docs: add Claude Code contributor skills for firmware code quality (#2212)

2026-05-30 23:30:18 +03:00
parent ebf0413fe1
commit d83605e003
7 changed files with 330 additions and 0 deletions
@@ -0,0 +1,56 @@
+---
+name: control-flow-clarity
+description: Branching and state-modeling clarity in C/C++. Use when writing or refactoring logic that branches on discrete values: if/else-if ladders, status flags, mode or state ints, or anything that should be an enum plus an exhaustive switch. Covers enum class over magic ints, exhaustive switch over nested if, early-return guard clauses, table dispatch, and when each is the right call.
+---
+
+# Control-Flow Clarity
+
+The goal: a reviewer verifies correctness by reading, not by tracing. Branching
+that mirrors the problem's shape is self-evident; branching that encodes it in
+ad-hoc ints and nesting forces the reader to reconstruct intent.
+
+## Core moves
+
+- **Model a closed set of states/modes as an `enum class`, not ints or bools.**
+  A variable kept honest by a comment ("0 = hidden, 1 = showing, 2 = confirm")
+  is a latent bug. Make it an enum and the comment becomes the type.
+- **Dispatch on an enum with an exhaustive `switch`, no `default`.** This
+  codebase relies on it: omitting `default` lets the compiler flag the
+  unhandled case when someone adds an enum value. A `default:` that swallows the
+  unknown case throws that safety away. Add `default` only when "every other
+  value does nothing" is a deliberate, documented decision.
+- **Replace nested `if/else-if` ladders that branch on one discriminant with a
+  `switch`.** If each branch only maps input to a value, prefer a lookup table
+  (`static constexpr` array) over both.
+- **Prefer early-return guard clauses over nested success bodies.** Handle the
+  error/empty/skip cases first and return; keep the main path at the left
+  margin.
+
+## When NOT to switch
+
+- Branches test unrelated conditions, not one discriminant: a guarded `if`
+  sequence is honest; a switch would be forced.
+- Two outcomes on a genuine boolean: keep the `if`.
+- The discriminant is an open or unbounded set (arbitrary ints, strings): table
+  or map, not a switch.
+
+## Enum hygiene
+
+- `enum class` by default for type safety. Plain `enum` only when values must
+  implicitly convert (e.g. a value that doubles as a UI dropdown index), and
+  then give it a trailing `_COUNT` sentinel for safe bounds/iteration, matching
+  the existing settings enums.
+- Name the discriminant after what it selects, not its storage:
+  `Orientation orientation`, not `uint8_t mode`.
+- No magic numeric codes for states. If you write a comment mapping numbers to
+  meanings, you owe an enum.
+
+## Self-review
+
+- [ ] No int/bool standing in for a closed set of modes; it is an `enum class`.
+- [ ] Enum dispatch is an exhaustive `switch` with no catch-all `default` (or
+      the `default` is a documented deliberate choice).
+- [ ] No nested if/else-if ladder on a single discriminant that should be a
+      switch or a table.
+- [ ] Error/skip cases are early-return guards; the happy path is not buried.
+- [ ] No magic numbers where a named enum or `constexpr` would state the intent.