Update pretty-format and use it for diffs; update snapshot printing; …

…print without toJSON if objects appear similar.

packages/jest-diff/package.json

@@ -11,7 +11,7 @@
     "chalk": "^1.1.3",
     "diff": "^3.0.0",
     "jest-matcher-utils": "^15.1.0",
-    "pretty-format": "~4.0.0"
+    "pretty-format": "~4.2.1"
   },
   "scripts": {
     "test": "../../packages/jest-cli/bin/jest.js"

packages/jest-diff/src/__tests__/__snapshots__/diff-test.js.snap

@@ -0,0 +1,13 @@
+exports[`test falls back to not call toJSON if objects look identical 1`] = `
+"Compared values serialize to the same structure.
+Printing internal object structure without calling \`toJSON\` instead.
+
+- Expected
++ Received
+
+  Object {
+-   \"line\": 1,
++   \"line\": 2,
+    \"toJSON\": [Function toJSON],
+  }"
+`;

packages/jest-diff/src/__tests__/diff-test.js

@@ -54,7 +54,7 @@ describe('no visual difference', () => {
       `'${JSON.stringify(values[0])}' and '${JSON.stringify(values[1])}'`,
       () => {
         expect(stripAnsi(diff(values[0], values[1]))).toBe(
-          'Compared values have no visual difference',
+          'Compared values have no visual difference.',
         );
       },
     );
@@ -68,6 +68,12 @@ test('oneline strings', () => {
   expect(stripAnsi(diff('123456789', '234567890'))).toBe(null);
 });
 
+test('falls back to not call toJSON if objects look identical', () => {
+  const a = {toJSON: () => 'foo', line: 1};
+  const b = {toJSON: () => 'foo', line: 2};
+  expect(diff(a, b)).toMatchSnapshot();
+});
+
 test('multiline strings', () => {
   const result = diff(
 `line 1

packages/jest-diff/src/constants.js

@@ -12,5 +12,11 @@
 
 const chalk = require('chalk');
 
-module.exports.NO_DIFF_MESSAGE =
-  chalk.dim.underline('Compared values have no visual difference');
+exports.NO_DIFF_MESSAGE =
+  chalk.dim('Compared values have no visual difference.');
+
+exports.SIMILAR_MESSAGE =
+  chalk.dim(
+    'Compared values serialize to the same structure.\n' +
+    'Printing internal object structure without calling `toJSON` instead.',
+  );

packages/jest-diff/src/diffStrings.js

@@ -25,7 +25,7 @@ const getAnnotation = options =>
   chalk.red('+ ' + ((options && options.bAnnotation) || 'Received')) + '\n\n';
 
 // diff characters if oneliner and diff lines if multiline
-function diffStrings(a: string, b: string, options: ?DiffOptions): ?string {
+function diffStrings(a: string, b: string, options: ?DiffOptions): string {
   let isDifferent = false;
 
   // `diff` uses the Myers LCS diff algorithm which runs in O(n+d^2) time

packages/jest-diff/src/index.js

@@ -20,8 +20,19 @@ const diffStrings = require('./diffStrings');
 const {getType} = require('jest-matcher-utils');
 const prettyFormat = require('pretty-format');
 
-const jsxLikePlugins = [ReactTestComponentPlugin, ReactElementPlugin];
-const NO_DIFF_MESSAGE = require('./constants').NO_DIFF_MESSAGE;
+const {
+  NO_DIFF_MESSAGE,
+  SIMILAR_MESSAGE,
+} = require('./constants');
+
+const PLUGINS = [ReactTestComponentPlugin, ReactElementPlugin];
+const FORMAT_OPTIONS = {
+  plugins: PLUGINS,
+};
+const FALLBACK_FORMAT_OPTIONS = {
+  callToJSON: false,
+  plugins: PLUGINS,
+};
 
 // Generate a string that will highlight the difference between two values
 // with green and red. (similar to how github does code diffing)
@@ -49,10 +60,24 @@ function diff(a: any, b: any, options: ?DiffOptions): ?string {
     case 'boolean':
       return null;
     default:
-      return diffStrings(
-        prettyFormat(a, {plugins: jsxLikePlugins}, options),
-        prettyFormat(b, {plugins: jsxLikePlugins}, options),
+      let diffMessage = diffStrings(
+        prettyFormat(a, FORMAT_OPTIONS),
+        prettyFormat(b, FORMAT_OPTIONS),
+        options,
       );
+      // If the comparison yields no results, compare again but this time
+      // without calling `toJSON`.
+      if (diffMessage === NO_DIFF_MESSAGE) {
+        diffMessage = diffStrings(
+          prettyFormat(a, FALLBACK_FORMAT_OPTIONS),
+          prettyFormat(b, FALLBACK_FORMAT_OPTIONS),
+          options,
+        );
+        if (diffMessage !== NO_DIFF_MESSAGE) {
+          diffMessage = SIMILAR_MESSAGE + '\n\n' + diffMessage;
+        }
+      }
+      return diffMessage;
   }
 }
 

packages/jest-matcher-utils/package.json

@@ -12,6 +12,7 @@
     "test": "../../packages/jest-cli/bin/jest.js"
   },
   "dependencies": {
-    "chalk": "^1.1.3"
+    "chalk": "^1.1.3",
+    "pretty-format": "~4.2.1"
   }
 }

packages/jest-matcher-utils/src/__tests__/index-test.js

@@ -14,19 +14,19 @@ const {stringify, getType} = require('../');
 
 describe('.stringify()', () => {
   [
-    [[], '[]'],
+    [[], 'Array []'],
     [{}, '{}'],
     [1, '1'],
     [0, '0'],
     [1.5, '1.5'],
     [null, 'null'],
-    [undefined, '"undefined"'],
+    [undefined, 'undefined'],
     ['abc', '"abc"'],
-    [Symbol.for('abc'), '"Symbol(abc)"'],
-    [NaN, '"NaN"'],
-    [Infinity, '"Infinity"'],
-    [-Infinity, '"-Infinity"'],
-    [/ab\.c/gi, '"/ab\\\\.c/gi"'],
+    [Symbol.for('abc'), 'Symbol(abc)'],
+    [NaN, 'NaN'],
+    [Infinity, 'Infinity'],
+    [-Infinity, '-Infinity'],
+    [/ab\.c/gi, '/ab\\.c/gi'],
   ].forEach(([v, s]) => {
     test(stringify(v), () => {
       expect(stringify(v)).toBe(s);
@@ -36,7 +36,7 @@ describe('.stringify()', () => {
   test('circular references', () => {
     const a = {};
     a.a = a;
-    expect(stringify(a)).toBe('{"a":"[Circular]"}');
+    expect(stringify(a)).toBe('{"a": [Circular]}');
   });
 
   test('toJSON error', () => {
@@ -45,12 +45,13 @@ describe('.stringify()', () => {
         throw new Error('Nope.');
       },
     };
-    expect(stringify(evil)).toBe('[object]');
-    expect(stringify({a: {b: {evil}}})).toBe('[object]');
+    expect(stringify(evil)).toBe('{"toJSON": [Function toJSON]}');
+    expect(stringify({a: {b: {evil}}}))
+      .toBe('{"a": {"b": {"evil": {"toJSON": [Function toJSON]}}}}');
 
     function Evil() {}
     Evil.toJSON = evil.toJSON;
-    expect(stringify(Evil)).toBe('function Evil() {}');
+    expect(stringify(Evil)).toBe('[Function Evil]');
   });
 });
 
@@ -66,5 +67,4 @@ describe('.getType()', () => {
   test('boolean', () => expect(getType(true)).toBe('boolean'));
   test('symbol', () => expect(getType(Symbol.for('a'))).toBe('symbol'));
   test('regexp', () => expect(getType(/abc/)).toBe('regexp'));
-
 });

packages/jest-matcher-utils/src/index.js

@@ -11,6 +11,7 @@
 'use strict';
 
 const chalk = require('chalk');
+const prettyFormat = require('pretty-format');
 
 export type ValueType =
   | 'array'
@@ -74,68 +75,10 @@ const getType = (value: any): ValueType => {
   throw new Error(`value of unknown type: ${value}`);
 };
 
-const stringifyValue = (value, visitedSet) => {
-  if (value instanceof Error) {
-    const name = (value.constructor && value.constructor.name) || 'Error';
-    return `${name}: ${value.message}`;
-  } else if (typeof value === 'object' && value !== null) {
-    if (
-      value &&
-      value.constructor &&
-      value.constructor.name === 'RegExp'
-    ) {
-      return value.toString();
-    } else {
-      if (visitedSet.has(value)) {
-        return '[Circular]';
-      }
-      visitedSet.add(value);
-    }
-  } else if (typeof value === 'function') {
-    return value.toString();
-  } else if (typeof value === 'undefined') {
-    return 'undefined';
-  // $FlowFixMe symbols are not supported by flow yet
-  } else if (typeof value === 'symbol') {
-    return value.toString();
-  } else if (value === Infinity) {
-    return 'Infinity';
-  } else if (value === -Infinity) {
-    return '-Infinity';
-  } else if (Number.isNaN(value)) {
-    return 'NaN';
-  }
-  return value;
-};
-
-const stringifyDeep = obj => {
-  const visitedSet = new Set();
-  let result = null;
-  try {
-    result = JSON.stringify(
-      obj,
-      (_, value) => stringifyValue(value, visitedSet),
-    );
-  } catch (err) { }
-  return typeof result === 'string' ? result : null;
-};
-
-const stringifyShallow = obj => {
-  let result = null;
-  try {
-    result = stringifyValue(obj, new Set());
-  } catch (err) {}
-  return typeof result === 'string' ? result : null;
-};
-
-// Convert to JSON removing circular references and
-// converting JS values to strings.
-const stringify = (obj: any): string => {
-  return (
-    stringifyDeep(obj) ||
-    stringifyShallow(obj) ||
-    '[' + typeof obj + ']'
-  );
+const stringify = (object: any): string => {
+  return prettyFormat(object, {
+    min: true,
+  });
 };
 
 const printReceived = (object: any) => RECEIVED_COLOR(stringify(object));