Adds options for configuring the snapshot and inline snapshot serializers

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[jest-cli]` Adds a new config options `snapshotFormat` which offers a way to override any of the formatting settings which come with [pretty-format](https://www.npmjs.com/package/pretty-format#usage-with-options). ([#11654](https://github.com/facebook/jest/pull/11654))
+
 ### Fixes
 
 - `[jest-environment-node]` Add `Event` and `EventTarget` to node global environment. ([#11705](https://github.com/facebook/jest/issues/11705))

docs/Configuration.md

@@ -945,6 +945,41 @@ Default: `5`
 
 The number of seconds after which a test is considered as slow and reported as such in the results.
 
+### `snapshotFormat` \[object]
+
+Default: `undefined`
+
+Allows overriding specific snapshot formatting options documented in the [pretty-format readme](https://www.npmjs.com/package/pretty-format#usage-with-options). For example, this config would have the snapshot formatter not print a prefix for "Object" and "Array":
+
+```json
+{
+  "jest": {
+    "snapshotFormat": {
+      "printBasicPrototype": false
+    }
+  }
+}
+```
+
+```ts
+import {expect, test} from '@jest/globals';
+
+test('does not show prototypes for object and array inline', () => {
+  const object = {
+    array: [{hello: 'Danger'}],
+  };
+  expect(object).toMatchInlineSnapshot(`
+{
+  "array": [
+    {
+      "hello": "Danger",
+    },
+  ],
+}
+    `);
+});
+```
+
 ### `snapshotResolver` \[string]
 
 Default: `undefined`

e2e/snapshot-formatting-changes/__tests__/__snapshots__/snapshot.test.js.snap

@@ -0,0 +1,11 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`snapshot serializer uses 8 chars for indent, and shows no prototypes for object and array in a snapshot: no prototypes 1`] = `
+{
+        "array": [
+                {
+                        "hello": "Danger",
+                },
+        ],
+}
+`;

e2e/snapshot-formatting-changes/__tests__/snapshot.test.js

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+'use strict';
+
+describe('snapshot serializer', () => {
+  it('does not show prototypes for object and array inline', () => {
+    const object = {
+      array: [{hello: 'Danger'}],
+    };
+    expect(object).toMatchInlineSnapshot(`
+{
+        "array": [
+                {
+                        "hello": "Danger",
+                },
+        ],
+}
+`);
+  });
+
+  it('uses 8 chars for indent, and shows no prototypes for object and array in a snapshot', () => {
+    const object = {
+      array: [{hello: 'Danger'}],
+    };
+    expect(object).toMatchSnapshot('no prototypes');
+  });
+});

e2e/snapshot-formatting-changes/package.json

@@ -0,0 +1,9 @@
+{
+  "jest": {
+    "testEnvironment": "node",
+    "snapshotFormat": {
+      "printBasicPrototype": false,
+      "indent": 8
+    }
+  }
+}

packages/jest-circus/src/legacy-code-todo-rewrite/jestAdapterInit.ts

@@ -156,6 +156,7 @@ export const initialize = async ({
   const snapshotState = new SnapshotState(snapshotPath, {
     expand,
     prettierPath: config.prettierPath,
+    snapshotFormat: config.snapshotFormat,
     updateSnapshot,
   });
   // @ts-expect-error: snapshotState is a jest extension of `expect`

packages/jest-config/src/ValidConfig.ts

@@ -8,6 +8,7 @@
 import type {Config} from '@jest/types';
 import {replacePathSepForRegex} from 'jest-regex-util';
 import {multipleValidOptions} from 'jest-validate';
+import {DEFAULT_OPTIONS as PRETTY_FORMAT_DEFAULTS} from 'pretty-format';
 import {NODE_MODULES} from './constants';
 
 const NODE_MODULES_REGEXP = replacePathSepForRegex(NODE_MODULES);
@@ -109,6 +110,7 @@ const initialOptions: Config.InitialOptions = {
   skipFilter: false,
   skipNodeResolution: false,
   slowTestThreshold: 5,
+  snapshotFormat: PRETTY_FORMAT_DEFAULTS,
   snapshotResolver: '<rootDir>/snapshotResolver.js',
   snapshotSerializers: ['my-serializer-module'],
   testEnvironment: 'jest-environment-jsdom',

packages/jest-config/src/index.ts

@@ -149,6 +149,7 @@ const groupOptions = (
     runTestsByPath: options.runTestsByPath,
     silent: options.silent,
     skipFilter: options.skipFilter,
+    snapshotFormat: options.snapshotFormat,
     testFailureExitCode: options.testFailureExitCode,
     testNamePattern: options.testNamePattern,
     testPathPattern: options.testPathPattern,
@@ -204,6 +205,7 @@ const groupOptions = (
     skipFilter: options.skipFilter,
     skipNodeResolution: options.skipNodeResolution,
     slowTestThreshold: options.slowTestThreshold,
+    snapshotFormat: options.snapshotFormat,
     snapshotResolver: options.snapshotResolver,
     snapshotSerializers: options.snapshotSerializers,
     testEnvironment: options.testEnvironment,

packages/jest-config/src/normalize.ts

@@ -997,6 +997,7 @@ export default async function normalize(
       case 'skipFilter':
       case 'skipNodeResolution':
       case 'slowTestThreshold':
+      case 'snapshotFormat':
       case 'testEnvironment':
       case 'testEnvironmentOptions':
       case 'testFailureExitCode':

packages/jest-core/src/lib/__tests__/__snapshots__/logDebugMessages.test.ts.snap

@@ -41,6 +41,7 @@ exports[`prints the config object 1`] = `
     "skipFilter": false,
     "skipNodeResolution": false,
     "slowTestThreshold": 5,
+    "snapshotFormat": {},
     "snapshotSerializers": [],
     "testEnvironment": "node",
     "testEnvironmentOptions": {},
@@ -94,6 +95,7 @@ exports[`prints the config object 1`] = `
     "runTestsByPath": false,
     "silent": false,
     "skipFilter": false,
+    "snapshotFormat": {},
     "testFailureExitCode": 1,
     "testNamePattern": "",
     "testPathPattern": "",

packages/jest-jasmine2/src/setup_jest_globals.ts

@@ -106,12 +106,13 @@ export default async ({
 
   patchJasmine();
   const {expand, updateSnapshot} = globalConfig;
-  const {prettierPath} = config;
+  const {prettierPath, snapshotFormat} = config;
   const snapshotResolver = await buildSnapshotResolver(config, localRequire);
   const snapshotPath = snapshotResolver.resolveSnapshotPath(testPath);
   const snapshotState = new SnapshotState(snapshotPath, {
     expand,
     prettierPath,
+    snapshotFormat,
     updateSnapshot,
   });
   // @ts-expect-error: snapshotState is a jest extension of `expect`

packages/jest-snapshot/src/State.ts

@@ -8,6 +8,7 @@
 import * as fs from 'graceful-fs';
 import type {Config} from '@jest/types';
 import {getStackTraceLines, getTopFrame} from 'jest-message-util';
+import type {OptionsReceived as PrettyFormatOptions} from 'pretty-format';
 import {InlineSnapshot, saveInlineSnapshots} from './InlineSnapshots';
 import type {SnapshotData} from './types';
 import {
@@ -25,6 +26,7 @@ export type SnapshotStateOptions = {
   updateSnapshot: Config.SnapshotUpdateState;
   prettierPath: Config.Path;
   expand?: boolean;
+  snapshotFormat: PrettyFormatOptions;
 };
 
 export type SnapshotMatchOptions = {
@@ -61,6 +63,7 @@ export default class SnapshotState {
   private _inlineSnapshots: Array<InlineSnapshot>;
   private _uncheckedKeys: Set<string>;
   private _prettierPath: Config.Path;
+  private _snapshotFormat: PrettyFormatOptions;
 
   added: number;
   expand: boolean;
@@ -88,6 +91,7 @@ export default class SnapshotState {
     this.unmatched = 0;
     this._updateSnapshot = options.updateSnapshot;
     this.updated = 0;
+    this._snapshotFormat = options.snapshotFormat;
   }
 
   markSnapshotsAsCheckedForTest(testName: string): void {
@@ -201,7 +205,9 @@ export default class SnapshotState {
       this._uncheckedKeys.delete(key);
     }
 
-    const receivedSerialized = addExtraLineBreaks(serialize(received));
+    const receivedSerialized = addExtraLineBreaks(
+      serialize(received, undefined, this._snapshotFormat),
+    );
     const expected = isInline ? inlineSnapshot : this._snapshotData[key];
     const pass = expected === receivedSerialized;
     const hasSnapshot = expected !== undefined;

packages/jest-snapshot/src/utils.ts

@@ -10,7 +10,10 @@ import chalk = require('chalk');
 import * as fs from 'graceful-fs';
 import naturalCompare = require('natural-compare');
 import type {Config} from '@jest/types';
-import {format as prettyFormat} from 'pretty-format';
+import {
+  OptionsReceived as PrettyFormatOptions,
+  format as prettyFormat,
+} from 'pretty-format';
 import {getSerializers} from './plugins';
 import type {SnapshotData} from './types';
 
@@ -152,13 +155,18 @@ export const removeLinesBeforeExternalMatcherTrap = (stack: string): string => {
 const escapeRegex = true;
 const printFunctionName = false;
 
-export const serialize = (val: unknown, indent = 2): string =>
+export const serialize = (
+  val: unknown,
+  indent = 2,
+  formatOverrides: PrettyFormatOptions = {},
+): string =>
   normalizeNewlines(
     prettyFormat(val, {
       escapeRegex,
       indent,
       plugins: getSerializers(),
       printFunctionName,
+      ...formatOverrides,
     }),
   );