fix(isolated-declarations): incorrect nested namespace output in isolated declarations

[Copilot]

Dotted namespace syntax export namespace X.Y.Z {} was incorrectly transformed to export declare namespace Y.Z.Z {} instead of export declare namespace X.Y.Z {}.

Root cause: Variable shadowing in transform_ts_module_declaration. When processing nested TSModuleDeclaration bodies, the pattern match variable decl shadowed the function parameter, causing the inner namespace name to be used instead of the outer one.

Changes:

• Renamed pattern match variable from decl to inner_decl to preserve access to outer declaration's identifier
• Added test coverage for dotted namespace syntax with varying nesting depths

Example:

// Input
export namespace X.Y.Z {}

// Before: Y.Z.Z (incorrect)
// After: X.Y.Z (correct)
export declare namespace X.Y.Z {
  export {};
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Isolated declarations: Incorrect output for nested namespace</issue_title>
<issue_description>Input:

//               _____
export namespace X.Y.Z {}

Isolated declarations output:

//                       _____
export declare namespace Y.Z.Z {
  export {};
}

Playground

Maybe this code is the cause?

oxc/crates/oxc_isolated_declarations/src/lib.rs

Lines 521 to 523 in 4608549

	let Some(TSModuleDeclarationBody::TSModuleBlock(block)) = &decl.body else {
	continue;
	};

Looks fishy! Shouldn't it walk down to find the nested TSModuleBlock when decl.body is a TSModuleDeclarationBody::TSModuleDeclaration?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Isolated declarations: Incorrect output for nested namespace #15729

---

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[codspeed-hq]

CodSpeed Performance Report

Merging #15800 will not alter performance

_{Comparing copilot/fix-namespace-declaration-output (51bc6c3) with main (e615162)¹}

Summary

✅ 38 untouched
⏩ 7 skipped²

Footnotes

1. No successful run was found on main (7f74c8a) during the generation of this report, so e615162 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Copilot]

Pull Request Overview

This PR fixes a variable shadowing bug in the isolated declarations transformer that caused dotted namespace syntax (export namespace X.Y.Z {}) to be incorrectly transformed. The namespace name was corrupted from the first identifier to the last identifier (e.g., X.Y.Z became Y.Z.Z).

Key changes:

• Renamed pattern match variable from decl to inner_decl in transform_ts_module_declaration to prevent shadowing the function parameter
• Added comprehensive test coverage for dotted namespace syntax with varying nesting depths (2, 3, and 4 levels)

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/oxc_isolated_declarations/src/declaration.rs	Fixed variable shadowing by renaming pattern match variable to inner_decl, preserving access to outer declaration's identifier
crates/oxc_isolated_declarations/tests/fixtures/nested-namespace-dotted.ts	Added test fixtures for dotted namespace syntax covering empty namespaces, namespaces with exports, and deeply nested structures
crates/oxc_isolated_declarations/tests/snapshots/nested-namespace-dotted.snap	Added snapshot expectations showing correct namespace name preservation in isolated declaration output

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[Dunqing]

Merge activity

• Nov 18, 3:38 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Nov 18, 3:38 AM UTC: Dunqing added this pull request to the Graphite merge queue.
• Nov 18, 3:44 AM UTC: Merged by the Graphite merge queue.