loom-dead-code-check

Dead Code Detection

Overview

Dead code — written but never called, imported, or used — is a direct signal of incomplete integration: a function nothing calls means the feature isn't wired up. In loom it serves two roles: wiring verification (catch implemented-but-unintegrated code) and code quality (cleanup). Most valuable in integration-verify stages as a final gate over all implementation stages.

⚠️ truths is GONE as a standalone field. Put dead-code checks in the first-class dead_code_check field (a goal-backward layer, run by loom check) or in acceptance (a build/lint command that exits non-zero on findings). A top-level truths: block is rejected as an unknown field.

If dead code survives implementation it usually means: feature not wired (command unregistered, route unmounted), test code never run, refactor leftovers, or an incomplete implementation.

The dead_code_check field (preferred, first-class)

dead_code_check is a goal-backward check evaluated by loom check <stage-id>. Schema:

dead_code_check:
  command: "cargo build --message-format=short 2>&1"
  fail_patterns: ["warning: unused", "is never read", "never constructed"]
  ignore_patterns: ["generated.rs", "#[allow(dead_code)]"]

Exactly how loom evaluates it (verify/goal_backward/dead_code.rs):

1. Runs command in working_dir, 120 s timeout, capturing stdout and stderr.
2. Scans the combined output line by line.
3. A line is a violation if it contains any fail_pattern (plain substring, not regex) AND contains no ignore_pattern.
4. Each violating line becomes one gap.

⚠ The command's exit code is ignored — only output text matters. So cargo build (exit 0 with warnings) works fine; you do NOT need -D warnings. This is the key difference from an acceptance command, which passes/fails on exit code.

⚠ ignore_patterns match the whole output line, so you can suppress by symbol name, file path, or an #[allow(...)] echo — whatever appears on the tool's line. Substring, so old_helper also ignores old_helper_2.