fix(@formatjs/unplugin): add flatten option to match babel-plugin-formatjs ID generation by longlho · Pull Request #6178 · formatjs/formatjs

longlho · 2026-03-23T15:43:32Z

When flatten=true, apply printAST(hoistSelectors(parse(message))) before generating the ID, matching the behavior of babel-plugin-formatjs and the Rust formatjs_cli. Previously the Vite plugin only applied simple whitespace normalization, producing a different hash input and therefore different IDs.

Fixes #6177

Generated with Claude Code

…matjs ID generation When flatten=true, apply printAST(hoistSelectors(parse(message))) before generating the ID, matching the behavior of babel-plugin-formatjs and the Rust formatjs_cli. Previously the Vite plugin only applied simple whitespace normalization, producing a different hash input and therefore different IDs. Fixes #6177 Co-authored-by: Long Ho <longlho@users.noreply.github.com>

longlho

@claude address those comments

longlho · 2026-03-23T15:43:52Z

packages/unplugin/transform.ts

    additionalFunctionNames = [],
    ast: preParseAst = false,
    preserveWhitespace = false,
+    flatten = false,


default to true

longlho · 2026-03-23T15:44:03Z

packages/unplugin/tests/transform.test.ts

+      const input = `<FormattedMessage defaultMessage="Are you sure you want to delete {count,plural,one {this report template} other {these # report templates}}?" />`
+      const result = t(input, {flatten: true})
+      // Hoisted form: plural wraps the full sentence
+      expect(result).toContain(


compare the whole output, not just toContain

claude · 2026-03-23T15:44:30Z

Claude finished @longlho's task in 8m 11s —— View job

Addressed Review Comments

Read review comments
Change flatten default to true in packages/unplugin/transform.ts:54
Update flatten tests to compare whole output with toBe instead of toContain
Commit and push changes

Changes Made

packages/unplugin/transform.ts

Changed flatten = false → flatten = true so flattening is enabled by default, matching babel-plugin-formatjs and Rust CLI behavior out of the box

packages/unplugin/tests/transform.test.ts

Added import {interpolateName} from '@formatjs/ts-transformer'
Test 1 (normalizes ICU format...): replaced two toContain checks with a single toBe comparing the full output string (<FormattedMessage id="14X+wqft" defaultMessage="..." />)
Test 2 (hoists select/plural patterns...): replaced toContain with toBe comparing the full output; uses interpolateName to dynamically compute the expected id from the known flattened message so the assertion remains self-consistent without a magic constant
|

…assertions in tests - Change `flatten` option default from `false` to `true` to match babel-plugin-formatjs and Rust CLI behavior out of the box - Update flatten tests to use `toBe` for whole-output assertions instead of multiple `toContain` checks Co-authored-by: Long Ho <longlho@users.noreply.github.com>

longlho · 2026-03-23T16:54:45Z

@claude add conformance integration tests to check between formatjs_cli and our vite plugin to make sure default set of options matches. Make sure to bazel it

claude · 2026-03-23T16:55:00Z

Claude finished @longlho's task in 7m 55s —— View job

Adding Conformance Integration Tests

Explore existing conformance test structure
Explore unplugin and formatjs_cli codebases
Design conformance test approach
Create packages/unplugin/conformance-tests/rust-binary-utils.ts
Create packages/unplugin/conformance-tests/cli-unplugin-conformance.test.ts
Update packages/unplugin/BUILD.bazel (copy_file + new vitest target)
CI running bazel test //packages/unplugin:conformance_test

What was added

packages/unplugin/conformance-tests/cli-unplugin-conformance.test.ts

7 test cases that each:

Write source code to a temp .tsx file
Run formatjs_cli extract --flatten → collect the JSON-keyed IDs
Run transform(code, tempFile, {}) with default options (flatten=true) → extract id:"..." / id="..." from the output
Assert both ID sets are identical

Test cases:

Plain formatMessage without description
Plain formatMessage with description
Plural message — flatten hoists selectors
Plural embedded in sentence — flatten produces full phrases
JSX <FormattedMessage> with description
defineMessages with multiple messages
Whitespace normalization before ID generation

packages/unplugin/BUILD.bazel

Added copy_file rule to copy the Rust CLI binary into the package (same pattern as packages/cli/integration-tests)
Added conformance_test vitest target with data = ["//crates/formatjs_cli"] and @bazel/runfiles dep
|

Verify that formatjs_cli extract --flatten and the unplugin transform (default options: flatten=true) generate identical IDs for the same source, ensuring extraction and bundling pipelines stay in sync. Co-authored-by: Long Ho <longlho@users.noreply.github.com>

lensbart · 2026-03-23T17:20:06Z

Thanks for the lightning-fast fix & release! ❤️

longlho commented Mar 23, 2026

View reviewed changes

longlho merged commit 9cc3087 into main Mar 23, 2026
6 checks passed

longlho deleted the claude/issue-6177-20260323-1535 branch March 23, 2026 17:11

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fix(@formatjs/unplugin): add flatten option to match babel-plugin-formatjs ID generation#6178

fix(@formatjs/unplugin): add flatten option to match babel-plugin-formatjs ID generation#6178
longlho merged 3 commits intomainfrom
claude/issue-6177-20260323-1535

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