feat: add optional configurable JSX placeholder naming by mogelbrod · Pull Request #207 · lingui/swc-plugin

mogelbrod · 2026-04-09T11:54:19Z

Description

SWC implementation of lingui/js-lingui#2505

Add a new feature that allows developers to customize the identifiers of JSX placeholders generated by the <Trans> macro. This results in placeholder identifiers in extracted messages that are more stable, human-readable, and contextual, instead of the default arbitrary numeric indices (e.g., replacing <0> with <em> or <link>).

It is accomplished via two new optional configuration options (via lingui.config.js in the macro options):

jsxPlaceholderAttribute: Allows defining a custom prop name (e.g., _t) that can be used on components to set an explicit placeholder name locally.
jsxPlaceholderDefaults: Allows providing a record of tag names to placeholder names, enabling global default renaming for specific JSX components.

Types of changes

Bugfix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
Documentation update
Examples update

Fixes #1188

Checklist

I have read the CONTRIBUTING and CODE_OF_CONDUCT docs
I have added tests that prove my fix is effective or that my feature works
I have added the necessary documentation (if appropriate) - will do before merging

Disclaimer

Much of this PR was generated by Copilot using the Gemini 3.1 Pro (Preview) model with training/sharing disabled.

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Pull request overview

Adds optional configuration for more stable, human-readable JSX placeholder identifiers generated from <Trans> JSX, aligning the SWC plugin behavior with LinguiJS’ macro feature request.

Changes:

Introduces jsxPlaceholderAttribute and jsxPlaceholderDefaults options and threads them into message building.
Updates MessageBuilder to emit named JSX placeholders (with suffixing for collisions) and strip the naming attribute from generated component AST.
Adds JSX fixture tests and snapshot outputs covering named placeholders, defaults, deduplication, and prop-order scenarios.

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Regenerated lockfile (currently switched to Yarn v1 format).
tests/jsx.rs	Adds new test cases for named JSX placeholders and dedup/suffix behavior.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_basic.js	Snapshot for `_t`-driven placeholder naming.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_stripped_ast.js	Snapshot verifying `_t` attribute stripping from emitted component AST.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_defaults.js	Snapshot for global defaults-based placeholder naming.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_deduplication_different_props.js	Snapshot for suffixing when same placeholder name has different props.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_deduplication_identical.js	Snapshot for deduplication when same placeholder name + identical props repeats.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_deduplication_with_stripped_props.js	Snapshot for deduplication when `_t` is stripped and props determine equality.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_attribute_ignored_when_not_configured.js	Snapshot ensuring `_t` is ignored unless configured.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_prop_order.js	Snapshot for behavior when same props appear in different orders.
tests/swc_snapshots/tests/jsx.rs/jsx_named_placeholders_prop_order2.js	Snapshot for behavior when props differ.
src/options.rs	Adds new options to config struct, normalization, and defaults.
src/lib.rs	Passes options into `MessageBuilder::parse` and simplifies replacer handling.
src/js_macro_folder.rs	Passes options into `MessageBuilder::parse` for JS macro paths.
src/builder.rs	Implements placeholder naming logic, dedup/suffixing, and `_t` attr stripping.

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mogelbrod · 2026-04-16T08:11:38Z

Note that this PR hasn't been updated to align with the changes in lingui/js-lingui#2505 - will do so once the final API has been decided.

andrii-bodnar · 2026-04-17T08:08:27Z

@mogelbrod could you please align this PR with the final Babel version? Thanks!

…ersion

mogelbrod · 2026-04-17T09:00:23Z

@andrii-bodnar I've pushed a commit that aligns this SWC implementation with lingui/js-lingui#2505

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Pull request overview

Copilot reviewed 20 out of 21 changed files in this pull request and generated 1 comment.

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Pull request overview

Copilot reviewed 20 out of 21 changed files in this pull request and generated 1 comment.

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andrii-bodnar · 2026-04-17T11:51:11Z

@mogelbrod thank you! Please also check failing CI/CD pipelines

codecov · 2026-04-17T12:42:58Z

Codecov Report

❌ Patch coverage is 96.27329% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.83%. Comparing base (5f673bd) to head (219a9c0).
⚠️ Report is 1 commits behind head on next.

Files with missing lines	Patch %	Lines
src/builder.rs	95.38%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next     #207      +/-   ##
==========================================
+ Coverage   92.59%   92.83%   +0.24%     
==========================================
  Files           8        8              
  Lines        1444     1578     +134     
==========================================
+ Hits         1337     1465     +128     
- Misses        107      113       +6

Flag	Coverage Δ
unittests	`92.83% <96.27%> (+0.24%)`	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/js_macro_folder.rs	`97.70% <100.00%> (ø)`
src/lib.rs	`91.72% <100.00%> (-0.05%)`	⬇️
src/options.rs	`100.00% <100.00%> (ø)`
src/builder.rs	`97.26% <95.38%> (-1.65%)`	⬇️

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andrii-bodnar · 2026-04-17T12:54:20Z

@mogelbrod It looks like the yarn.lock file was unnecessarily modified in this PR, causing the "E2E Smoke Test" to fail

mogelbrod · 2026-04-17T13:15:14Z

@mogelbrod It looks like the yarn.lock file was unnecessarily modified in this PR, causing the "E2E Smoke Test" to fail

Thanks! I've checked out the version from next. mise wasn't picking up the yarn version from package.json - after installing the correct yarn version I get the correct yarn.lock output.

feat: add optional configurable JSX placeholder naming

12fb115

This was referenced Apr 9, 2026

feat: add optional configurable JSX placeholder naming lingui/js-lingui#2505

Merged

Allow named components in Trans in @lingui/macro lingui/js-lingui#1188

Closed

andrii-bodnar requested a review from Copilot April 16, 2026 07:46

Copilot started reviewing on behalf of andrii-bodnar April 16, 2026 07:46 View session

Copilot AI reviewed Apr 16, 2026

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Comment thread src/builder.rs Outdated

Comment thread src/builder.rs

Comment thread src/options.rs

refactor: update JSX placeholder name functionality to mirror babel v…

000b96a

…ersion

test: add configuration deserialization test for jsx placeholder fields

52af023

mogelbrod requested a review from Copilot April 17, 2026 09:09

Copilot started reviewing on behalf of mogelbrod April 17, 2026 09:10 View session

Copilot AI reviewed Apr 17, 2026

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Comment thread src/builder.rs

perf: compile placeholder validation regexes only once using Lazy

08f2132

mogelbrod requested a review from Copilot April 17, 2026 09:34

Copilot started reviewing on behalf of mogelbrod April 17, 2026 09:34 View session

Copilot AI reviewed Apr 17, 2026

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Comment thread src/builder.rs

mogelbrod added 2 commits April 17, 2026 14:34

style: run cargo fmt

99b4bec

style: fix cargo clippy issues

5de1353

docs: Mention new settings in README

93b6176

mogelbrod added 2 commits April 17, 2026 15:03

test: add additional tests to improve test coverage

a5018ad

build: restore original yarn.lock file

219a9c0

andrii-bodnar approved these changes Apr 17, 2026

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andrii-bodnar merged commit f4b674d into lingui:next Apr 17, 2026
4 checks passed

andrii-bodnar pushed a commit that referenced this pull request Apr 17, 2026

feat: add optional configurable JSX placeholder naming (#207)

1be1aff

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