 100644
--- a/src/validation/rules/FieldsOnCorrectType.js
+++ b/src/validation/rules/FieldsOnCorrectType.js
@@ -49,9 +49,7 @@ export function undefinedFieldMessage(
     if (suggestedFields.length > MAX_LENGTH) {
       suggestions += `, or ${suggestedFields.length - MAX_LENGTH} other field`;
     }
-    message +=
-      ` Did you mean to query ${suggestions}?`;
-
+    message +=` Did you mean to query ${suggestions}?`;
   }
   return message;
 }

From 5a9fb1e743795f56af5b7759f4ed794e29db32ac Mon Sep 17 00:00:00 2001
From: Yuzhi Zheng <yuzhi.z@gmail.com>
Date: Tue, 19 Apr 2016 12:00:28 -0700
Subject: [PATCH 8/8] fix lint

---
 src/validation/rules/FieldsOnCorrectType.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/validation/rules/FieldsOnCorrectType.js b/src/validation/rules/FieldsOnCorrectType.js
index c9f87c7b7e..70a642d362 100644
--- a/src/validation/rules/FieldsOnCorrectType.js
+++ b/src/validation/rules/FieldsOnCorrectType.js
@@ -49,7 +49,7 @@ export function undefinedFieldMessage(
     if (suggestedFields.length > MAX_LENGTH) {
       suggestions += `, or ${suggestedFields.length - MAX_LENGTH} other field`;
     }
-    message +=` Did you mean to query ${suggestions}?`;
+    message += ` Did you mean to query ${suggestions}?`;
   }
   return message;
 }