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 |