feat(regular_expression): improve error messages by sapphi-red · Pull Request #16953 · oxc-project/oxc

sapphi-red · 2025-12-16T11:19:43Z

Improved error messages for regex parse failures.

sapphi-red · 2025-12-16T11:20:05Z

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codspeed-hq · 2025-12-16T11:25:06Z

CodSpeed Performance Report

Merging #16953 will not alter performance

_{Comparing 12-16-feat_regular_expression_improve_error_messages (6e13eda) with main (3c39d46)}

Summary

✅ 42 untouched
⏩ 3 skipped¹

3 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 enhances error messages for regular expression parsing failures by adding helpful, actionable guidance to diagnostic messages. The changes improve developer experience by providing specific suggestions for fixing regex errors, such as explaining valid flags, suggesting fixes for common mistakes, and showing available group names for invalid references.

Key changes:

Added help messages to all regex parser diagnostics with specific, actionable guidance
Enhanced reference error messages to show available groups/names
Improved error specificity by splitting generic errors into more targeted ones (e.g., duplicated vs invalid modifiers)

Reviewed changes

Copilot reviewed 7 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`crates/oxc_regular_expression/src/diagnostics.rs`	Added help messages to all diagnostic functions with actionable guidance for fixing regex errors
`crates/oxc_regular_expression/src/parser/pattern_parser/pattern_parser_impl.rs`	Updated to pass context (group counts, available names) to diagnostics for better error messages
`crates/oxc_regular_expression/src/parser/flags_parser.rs`	Exported constants for valid flags and modifiers to use in help messages
`crates/oxc_regular_expression/src/parser/mod.rs`	Re-exported flags/modifiers constants for use in diagnostics
`crates/oxc_regular_expression/tests/diagnostics.rs`	Added test cases for new error scenarios with better context
Snapshot files	Updated to reflect new help messages in diagnostic output

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leaysgur

Good work as always. 🕺🏻

I have 2 points:

Want to keep diagnostics() a pure function
- Pass VALID_XXX as an argument only where necessary
Use VALID_XXX in the implementation as well
- Some code changes might be needed, but I want to avoid double definitions

Does it make sense?

sapphi-red · 2025-12-17T08:23:10Z

Would you elaborate what you mean by diagnostics()?

leaysgur · 2025-12-17T08:45:41Z

use xxx::VALID_FLAGS;

#[cold]
pub fn unknown_flag(span: Span, flag: &str) -> OxcDiagnostic {
    OxcDiagnostic::error(format!("{PREFIX} Unknown flag: `{flag}` found"))
        .with_label(span)
        .with_help(format!("Valid flags are: {}", VALID_FLAGS.join(", ")))
}

⬇️

#[cold]
pub fn unknown_flag(span: Span, flag: &str, valid_flags) -> OxcDiagnostic {
    OxcDiagnostic::error(format!("{PREFIX} Unknown flag: `{flag}` found"))
        .with_label(span)
        .with_help(format!("Valid flags are: {}", valid_flags.join(", ")))
}

However, this is nits. 😅

sapphi-red · 2025-12-17T09:00:34Z

Ah, I see.

leaysgur

🙏🏻

crates/oxc_regular_expression/src/parser/flags_parser.rs

crates/oxc_regular_expression/src/parser/pattern_parser/pattern_parser_impl.rs

leaysgur

Thank you~! 🎅🏻

leaysgur · 2025-12-19T02:21:39Z

Merge activity

Dec 19, 2:21 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Dec 19, 2:21 AM UTC: leaysgur added this pull request to the Graphite merge queue.
Dec 19, 2:25 AM UTC: leaysgur removed this pull request from the Graphite merge queue.
Dec 19, 3:26 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Dec 19, 3:26 AM UTC: leaysgur added this pull request to the Graphite merge queue.
Dec 19, 3:26 AM UTC: Merged by the Graphite merge queue.

Improved error messages for regex parse failures.

leaysgur · 2025-12-19T02:26:55Z

I've just noticed that our release flow is now running.

I'll add the merge label again once the release has finished.

github-actions bot added the C-enhancement Category - New feature or request label Dec 16, 2025

sapphi-red mentioned this pull request Dec 16, 2025

fix(regular_expression): correct named capture group reference error #16952

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sapphi-red changed the base branch from 12-16-fix_regular_expression_correct_named_capture_group_reference_error to graphite-base/16953 December 16, 2025 11:29

sapphi-red force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 29407b9 to c70e2c8 Compare December 16, 2025 11:38

sapphi-red force-pushed the graphite-base/16953 branch from 966eea2 to 6d2d18c Compare December 16, 2025 11:38

sapphi-red changed the base branch from graphite-base/16953 to 12-16-fix_regular_expression_correct_named_capture_group_reference_error December 16, 2025 11:38

github-actions bot added the A-linter Area - Linter label Dec 16, 2025

graphite-app bot force-pushed the 12-16-fix_regular_expression_correct_named_capture_group_reference_error branch from 6d2d18c to b068bbf Compare December 16, 2025 11:39

graphite-app bot force-pushed the 12-16-feat_regular_expression_improve_error_messages branch 2 times, most recently from 51f0fa2 to 10bef7f Compare December 16, 2025 11:40

sapphi-red force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 10bef7f to 6ba13c3 Compare December 16, 2025 12:09

sapphi-red force-pushed the 12-16-fix_regular_expression_correct_named_capture_group_reference_error branch from b068bbf to bac65ed Compare December 16, 2025 12:09

graphite-app bot changed the base branch from 12-16-fix_regular_expression_correct_named_capture_group_reference_error to graphite-base/16953 December 17, 2025 00:38

graphite-app bot force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 6ba13c3 to 6642764 Compare December 17, 2025 00:46

graphite-app bot force-pushed the graphite-base/16953 branch from bac65ed to 5a2af88 Compare December 17, 2025 00:46

graphite-app bot changed the base branch from graphite-base/16953 to main December 17, 2025 00:46

graphite-app bot force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 6642764 to b6368a6 Compare December 17, 2025 00:47

sapphi-red force-pushed the 12-16-feat_regular_expression_improve_error_messages branch 2 times, most recently from 2b94d9e to 9d8630a Compare December 17, 2025 07:39

sapphi-red assigned leaysgur Dec 17, 2025

sapphi-red marked this pull request as ready for review December 17, 2025 07:48

sapphi-red requested review from camc314 and leaysgur as code owners December 17, 2025 07:48

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sapphi-red force-pushed the 12-16-feat_regular_expression_improve_error_messages branch 2 times, most recently from ea162dd to 3804102 Compare December 17, 2025 09:10

sapphi-red requested a review from leaysgur December 18, 2025 13:06

leaysgur requested changes Dec 19, 2025

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crates/oxc_regular_expression/src/parser/flags_parser.rs Show resolved Hide resolved

crates/oxc_regular_expression/src/parser/pattern_parser/pattern_parser_impl.rs Outdated Show resolved Hide resolved

sapphi-red force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 3804102 to 6e13eda Compare December 19, 2025 02:00

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leaysgur added the 0-merge Merge with Graphite Merge Queue label Dec 19, 2025

feat(regular_expression): improve error messages (#16953)

3e2ae7b

Improved error messages for regex parse failures.

graphite-app bot force-pushed the 12-16-feat_regular_expression_improve_error_messages branch from 6e13eda to 3e2ae7b Compare December 19, 2025 02:22

leaysgur removed the 0-merge Merge with Graphite Merge Queue label Dec 19, 2025

leaysgur added the 0-merge Merge with Graphite Merge Queue label Dec 19, 2025

graphite-app bot merged commit 3e2ae7b into main Dec 19, 2025
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graphite-app bot deleted the 12-16-feat_regular_expression_improve_error_messages branch December 19, 2025 03:26

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

This was referenced Dec 22, 2025

release(crates): oxc v0.105.0 #17259

Merged

release(apps): oxlint v1.35.0 && oxfmt v0.20.0 #17260

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