[rust-guard] Rust Guard: Redundant match arms & duplicate integrity-branch logic

[github-actions]

🦀 Rust Guard Improvement Report

Improvement 1: Redundant match arm in author_association_floor_from_str

Category: Dead Code
File(s): guards/github-guard/rust-guard/src/labels/helpers.rs
Effort: Small (< 15 min)
Risk: Low

Problem

Lines 907–908 contain two consecutive match arms that both return vec![]. The "FIRST_TIMER" | "NONE" arm is entirely subsumed by the wildcard _ arm — it is dead code, never distinguished from the catch-all:

// helpers.rs line 904
match normalized.as_str() {
    "OWNER" | "MEMBER" | "COLLABORATOR" => writer_integrity(scope, ctx),
    "CONTRIBUTOR" | "FIRST_TIME_CONTRIBUTOR" => reader_integrity(scope, ctx),
    "FIRST_TIMER" | "NONE" => vec![],  // ← identical to the arm below
    _ => vec![],                        // ← wildcard already covers these
}

The doc comment already documents the intended mapping, so the explicit arms add no informational value over a single wildcard.

Suggested Change

Remove the "FIRST_TIMER" | "NONE" arm and consolidate the no-op cases into the wildcard:

Before

match normalized.as_str() {
    "OWNER" | "MEMBER" | "COLLABORATOR" => writer_integrity(scope, ctx),
    "CONTRIBUTOR" | "FIRST_TIME_CONTRIBUTOR" => reader_integrity(scope, ctx),
    "FIRST_TIMER" | "NONE" => vec![],
    _ => vec![],
}

After

match normalized.as_str() {
    "OWNER" | "MEMBER" | "COLLABORATOR" => writer_integrity(scope, ctx),
    "CONTRIBUTOR" | "FIRST_TIME_CONTRIBUTOR" => reader_integrity(scope, ctx),
    _ => vec![], // FIRST_TIMER, NONE, or any unrecognised value
}

Why This Matters

Dead match arms are misleading — a reader may wonder whether "FIRST_TIMER" and "NONE" are intended to be treated differently from unknown values. Removing them signals clearly that all remaining cases are equivalent, and the doc comment already documents the intended semantics. Rust's exhaustive match means no behaviour change whatsoever.

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Improvement 2: Duplicate integrity-assignment branches in label_resource

Category: Code Duplication
File(s): guards/github-guard/rust-guard/src/lib.rs
Effort: Small (< 15 min)
Risk: Low

Problem

Lines 620–641 contain three separate if !repo_id.is_empty() guards with duplicated assignment bodies inside the is_write_operation block:

1. is_merge_operation → writer_integrity (lines 622–626)
2. is_delete_operation → writer_integrity (lines 627–631) ← identical body to case 1
3. is_update_operation || is_create_operation → reader_integrity (lines 632–638)
4. final else → reader_integrity (lines 639–641) ← identical body to case 3

if tools::is_write_operation(&input.tool_name) {
    operation = "write";
    if tools::is_merge_operation(&input.tool_name) {
        // Writer-level baseline for merge operations
        if !repo_id.is_empty() {
            integrity = labels::writer_integrity(&repo_id, &ctx);
        }
    } else if tools::is_delete_operation(&input.tool_name) {
        // Writer-level baseline          ← same comment, same body
        if !repo_id.is_empty() {
            integrity = labels::writer_integrity(&repo_id, &ctx);
        }
    } else if tools::is_update_operation(&input.tool_name)
        || tools::is_create_operation(&input.tool_name)
    {
        // Contributor level
        if !repo_id.is_empty() {
            integrity = labels::reader_integrity(&repo_id, &ctx);
        }
    } else if !repo_id.is_empty() {   ← same body as above, different guard
        integrity = labels::reader_integrity(&repo_id, &ctx);
    }
}

Suggested Change

Merge the two writer_integrity branches and collapse the two reader_integrity branches:

Before

if tools::is_write_operation(&input.tool_name) {
    operation = "write";
    if tools::is_merge_operation(&input.tool_name) {
        // Writer-level baseline for merge operations
        if !repo_id.is_empty() {
            integrity = labels::writer_integrity(&repo_id, &ctx);
        }
    } else if tools::is_delete_operation(&input.tool_name) {
        // Writer-level baseline
        if !repo_id.is_empty() {
            integrity = labels::writer_integrity(&repo_id, &ctx);
        }
    } else if tools::is_update_operation(&input.tool_name)
        || tools::is_create_operation(&input.tool_name)
    {
        // Contributor level
        if !repo_id.is_empty() {
            integrity = labels::reader_integrity(&repo_id, &ctx);
        }
    } else if !repo_id.is_empty() {
        integrity = labels::reader_integrity(&repo_id, &ctx);
    }
}

After

if tools::is_write_operation(&input.tool_name) {
    operation = "write";
    if tools::is_merge_operation(&input.tool_name)
        || tools::is_delete_operation(&input.tool_name)
    {
        // Writer-level baseline for merge and delete operations
        if !repo_id.is_empty() {
            integrity = labels::writer_integrity(&repo_id, &ctx);
        }
    } else if !repo_id.is_empty() {
        // Contributor level for update, create, and other write operations
        integrity = labels::reader_integrity(&repo_id, &ctx);
    }
}

Why This Matters

The current structure implies that is_update_operation || is_create_operation and the catch-all else case behave differently, when they don't. The refactored version makes the two-tier policy (merge/delete → writer; everything else → reader) immediately obvious, reducing the cognitive load on reviewers and removing the risk that a future editor adds a third handler between the two identical arms without noticing they were duplicates.

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Codebase Health Summary

• Total Rust files: 9
• Total lines: 10,927
• Areas analyzed: lib.rs, tools.rs, labels/mod.rs, labels/backend.rs, labels/constants.rs, labels/helpers.rs, labels/response_items.rs, labels/response_paths.rs, labels/tool_rules.rs
• Areas with no further improvements: (none yet — first run)

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Generated by Rust Guard Improver • Run: §24183235827

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• expires on Apr 16, 2026, 9:52 AM UTC