fix: Control no diff message color with diff options

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - `[jest-jasmine2]` Stop adding `:` after an error that has no message ([#9990](https://github.com/facebook/jest/pull/9990))
+- `[jest-diff]` Control no diff message color with `commonColor` in diff options ([#9997](https://github.com/facebook/jest/pull/9997))
 
 ### Chore & Maintenance
 

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

@@ -249,9 +249,11 @@ exports[`options change color diffStringsUnified 1`] = `
 <g>- changed <b>from</></>
 <r>+ changed <b>to</></>
 <r>+ insert</>
-<d>  common</>
+<y>  common</>
 `;
 
+exports[`options change color no diff 1`] = `<y>Compared values have no visual difference.</>`;
+
 exports[`options change indicators diff 1`] = `
 <g>< Expected</>
 <r>> Received</>

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

@@ -14,13 +14,12 @@ import {diffLinesUnified, diffLinesUnified2} from '../diffLines';
 import {noColor} from '../normalizeDiffOptions';
 import {diffStringsUnified} from '../printDiffs';
 import {DiffOptions} from '../types';
+import {NO_DIFF_MESSAGE} from '../constants';
 
 const optionsCounts: DiffOptions = {
   includeChangeCounts: true,
 };
 
-const NO_DIFF_MESSAGE = 'Compared values have no visual difference.';
-
 // Use only in toBe assertions for edge case messages.
 const stripped = (a: unknown, b: unknown) => stripAnsi(diff(a, b) || '');
 
@@ -975,24 +974,33 @@ describe('options', () => {
   describe('change color', () => {
     const options = {
       changeColor: chalk.bold,
+      commonColor: chalk.yellow,
     };
 
     test('diffStringsUnified', () => {
       const aChanged = a.join('\n').replace('change', 'changed');
       const bChanged = b.join('\n').replace('change', 'changed');
       expect(diffStringsUnified(aChanged, bChanged, options)).toMatchSnapshot();
     });
+
+    test('no diff', () => {
+      expect(diff(a, a, options)).toMatchSnapshot();
+    });
   });
 
   describe('common', () => {
     const options = {
-      commonColor: line => line,
+      commonColor: noColor,
       commonIndicator: '=',
     };
 
     test('diff', () => {
       expect(diff(a, b, options)).toMatchSnapshot();
     });
+
+    test('no diff', () => {
+      expect(diff(a, a, options)).toBe(NO_DIFF_MESSAGE);
+    });
   });
 
   describe('includeChangeCounts false', () => {

packages/jest-diff/src/constants.ts

@@ -5,13 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import chalk = require('chalk');
+export const NO_DIFF_MESSAGE = 'Compared values have no visual difference.';
 
-export const NO_DIFF_MESSAGE = chalk.dim(
-  'Compared values have no visual difference.',
-);
-
-export const SIMILAR_MESSAGE = chalk.dim(
+export const SIMILAR_MESSAGE =
   'Compared values serialize to the same structure.\n' +
-    'Printing internal object structure without calling `toJSON` instead.',
-);
+  'Printing internal object structure without calling `toJSON` instead.';

packages/jest-diff/src/index.ts

@@ -9,6 +9,7 @@ import prettyFormat = require('pretty-format');
 import chalk = require('chalk');
 import getType = require('jest-get-type');
 import {DIFF_DELETE, DIFF_EQUAL, DIFF_INSERT, Diff} from './cleanupSemantic';
+import {normalizeDiffOptions} from './normalizeDiffOptions';
 import {diffLinesRaw, diffLinesUnified, diffLinesUnified2} from './diffLines';
 import {diffStringsRaw, diffStringsUnified} from './printDiffs';
 import {NO_DIFF_MESSAGE, SIMILAR_MESSAGE} from './constants';
@@ -20,6 +21,11 @@ export {diffLinesRaw, diffLinesUnified, diffLinesUnified2};
 export {diffStringsRaw, diffStringsUnified};
 export {DIFF_DELETE, DIFF_EQUAL, DIFF_INSERT, Diff};
 
+const getCommonMessage = (message: string, options?: DiffOptions) => {
+  const {commonColor} = normalizeDiffOptions(options);
+  return commonColor(message);
+};
+
 const {
   AsymmetricMatcher,
   DOMCollection,
@@ -53,7 +59,7 @@ const FALLBACK_FORMAT_OPTIONS_0 = {...FALLBACK_FORMAT_OPTIONS, indent: 0};
 // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
 function diff(a: any, b: any, options?: DiffOptions): string | null {
   if (Object.is(a, b)) {
-    return NO_DIFF_MESSAGE;
+    return getCommonMessage(NO_DIFF_MESSAGE, options);
   }
 
   const aType = getType(a);
@@ -109,7 +115,7 @@ function comparePrimitive(
   const aFormat = prettyFormat(a, FORMAT_OPTIONS);
   const bFormat = prettyFormat(b, FORMAT_OPTIONS);
   return aFormat === bFormat
-    ? NO_DIFF_MESSAGE
+    ? getCommonMessage(NO_DIFF_MESSAGE, options)
     : diffLinesUnified(aFormat.split('\n'), bFormat.split('\n'), options);
 }
 
@@ -128,13 +134,14 @@ function compareObjects(
 ) {
   let difference;
   let hasThrown = false;
+  const noDiffMessage = getCommonMessage(NO_DIFF_MESSAGE, options);
 
   try {
     const aCompare = prettyFormat(a, FORMAT_OPTIONS_0);
     const bCompare = prettyFormat(b, FORMAT_OPTIONS_0);
 
     if (aCompare === bCompare) {
-      difference = NO_DIFF_MESSAGE;
+      difference = noDiffMessage;
     } else {
       const aDisplay = prettyFormat(a, FORMAT_OPTIONS);
       const bDisplay = prettyFormat(b, FORMAT_OPTIONS);
@@ -153,12 +160,12 @@ function compareObjects(
 
   // If the comparison yields no results, compare again but this time
   // without calling `toJSON`. It's also possible that toJSON might throw.
-  if (difference === undefined || difference === NO_DIFF_MESSAGE) {
+  if (difference === undefined || difference === noDiffMessage) {
     const aCompare = prettyFormat(a, FALLBACK_FORMAT_OPTIONS_0);
     const bCompare = prettyFormat(b, FALLBACK_FORMAT_OPTIONS_0);
 
     if (aCompare === bCompare) {
-      difference = NO_DIFF_MESSAGE;
+      difference = noDiffMessage;
     } else {
       const aDisplay = prettyFormat(a, FALLBACK_FORMAT_OPTIONS);
       const bDisplay = prettyFormat(b, FALLBACK_FORMAT_OPTIONS);
@@ -172,8 +179,9 @@ function compareObjects(
       );
     }
 
-    if (difference !== NO_DIFF_MESSAGE && !hasThrown) {
-      difference = SIMILAR_MESSAGE + '\n\n' + difference;
+    if (difference !== noDiffMessage && !hasThrown) {
+      difference =
+        getCommonMessage(SIMILAR_MESSAGE, options) + '\n\n' + difference;
     }
   }