perf: fix FindIncludesInContent regression (+33.8%) by eliminating regex allocations by Copilot · Pull Request #28865 · github/gh-aw

Copilot · 2026-04-28T06:25:57Z

findIncludesInContent called parser.ParseImportDirective per line, which runs a complex alternation regex via FindStringSubmatch — allocating a submatch []string, backtracking state, and an ImportDirectiveMatch struct on every directive hit. This caused 18 allocs/op and was the source of the reported regression.

Changes

pkg/cli/remove_command.go: Replace ParseImportDirective with a new parseIncludePath helper that uses strings.HasPrefix + strings.Cut + strings.TrimSpace instead of regex. Handles all three directive forms: @include, @import, {{#import}}.
Correctness fix in {{#import}} colon handling: Explicit single-colon removal to match the original regex's \s*:?\s* semantics.
Correctness fix in {{#import}} trailing content: Validates that text after }} is empty/whitespace, rejecting lines like {{#import shared/x.md}} trailing (matching the original anchored regex's behavior).
Tests: Added 8 new test cases covering @import (basic, optional marker, section reference) and all {{#import}} variants (colon, no-colon, optional marker, section reference, trailing-content rejection).
Removed now-unused parser import.

Benchmark (AMD EPYC 7763)

	ns/op	B/op	allocs/op
Before	2109	840	18
After	265	112	3
Δ	~8× faster	~7.5× less	6× fewer

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/e0d1eeba-1e83-4b71-9ad8-7d48cbdb4d2a Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>

…rect string ops Replace parser.ParseImportDirective (regex + struct allocs) in findIncludesInContent with inline parseIncludePath helper using strings.HasPrefix/Cut/TrimSpace. Benchmark (AMD EPYC 7763): Before: 2109 ns/op 840 B/op 18 allocs/op After: 265 ns/op 112 B/op 3 allocs/op (~8x faster, 6x fewer allocs) Agent-Logs-Url: https://github.com/github/gh-aw/sessions/e0d1eeba-1e83-4b71-9ad8-7d48cbdb4d2a Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>

Copilot

Pull request overview

Improves performance of include scanning in findIncludesInContent by replacing regex-based import directive parsing with a zero/low-allocation string parser, addressing a reported regression.

Changes:

Replaced parser.ParseImportDirective usage in findIncludesInContent with a new parseIncludePath helper using HasPrefix/Cut/TrimSpace.
Added pull-requests: write to the activation job permissions in several *.lock.yml workflows.
Removed now-unused parser import from pkg/cli/remove_command.go.

Show a summary per file

File	Description
pkg/cli/remove_command.go	Introduces `parseIncludePath` and switches include scanning to use it instead of the regex-based parser.
.github/workflows/unbloat-docs.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/tidy.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/plan.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/pdf-summary.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/mergefest.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/brave.lock.yml	Adds `pull-requests: write` permission to the activation job.
.github/workflows/ace-editor.lock.yml	Adds `pull-requests: write` permission to the activation job.

Copilot's findings

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Comments suppressed due to low confidence (1)

.github/workflows/tidy.lock.yml:95

This PR’s title/description focuses on the Go perf regression in FindIncludesInContent, but it also changes workflow token permissions by adding pull-requests: write here (and in other lock workflows). If this is intentional, please update the PR description to explain why these permission changes are needed (or consider splitting them into a separate PR).

      actions: read
      contents: read
      issues: write
      pull-requests: write

Files reviewed: 8/8 changed files
Comments generated: 9

Copilot · 2026-04-28T09:18:36Z

+		// Extract path up to closing "}}"
+		before, _, ok := strings.Cut(rest, "}}")
+		if !ok {


For the {{#import}} form, this parses everything up to the first "}}" but does not verify that the closing braces are at the end of the directive (the previous anchored regex required the line to end at "}}" apart from whitespace). As a result, a line like "{{#import shared/x.md}} trailing" would now be treated as a directive and produce a false include. Consider validating that the text after the cut is empty/whitespace (e.g., capture the remainder from strings.Cut and require strings.TrimSpace(remainder)=="") before returning a path.

Suggested change

// Extract path up to closing "}}"

before, _, ok := strings.Cut(rest, "}}")

if !ok {

// Extract path up to closing "}}" and require only whitespace after it.

before, after, ok := strings.Cut(rest, "}}")

if !ok || strings.TrimSpace(after) != "" {

Copilot · 2026-04-28T09:18:37Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

This issue also appears on line 92 of the same file.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:37Z

      contents: read
      discussions: write
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:37Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:38Z

+// parseIncludePath extracts the file path from @include/@import/{{#import}} directive lines
+// without allocating a regex submatch slice or a directive struct.
+// Returns an empty string if the line is not a recognised directive.
+// Section references (e.g. file.md#Section) are stripped from the returned path.
+func parseIncludePath(line string) string {


This new parsing logic supports @import and {{#import}} (with optional '?' and optional ':'), but the existing findIncludesInContent tests only cover @include. Please add unit tests that exercise @import and the {{#import}} variants (colon/no-colon and optional marker) to ensure behavior stays aligned with the legacy regex-based parser.

Copilot · 2026-04-28T09:18:38Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:38Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:39Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

Copilot · 2026-04-28T09:18:39Z

      actions: read
      contents: read
      issues: write
+      pull-requests: write


Adding pull-requests: write increases the GITHUB_TOKEN scope for this job. The activation job’s “Add comment with workflow run link” script posts via the issues comments endpoint (/repos/{owner}/{repo}/issues/{number}/comments in actions/setup/js/add_workflow_run_comment.cjs), which only requires issues: write. Unless another step in this job truly needs PR write access, please drop pull-requests: write to follow least-privilege permissions.

Suggested change

pull-requests: write

…sion

github-actions · 2026-04-28T09:24:42Z

🛠️ Agentic Maintenance updated this pull request branch.

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pelikhan · 2026-04-28T09:26:48Z

@copilot review all comments

…t}} trailing content, add tests - Revert unintended pull-requests:write additions to 7 lock files - Fix {{#import}} parser to reject directives with trailing content after }} - Add test cases for @import and {{#import}} directive variants Agent-Logs-Url: https://github.com/github/gh-aw/sessions/042e8ccf-a206-4fd4-8347-dcf4020b615f Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-04-28T09:33:23Z

@copilot review all comments

Addressed all comments in commit 482efaa:

{{#import}} trailing content (line 434-436): fixed to capture and validate the remainder after }}, rejecting lines like {{#import shared/x.md}} trailing.
Missing tests (lines 405-409): added 8 new test cases covering @import basic, optional marker, section reference, and all {{#import}} variants (colon, no-colon, optional marker, section reference, and trailing-content rejection).
pull-requests: write in lock files: reverted the unintended additions to all 7 affected .lock.yml files.

…sion

github-actions · 2026-04-28T09:35:05Z

🛠️ Agentic Maintenance updated this pull request branch.

View workflow run

Initial plan

89eccd4

Copilot AI assigned Copilot and gh-aw-bot Apr 28, 2026

Copilot started work on behalf of gh-aw-bot April 28, 2026 06:26 View session

Copilot AI linked an issue Apr 28, 2026 that may be closed by this pull request

[performance] Regression in FindIncludesInContent: +33.8% slower #28864

Closed

Copilot AI and others added 2 commits April 28, 2026 06:34

perf: initial analysis - no changes yet

1a12263

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/e0d1eeba-1e83-4b71-9ad8-7d48cbdb4d2a Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix performance regression in FindIncludesInContent~~ perf: fix FindIncludesInContent regression (+33.8%) by eliminating regex allocations Apr 28, 2026

Copilot AI requested a review from gh-aw-bot April 28, 2026 06:45

Copilot finished work on behalf of gh-aw-bot April 28, 2026 06:45

github-actions Bot mentioned this pull request Apr 28, 2026

[aw] No-Op Runs #28859

Closed

pelikhan marked this pull request as ready for review April 28, 2026 09:10

Copilot AI review requested due to automatic review settings April 28, 2026 09:10

Copilot started reviewing on behalf of pelikhan April 28, 2026 09:11 View session

Copilot AI reviewed Apr 28, 2026

View reviewed changes

Merge branch 'main' into copilot/performance-fix-find-includes-regres…

3f060bb

…sion

github-actions Bot mentioned this pull request Apr 28, 2026

Smoke Test: Claude - 25044466924 #28886

Closed

Copilot started work on behalf of pelikhan April 28, 2026 09:26 View session

Copilot finished work on behalf of pelikhan April 28, 2026 09:35

Merge branch 'main' into copilot/performance-fix-find-includes-regres…

78b3226

…sion

Copilot AI requested a review from pelikhan April 28, 2026 09:35

pelikhan merged commit 49d5bc6 into main Apr 28, 2026

pelikhan deleted the copilot/performance-fix-find-includes-regression branch April 28, 2026 09:37

github-actions Bot mentioned this pull request Apr 28, 2026

[Contribution Check Report] Contribution Check — 2026-04-28 #28835

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Copilot AI commented Apr 28, 2026 •

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