[linter-miner] Add slice-make-zero-length linter by github-actions[bot] · Pull Request #60310 · github/gh-aw

github-actions · 2026-09-11T17:47:31Z

Overview

This PR adds a new custom Go analysis linter: slice-make-zero-length

What the Linter Does

The linter reports make([]T, 0) calls without a capacity argument, which can lead to unnecessary allocations when the final slice length is known or can be estimated.

Example

// ❌ Bad - will reallocate as items are appended
result := make([]string, 0)
for _, item := range items {
    result = append(result, item)
}

// ✅ Good - pre-allocates capacity
result := make([]string, 0, len(items))
for _, item := range items {
    result = append(result, item)
}

Why This Matters

Performance: Pre-allocating capacity avoids repeated allocations and copies as slices grow
Code review: This is a common pattern suggestion in PR reviews
Idiomatic Go: Allocating with capacity is a best practice when the size is known

Evidence from Codebase

Found 10+ instances in the repository where make([]T, 0) is used:

pkg/github/label_objective_mapping.go:203
pkg/workflow/checkout_manager.go:590
pkg/workflow/enclaves.go:116
pkg/workflow/workflow_errors.go:204
pkg/cli/bootstrap_shared.go:27
pkg/cli/graders_operational_value_report_history.go:49
pkg/cli/deploy_command.go:297
And more...

Implementation

New files: pkg/linters/slicemakezerolength/ (analyzer, tests, fixtures)
Modified files: pkg/linters/registry.go (registration)
Test coverage: 4 bad cases + 5 good cases verified
Build verification: Compiles successfully, all tests pass

Validation

✅ All linter tests pass
✅ Linter compiles without errors
✅ Registered in custom linter suite
✅ make golint-custom runs successfully

Warning

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Generated by Linter Miner · copilot · mai10 · 108.6 AIC · ⊞ 6.9K · ◷

expires on Sep 18, 2026, 9:47 AM UTC-08:00

This linter reports make([]T, 0) calls without a capacity argument, which can lead to unnecessary allocations when the final slice length is known. Providing a capacity upfront reduces the number of allocations and improves performance. Example: result := make([]string, 0) // bad - will reallocate as items added for _, item := range items { result = append(result, item) } result := make([]string, 0, len(items)) // good - pre-allocates The linter detects patterns where make([]T, 0) is used on slices and suggests providing capacity, helping improve the efficiency of code that builds slices incrementally. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-09-11T18:07:05Z

✅ Ponytail Reviewer completed successfully!

Lean already. Ship.

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Generated by Ponytail Reviewer for #60310

github-actions · 2026-09-11T18:07:20Z

⚠️ PR Code Quality Reviewer failed during code quality review.

Warning

Threat Detection Engine Failure — The analysis engine could not complete. This is a tooling failure, not a security finding.

What happened

The threat detection engine failed to produce results.

Review the workflow run logs for details.

🔎 Code quality review by PR Code Quality Reviewer

github-actions · 2026-09-11T18:07:41Z

✅ Test Quality Sentinel completed test quality analysis.

Test Quality Sentinel skipped because pre-fetch PR data was unavailable: unable to fetch test file diff

🧪 Test quality analysis by Test Quality Sentinel

github-actions · 2026-09-11T18:07:41Z

⚠️ Security scanning failed for Design Decision Gate 🏗️. Review the logs for details.

🏗️ ADR gate enforced by Design Decision Gate 🏗️

github-actions · 2026-09-11T18:07:44Z

🧠 Matt Pocock Skills Reviewer has completed the skills-based review. ✅

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🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer

github-actions · 2026-09-11T18:12:23Z

🏗️ ADR required for PR #60310

I generated a draft ADR and pushed it to this PR branch:

docs/adr/60310-add-slice-make-zero-length-linter.md

Evidence used

ADR enforcement is required because this PR adds 187 lines in business-logic directories and exceeds the default 100-line threshold.
The PR adds a new analyzer at pkg/linters/slicemakezerolength/slicemakezerolength.go and registers it in pkg/linters/registry.go.
No existing ADR was referenced in the PR body, and the most recent ADRs on the branch do not cover this new linter decision.

Inferred design decision

Add a repository-wide custom linter that flags make([]T, 0) without an explicit capacity.
Codify a repeated performance/code-review recommendation as automated static analysis.

Next action

Please review and refine the draft ADR, especially the decision scope and trade-offs, before treating this PR as ADR-backed.

🏗️ ADR gate enforced by Design Decision Gate 🏗️ · pi · gpt54 · 14.7 AIC · ⊞ 10.1K · ◷
_{Comment /review to run again}

Copilot

🟡 Changes recommended

The analyzer produces false positives and its registration leaves required documentation, tests, CI configuration, and existing findings unresolved.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds a custom Go analyzer intended to detect zero-length slice allocations without capacity hints.

Changes:

Implements and registers slicemakezerolength.
Adds coverage and nolint handling.
Adds analyzer fixtures and tests.

File summaries

File	Description
`pkg/linters/slicemakezerolength/slicemakezerolength.go`	Implements analyzer logic.
`pkg/linters/slicemakezerolength/slicemakezerolength_test.go`	Runs analyzer tests.
`pkg/linters/slicemakezerolength/testdata/src/slicemakezerolength/slicemakezerolength.go`	Provides test fixtures.
`pkg/linters/registry.go`	Registers the analyzer.

Review details

Suppressed comments (1)

pkg/linters/registry.go:129

Adding this analyzer to linters.All() without updating the synchronized surfaces makes the existing linter tests fail. doc_sync_test.go:97-107 requires matching entries in doc.go, the README Subpackages table, and spec_test.go's documentedAnalyzers; lines 129-136 also require the analyzer in both cgo.yml flag sets or in notYetEnforced. Please update those surfaces together with this registration.

	slicemakezerolength.Analyzer,

Files reviewed: 5/5 changed files
Comments generated: 2
Review effort level: Balanced

💡 Add a code-review agent skill for context-aware, tailored reviews. Learn more in the docs.

Copilot · 2026-09-11T19:21:31Z

 	regexpdynamicpattern.Analyzer,
 	ssljson.Analyzer,
 	seenmapbool.Analyzer,
+	slicemakezerolength.Analyzer,


Addressed in 9ca42be. The analyzer now reports only an immediately following known-size range loop that appends exactly one element per iteration, and its isolated repository-wide run passes without findings.

Copilot · 2026-09-11T19:21:31Z

+	// The second argument must be a literal 0.
+	if !isZeroLiteral(call.Args[1]) {
+		return


Addressed in 9ca42be. No-growth, conditional-growth, channel-range, multi-append, and self-range cases are now excluded; fixtures cover each case.

github-actions

Skills-Based Review 🧠

Applied /codebase-design and /tdd — requesting changes: the new analyzer isn't registered in the repo's enforced documentation surface, which breaks CI.

📋 Key Themes & Highlights

Key Themes

Blocking: pkg/linters/registry.go registers slicemakezerolength.Analyzer in allAnalyzers, but pkg/linters/README.md was not updated (Overview bullets + Public API table). I ran the existing doc-sync tests locally and confirmed TestRegistryMatchesDocumentation and TestDocSurfacesMatchRegistryAndSpecList fail on this branch ("...should have 68 item(s), but has 69"). This will fail CI as-is.
Minor: isZeroLiteral compares literal text against "0" only, missing equivalent zero forms (0x0, 0_0, 00). Low real-world impact, but a small correctness gap worth a follow-up test.

Positive Highlights

✅ Correctly follows the coverage-aware perf-gating pattern (RegisterHotThresholdFlag + coverage.ShouldApply) used by other allocation-related linters like seenmapbool/mapclearloop.
✅ Good nolint directive support and generated-file skip via filecheck.ShouldSkipFilename.
✅ Test fixtures cover both flagged and suppressed cases (capacity given, length given, array types, nolint).

@copilot please address the review comments above.

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🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer · copilot · sonnet50 · 55.9 AIC · ⌖ 16.1 AIC · ⊞ 10.4K
_{Comment /matt to run again}

github-actions · 2026-09-11T18:15:43Z

 	regexpdynamicpattern.Analyzer,
 	ssljson.Analyzer,
 	seenmapbool.Analyzer,
+	slicemakezerolength.Analyzer,


[/codebase-design] This PR registers slicemakezerolength in allAnalyzers but does not add the corresponding entry to pkg/linters/README.md (Overview bullet list + Public API table). The repo enforces this with TestRegistryMatchesDocumentation / TestDocSurfacesMatchRegistryAndSpecList in pkg/linters/spec_test.go and doc_sync_test.go, and I confirmed both fail against this branch (68 item(s), but has 69).

💡 Fix

Add a bullet to the Overview list and a row to the Public API table in pkg/linters/README.md, alphabetically placed near seenmapbool/sortslice, e.g.:

- `slicemakezerolength` — reports `make([]T, 0)` calls without a capacity argument when the final slice length is known, which can be optimized.

And in the Public API table:

| `slicemakezerolength` | Custom `go/analysis` analyzer that flags `make([]T, 0)` calls without capacity when the final length is known |

Also consider whether this should be added to the coverage-gated linter list in the README (it registers a -hot-threshold flag consistent with other perf linters like mapclearloop/seenmapbool, so it belongs in that enumerated list too).

@copilot please address this.

Addressed in 9ca42be. README.md, doc.go, spec_test.go, and both native/wasm CI linter flag sets now include slicemakezerolength; synchronization tests pass.

github-actions · 2026-09-11T18:15:44Z

+// isZeroLiteral reports whether expr is the literal 0.
+func isZeroLiteral(expr ast.Expr) bool {
+	lit, ok := expr.(*ast.BasicLit)
+	if !ok {


[/tdd] isZeroLiteral only matches the exact literal text "0", so equivalent zero literals like 0x0, 0_0, or 00 silently bypass the check — a minor false-negative gap, not a blocker.

💡 Suggested test + fix

Parse the literal value instead of comparing raw text, e.g. using strconv.ParseInt(lit.Value, 0, 64) and checking == 0, or go/constant.MakeFromLiteral for correctness across bases/underscores. Add a fixture case:

func badZeroLengthHex() { s := make([]int, 0x0) // want `make\(\[\]int, 0x0\) without capacity can be optimized` _ = s }

Low impact since 0x0/0_0 are rare in practice, but worth tightening if this linter graduates into the coverage-gated hot-path set where correctness matters more.

@copilot please address this.

Addressed in 9ca42be. Zero detection now uses go/constant, with a 0x0 regression fixture.

pelikhan · 2026-09-11T19:00:26Z

@copilot run pr-finisher skill

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-09-11T19:21:31Z

@copilot run pr-finisher skill

Ran the pr-finisher workflow and pushed 9ca42be. Review feedback is addressed; formatting, lint, full tests, workflow recompilation, secret scanning, and final security validation pass locally. CI must be re-triggered by a maintainer for the new HEAD.

github-actions · 2026-09-12T00:01:23Z

🎉 This pull request is included in a new release.

Release: v0.89.7

github-actions Bot added automation cookie Issue Monster Loves Cookies! go-linters labels Sep 11, 2026

github-actions Bot mentioned this pull request Sep 11, 2026

[WIP] Linter Miner: work in progress #60307

Closed

pelikhan marked this pull request as ready for review September 11, 2026 18:05

Copilot AI balanced review requested due to automatic review settings September 11, 2026 18:05

Copilot started reviewing on behalf of pelikhan September 11, 2026 18:06 View session

Add ADR for slice-make-zero-length linter

f80cc6b

github-actions Bot added the needs-review label Sep 11, 2026

Copilot AI reviewed Sep 11, 2026

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github-actions Bot commented Sep 11, 2026

View reviewed changes

Copilot started work on behalf of pelikhan September 11, 2026 19:01 View session

Copilot AI and others added 2 commits September 11, 2026 19:04

Start PR readiness review

fd312cb

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Fix slice capacity linter precision and integration

9ca42be

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot finished work on behalf of pelikhan September 11, 2026 19:22

Copilot AI requested a review from pelikhan September 11, 2026 19:22

pelikhan merged commit f89909d into main Sep 11, 2026

pelikhan deleted the linter-miner/slice-make-zero-length-5440d9de2a50e456 branch September 11, 2026 19:32

This was referenced Sep 12, 2026

slicemakezerolength (69th linter): make()-only scope misses the more idiomatic var s []T nil-slice pattern #60367

Closed

[instructions] Sync instruction files with recent safe-output and CLI changes #60603

Merged

github-actions Bot mentioned this pull request Sep 13, 2026

[instructions] Sync instruction files with recent safe-output and CLI changes #60604

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github-actions Bot commented Sep 11, 2026

Overview

What the Linter Does

Example

Why This Matters

Evidence from Codebase

Implementation

Validation

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