fix(transformer/tagged-template-transform): handle `\n` escape sequences #15830

Dunqing · 2025-11-18T08:35:59Z

Fixes the issue identified in #15664 where the tagged template transform plugin incorrectly handled template literals containing escape sequences.

Examples

// Input
foo`</script>\n`
// Before (incorrect): 
foo(_t || (_t = taggedTemplateLiteral(["</script>\\n"])));
// After (correct):
foo(_t || (_t = taggedTemplateLiteral(["</script>\n"], ["</script>\\n"])));

// Input with invalid escape
foo`</script>\u`
// Before (syntax error):
foo(_t || (_t = taggedTemplateLiteral(["</script>\\u"])));
// After (correct):
foo(_t || (_t = taggedTemplateLiteral([void 0], ["</script>\\u"])));

Dunqing · 2025-11-18T08:36:17Z

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codspeed-hq · 2025-11-18T08:40:22Z

CodSpeed Performance Report

Merging #15830 will not alter performance

_{Comparing 11-18-fix_transformer_handle_escape_sequences_in_tagged_template_transform (d973355) with main (2191ae9)}

Summary

✅ 38 untouched
⏩ 7 skipped¹

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 the handling of escape sequences in the tagged template transform plugin. Previously, the plugin incorrectly transformed template literals containing escape sequences (like \n, \t) or invalid escape sequences (like incomplete \u), causing either incorrect output or syntax errors.

The key changes include:

Modified the transform to generate both "cooked" and "raw" string arrays when they differ
Added support for invalid escape sequences using void 0 in the cooked array
Added comprehensive test coverage for both valid and invalid escape sequences

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`crates/oxc_transformer/src/plugins/tagged_template_transform.rs`	Updated transform logic to detect when cooked differs from raw, generate both cooked and raw arrays when needed, and use `void 0` for invalid escapes
`tasks/transform_conformance/tests/plugin-tagged-template-transform/test/fixtures/escape-sequence/input.js`	Added test input for valid escape sequences (`\n` and `\t`)
`tasks/transform_conformance/tests/plugin-tagged-template-transform/test/fixtures/escape-sequence/output.js`	Added expected output showing correct handling of escape sequences with dual array arguments
`tasks/transform_conformance/tests/plugin-tagged-template-transform/test/fixtures/invalid-escape/input.js`	Added test input for invalid escape sequence (`\u`)
`tasks/transform_conformance/tests/plugin-tagged-template-transform/test/fixtures/invalid-escape/output.js`	Added expected output showing `void 0` in cooked array for invalid escape
`tasks/transform_conformance/snapshots/oxc.snap.md`	Updated test pass count from 198/329 to 200/331, reflecting the 2 new passing tests

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overlookmotel

Looks good!

overlookmotel · 2025-11-19T23:36:01Z

Merge activity

Nov 19, 11:36 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Nov 19, 11:36 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Nov 19, 11:41 PM UTC: Merged by the Graphite merge queue.

…ces (#15830) Fixes the issue identified in #15664 where the tagged template transform plugin incorrectly handled template literals containing escape sequences. ### Examples ```js // Input foo`</script>\n` // Before (incorrect): foo(_t || (_t = taggedTemplateLiteral(["</script>\\n"]))); // After (correct): foo(_t || (_t = taggedTemplateLiteral(["</script>\n"], ["</script>\\n"]))); // Input with invalid escape foo`</script>\u` // Before (syntax error): foo(_t || (_t = taggedTemplateLiteral(["</script>\\u"]))); // After (correct): foo(_t || (_t = taggedTemplateLiteral([void 0], ["</script>\\u"])));

@license

### 💥 BREAKING CHANGES - cbb27fd ast: [**BREAKING**] Add `TSGlobalDeclaration` type (#15712) (overlookmotel) ### 🚀 Features - 0c1f82b linter/plugins: Add `tokens` property to `Program` (#16020) (overlookmotel) - 6cff132 span: Add `Span::merge_within` method (#15869) (sapphi-red) - 102365d allocator/vec: Add `Vec::into_bump_slice` method (#15770) (Dunqing) ### 🐛 Bug Fixes - e2ca770 codegen: Add support for printing type arguments in new expressions (#15963) (Ives van Hoorne) - 2bd3cb6 apps, editors, napi: Fix `oxlint-disable` comments (#16014) (overlookmotel) - 622cb5e parser: Preserve legal comments with @preserve/@license when preceded by other annotations (#15929) (copilot-swe-agent) - 7c46a9e transformer/tagged-template-transform: Handle `\n` escape sequences (#15830) (Dunqing) - f386efc minifier: Avoid generating invalid spans (#15778) (sapphi-red) - d4ff004 parser: Forbid invalid modifiers on `module` and `global` (#15723) (overlookmotel) - 2191ae9 semantic: Allow reserved keywords in typescript ambient contexts (#15495) (sapphi-red) - 7d1ebad isolated-declarations: Incorrect nested namespace output in isolated declarations (#15800) (copilot-swe-agent) ### ⚡ Performance - b4b0ed8 transformer/typescript: Reverse order of checks (#15722) (overlookmotel) ### 📚 Documentation - c81a331 data_structures: Doc comments on fields of `Stack` (#15793) (overlookmotel) - cfae31d allocator: Use `allocator` as var name in examples (#15781) (overlookmotel) Co-authored-by: Boshen <[email protected]>

github-actions bot added A-transformer Area - Transformer / Transpiler C-bug Category - Bug labels Nov 18, 2025

Dunqing changed the title ~~fix(transformer): handle escape sequences in tagged template transform~~ fix(transformer/tagged-template-transform): handle escape sequences Nov 18, 2025

Dunqing changed the title ~~fix(transformer/tagged-template-transform): handle escape sequences~~ fix(transformer/tagged-template-transform): handle \n escape sequences Nov 18, 2025

Dunqing force-pushed the 11-18-fix_transformer_handle_escape_sequences_in_tagged_template_transform branch from 603308c to d973355 Compare November 18, 2025 08:44

Dunqing mentioned this pull request Nov 18, 2025

perf(transformer/tagged-template-transform): improve performance #15834

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Dunqing marked this pull request as ready for review November 18, 2025 12:31

Dunqing requested a review from overlookmotel as a code owner November 18, 2025 12:31

Copilot AI review requested due to automatic review settings November 18, 2025 12:31

Copilot started reviewing on behalf of Dunqing November 18, 2025 12:31 View session

Copilot finished reviewing on behalf of Dunqing November 18, 2025 12:33

Copilot AI reviewed Nov 18, 2025

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overlookmotel approved these changes Nov 19, 2025

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overlookmotel added the 0-merge Merge with Graphite Merge Queue label Nov 19, 2025

graphite-app bot force-pushed the 11-18-fix_transformer_handle_escape_sequences_in_tagged_template_transform branch from d973355 to 7c46a9e Compare November 19, 2025 23:36

graphite-app bot merged commit 7c46a9e into main Nov 19, 2025
20 checks passed

graphite-app bot deleted the 11-18-fix_transformer_handle_escape_sequences_in_tagged_template_transform branch November 19, 2025 23:41

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Nov 19, 2025

Boshen mentioned this pull request Nov 24, 2025

release(crates): oxc v0.99.0 #16037

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Merging #15830 will not alter performance

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fix(transformer/tagged-template-transform): handle `\n` escape sequences #15830

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