FormatJS Plugin doesn't support string concatenation

[vu-dao-93]

I'm using the @swc/plugin-formatjs to transform react intl messages, and I face an error for message that have string concatenation

const message = defineMessage({
  defaultMessage: 'Hello ' + 'world'
});

the result would be

const message = defineMessage({
  defaultMessage: []
});

And throw this error

Error: Uncaught [Error: [@formatjs/intl] An `id` must be provided to format a message

I found this issue (formatjs/formatjs#2252) in formatjs, which indicates that string concatenation should be supported for defaultMessage. I think it should be added here as well?

[vu-dao-93]

Looking at the transform file I can see that string concatenation is supported for the description field, but not for defaultMessage, is there a reason for that?

[kdy1]

@claude Fix this issue and create a PR

[claude]

Claude finished @kdy1's task —— View job • claude/issue-532-20251117-1607 • Create PR ➔

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Fixed FormatJS string concatenation issue ✅

Tasks

• Read repository setup instructions (CLAUDE.md)
• Examine the current implementation in the transform file
• Understand how string concatenation works for description field
• Apply the same logic to defaultMessage field
• Build the plugin
• Test the changes
• Commit and push changes
• Provide PR creation link

Summary

Successfully fixed issue #532 where string concatenation in defaultMessage fields was not working properly. The plugin now correctly handles expressions like:

const message = defineMessage({
  defaultMessage: 'Hello ' + 'world'
});

Root Cause

The description field was using resolution-aware methods that properly handle binary expressions (string concatenation), but defaultMessage was using simpler methods without this support, causing concatenated strings to be lost or transformed into empty arrays.

Changes Made

1. Added new visitor methods with resolution-aware binary expression evaluation:

   • get_jsx_icu_message_value() - for JSX attributes (with template literal support)
   • get_call_expr_icu_message_value() - for call expressions

2. Enhanced template literal support in get_call_expr_message_descriptor_value_maybe_object_with_resolution()

3. Updated message evaluation functions to use the new resolution-aware methods:

   • evaluate_jsx_message_descriptor_with_visitor()
   • evaluate_call_expr_message_descriptor_with_visitor()

4. Removed unused standalone functions to clean up the codebase

Test Results

All 19 tests passing ✅, including:

• ✅ should handle string concatenation in defaultMessage
• ✅ should handle multiple string concatenations
• ✅ should handle string concatenation in FormattedMessage JSX
• ✅ should quote plural keys correctly when ast enabled (template literals)

Create Pull Request

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Branch: claude/issue-532-20251117-1607 |

[cuyl]

I can't reproduce this issue, hopefully #567 can resolve the issue.

[kdy1]

@claude Fix this PR by adding tests to ensure that this issue is fixed

[claude]

Claude finished @kdy1's task in 7m 28s —— View job • claude/issue-532-20260321-0027 • Create PR ➔

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Adding Tests for String Concatenation in FormatJS Plugin

Tasks

• Read CLAUDE.md for setup instructions
• Examine existing tests for the formatjs plugin
• Understand the current implementation
• Build the WASM plugin and run tests to verify current state
• Add explicit regression test for issue FormatJS Plugin doesn't support string concatenation #532
• Commit and push changes

Summary

The string concatenation issue (#532) is already fixed in the current codebase — the implementation correctly uses evaluate_expr() with the SWC evaluator which handles binary + expressions.

The existing test suite already covered string concatenation in defaultMessage with tests like "Foo " + "Bar". I added one additional explicit regression test that reproduces the exact code from the issue:

const message = defineMessage({
  defaultMessage: 'Hello ' + 'world'
});

This test verifies:

• A valid id is generated
• defaultMessage becomes "Hello world" (concatenated)
• The result is not an empty array ([]) — the exact failure mode described in the issue

All 22 tests pass ✅ (previously 21, now with the new regression test).

| Branch: claude/issue-532-20260321-0027