fix(scheduler): replace deprecated strings.Title with cases.Title

[mvanhorn]

Summary

Replace deprecated strings.Title() (deprecated since Go 1.18) with cases.Title(language.English).String() from golang.org/x/text in the scheduler metrics code.

Changes

• Created a package-level titleCaser variable using cases.Title(language.English) (safe for concurrent use)
• Replaced both strings.Title() calls in internal/scheduler/metrics.go
• Added imports for golang.org/x/text/cases and golang.org/x/text/language

Fixes #4776

This contribution was developed with AI assistance (Claude Code).

[greptile-apps]

Greptile Summary

This PR replaces the deprecated strings.Title() function (deprecated since Go 1.18) with cases.Title(language.English).String() from golang.org/x/text in the scheduler metrics code. Both call sites in updateClusterMetrics are updated inline, avoiding concurrency-safety concerns that would arise from sharing a cases.Caser instance across goroutines.

• Replaced strings.Title() at both call sites in internal/scheduler/metrics.go (lines 500 and 509)
• Uses cases.Title(language.English).String() directly at each call site (inlined, not a shared variable), addressing the previous reviewer concern about Caser thread safety
• golang.org/x/text is already a declared dependency (v0.33.0), so no go.mod changes are needed
• Minor: an extra blank line was inadvertently introduced after the import block (line 31)

Confidence Score: 5/5

Safe to merge — the fix is correct and complete, with only a trivial style nit remaining.

The deprecated strings.Title() calls are correctly replaced at both call sites. The previous concurrency concern (package-level Caser) was addressed by inlining the calls. The only remaining finding is a cosmetic extra blank line (P2), which does not affect correctness.

No files require special attention.

Important Files Changed

Filename	Overview
internal/scheduler/metrics.go	Replaces deprecated strings.Title() with cases.Title(language.English).String() inlined at both call sites; minor extra blank line introduced after import block

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["Phase string from protobuf\n(e.g. 'JOB_RUN_STATE_RUNNING')"] --> B["strings.ToLower()\n→ 'job_run_state_running'"]
    B --> C["cases.Title(language.English).String()\n→ 'Job_Run_State_Running'"]
    C --> D["Used as Prometheus metric label\n(phase field in key struct)"]

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[greptile-apps]

cases.Caser is not concurrency-safe — the comment is incorrect

The golang.org/x/text/cases package documentation explicitly states that a Caser "may be stateful and should therefore not be shared between goroutines." Only cases.Fold is documented as stateless; cases.Title, cases.Upper, and cases.Lower are all potentially stateful.

The comment here claims the opposite (concurrency-safe), which is incorrect. Because titleCaser is a package-level variable, any concurrent calls to titleCaser.String(...) — whether from multiple test goroutines or multiple MetricsCollector instances — constitute a data race.

The simplest safe fix is to remove the package-level variable entirely and call cases.Title(language.English).String(...) directly at each call site (lines 489 and 498). That removes any sharing concern altogether.

[dejanzele]

@mvanhorn can you adopt this suggestion?

[mvanhorn]

Done in dd1a072. Removed the package-level titleCaser and inlined cases.Title(language.English).String() at both call sites.