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gateway-dialyzer

Run dialyzer over the Yuzu Erlang gateway. Sources the Erlang toolchain and runs rebar3 dialyzer. Use after any .erl change in gateway/ — CLAUDE.md mandates dialyzer be clean before commit because compilation success does not imply type correctness.

DevNullLtd/Yuzu

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SKILL.md3.9 KB

SKILL.md（原文）

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gateway-dialyzer

Runbook for static type analysis on the Yuzu Erlang gateway. Mandatory after every .erl change per CLAUDE.md.

Command

From the repo root:

source scripts/ensure-erlang.sh >/dev/null && \
  command -v erl >/dev/null || { echo "Erlang missing"; exit 1; }
cd gateway && rebar3 dialyzer

First run on a fresh checkout builds the PLT (persistent lookup table) for the full OTP + dependency closure — this takes 2-5 minutes. Subsequent runs are incremental and complete in 10-30 seconds. The PLT lives under _build/default/rebar3_<otp>_plt; if it gets corrupted, delete it and rerun.

Why this is mandatory

rebar.config uses warnings_as_errors for compile, so compile warnings block the build. But dialyzer warnings are separate — the compiler silently accepts:

-spec contract violations (function called with an arg that the spec rejects)
Unreachable patterns in case clauses
Dead code from structurally impossible states
Missing dependencies (functions called from modules not listed in applications)
Opaque type leaks

Dialyzer catches all of these. Skipping dialyzer is how the gateway acquires silent type bugs that only surface weeks later.

Interpreting output

No output after "Analyzing N files ..." — clean, no findings. Exit code 0.
Unknown functions: / Unknown types: — a transitive dep is missing from the applications list in yuzu_gw.app.src. Rule: if you call a function from a transitive dependency, add its owning app to applications. ctx is the canonical example — a transitive dep of grpcbox that we also call directly (ctx:background/0), so it must be listed explicitly or dialyzer can't find it in the PLT.
The call ... will never return since it differs in arguments from the success typing — the call arguments contradict the callee's -spec. Fix the caller, not the spec (unless the spec is wrong).
The variable _ can never match since previous clauses completely covered the type — dead code from a structurally impossible state. Delete the catchall. The circuit breaker's on_success/on_failure functions are the canonical example: only closed and half_open are reachable because check_circuit/1 rejects open before the RPC runs, so a _ -> ... catchall is unreachable.
Plugin gpb does not export init/1 — benign warning from rebar3 itself, not dialyzer. gpb is used via grpc config, not as a rebar3 plugin. Ignore.

Known pitfalls

Symptom	Root cause	Fix
Dialyzer can't find a function you can clearly see in a dep's source	Dep is transitive, not in `applications`	Add the app to `yuzu_gw.app.src` `applications` list
Warnings about a fallback clause you added "just in case"	The -spec declares it unreachable	Delete the clause; respect the spec
PLT-related errors after an OTP upgrade	Stale PLT from prior OTP version	`rm -rf gateway/_build/default/rebar3_*_plt` and rerun
Warnings you don't understand after adding a new dep	New dep's types weren't added to the PLT	`rebar3 dialyzer --update-plt` (automatic on next run anyway)

Workflow discipline

Per CLAUDE.md, the required sequence after any gateway .erl edit is:

rebar3 compile — catches syntax + explicit compile warnings
gateway-eunit skill — catches runtime behavior regressions
gateway-dialyzer (this skill) — catches type violations and dead code
Commit only if all three are clean

If dialyzer reports a warning you believe is wrong, do not suppress it — investigate. Every dialyzer warning that was "known and benign" has, at some point, turned out to be a real bug.

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adversarial-review

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Run an adversarial two-phase code review of a change with TWO independent reviewers — Claude and Codex — who review alone, then cross-examine each other's findings, then Claude synthesizes a single weighted verdict. Use when the user says "/adversarial-review", "adversarial review", "review this with Codex", "get Codex to review", "two-reviewer review", "cross-examine this PR", or wants a second independent model to grade a change before merge.

日本語の概要は準備中です。原文の説明を表示しています。