pyreon

Context & Provider Mistakes

Generated from .agents/rules/anti-patterns.md (the same source as MCP get_anti_patterns). Each entry is a real mistake + its fix; where a detector code is listed, the linter / pyreon doctor / MCP validate catches it automatically.

A component reading context bare while sibling hooks use a fallback

Route every consumer of a context+singleton pair through one resolver.

  • @pyreon/router hooks and RouterLinkImpl resolve through getActiveRouter() (context, then the active router). A bare useContext read made <RouterLink> render a #/path href and swallow clicks after setActiveRouter(router) with no provider.

  • A component that cannot resolve its dependency degrades to native behaviour (plain href, unintercepted click, dev warning). Guard-bails run before preventDefault().

  • Test: packages/core/router/src/tests/link-dx.test.ts.

Destructuring context values

const { mode } = useContext(ctx) fires provider getters once. Keep the object and read ctx.mode inside reactive scopes.

Static provide for dynamic values

provide(ctx, "dark") is static. Provide an object with getters or an accessor: provide(ModeCtx, () => modeSignal()).

signal(newValue) to write

signal(5) reads and ignores the argument. Use signal.set(5) or signal.update(n => n + 1). Dev mode warns; the detector flags X(value) where X is a signal(...)/computed(...) const.

Detected by: signal-write-as-call — surfaced by @pyreon/lint / pyreon doctor / MCP validate.

onClick={undefined}

A nullish handler is legal and ignored (applyEventProp in runtime-dom/src/props.ts returns early for non-functions and warns only for wrong types).

  • onClick={cond ? handler : undefined} is the intended pattern.

  • The risk is a silent dead control when a handler you expected is undefined. The detector flags only the literal onClick={undefined} (omit the attribute instead).

Detected by: on-click-undefined — surfaced by @pyreon/lint / pyreon doctor / MCP validate.

Pyreon-flavored helper components in compat-mode apps without nativeCompat()

The *-compat JSX runtimes wrap user components in wrapCompatComponent, so a helper using provide() / onMount() / onUnmount() / effect() at body scope runs outside Pyreon's setup frame and breaks on re-render.

  • Call nativeCompat(MyHelper) from @pyreon/core (core/src/compat-marker.ts) so compat runtimes route it through h(). Framework components (RouterView, PyreonUI, FormProvider, …) are already marked.

  • Unit tests cannot see this (a single synchronous mount keeps context); the cpa-app-compat e2e suites (e2e/cpa-app-*-compat.spec.ts) catch it.

Context & Provider Mistakes