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fix(snapshot): increase default snapshot max output length (#10150)
Co-authored-by: Codex <noreply@openai.com>
authored by
Hiroshi Ogawa
Codex
and committed by
GitHub
(Apr 15, 2026, 8:23 AM +0200)
21e66ff6
bb4829ad
+87
+3
packages/pretty-format/USAGE.md
+3
packages/pretty-format/USAGE.md
···
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- `escapeString: false`
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- `escapeRegex: true`
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- `printFunctionName: false`
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- `maxOutputLength: 2 ** 27`
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Snapshots use a more generous safety cap than the package default. The default `maxOutputLength` is tuned for general-purpose formatting such as logs and error messages, while snapshot users may intentionally persist large serialized values to dedicated files. Users can still opt into a smaller cap through `test.snapshotFormat.maxOutputLength`.
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Default snapshot plugin stack:
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+80
test/snapshots/test/options.test.ts
+80
test/snapshots/test/options.test.ts
···
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import { describe, expect, test } from 'vitest'
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import { runInlineTests } from '../../test-utils'
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describe('maxOutputLength', () => {
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test('default', async () => {
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const result = await runInlineTests(
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{
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'basic.test.ts': `
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import { expect, test } from 'vitest'
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test('large snapshot', () => {
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expect(Array.from({ length: 500_000 }, (_, i) => ({ i }))).toMatchSnapshot()
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})
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`,
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},
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{
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update: 'all',
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},
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)
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expect(result.stderr).toMatchInlineSnapshot(`""`)
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const snapshot = result.fs.readFile('__snapshots__/basic.test.ts.snap')
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expect(snapshot.slice(-50)).toMatchInlineSnapshot(`
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" "i": 499998,
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},
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{
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"i": 499999,
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},
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]
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\`;
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"
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`)
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expect(snapshot.length).toMatchInlineSnapshot(`12888992`)
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})
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test('override', async () => {
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const result = await runInlineTests(
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{
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'basic.test.ts': `
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import { expect, test } from 'vitest'
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test('large snapshot', () => {
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expect(Array.from({ length: 8 }, (_, i) => ({ i }))).toMatchSnapshot()
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})
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`,
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},
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{
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update: 'all',
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snapshotFormat: {
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maxOutputLength: 50,
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},
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},
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)
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expect(result.stderr).toMatchInlineSnapshot(`""`)
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expect(result.fs.readFile('__snapshots__/basic.test.ts.snap')).toMatchInlineSnapshot(`
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"// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
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exports[\`large snapshot 1\`] = \`
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[
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{
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"i": 0,
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},
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{
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"i": 1,
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},
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{
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"i": 2,
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},
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[Object],
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[Object],
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[Object],
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[Object],
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[Object],
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]
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\`;
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"
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`)
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})
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})
+4
packages/snapshot/src/port/state.ts
+4
packages/snapshot/src/port/state.ts
···
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this._snapshotFormat = {
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printBasicPrototype: false,
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escapeString: false,
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// more generous safety cap 128MB (same as Node's util.inspect)
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// instead of tighter pretty-format default 1MB
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// since users can purposely save large snapshot to a dedicated file.
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maxOutputLength: 2 ** 27,
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...options.snapshotFormat,
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}
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this._environment = options.snapshotEnvironment