feat(cva): add boolean variant shorthand

[joe-bell]

Description

Adds a boolean variant shorthand to cva@beta (tracked in Linear as JB-251): assigning a class value directly to a variant name now declares an on/off variant.

cva({ variants: { disabled: "opacity-50" } });
// expands to
cva({ variants: { disabled: { true: "opacity-50", false: null } } });

variants: { busy: null } declares a classless boolean variant that still participates in props, compoundVariants, and getSchema.

Details:

• Any non-plain-object value (string, number, array, null) is treated as shorthand. Plain objects always stay variant maps, since a clsx class dictionary structurally overlaps one; wrap a dictionary in an array to use it as shorthand. boolean/undefined/bigint are rejected as shorthand values (bigint because clsx silently drops bigints, so it could never render).
• Shorthand is normalized once at cva() build time (with a no-allocation fast path when no shorthand is present), so the resolution loop, composition merging, component.config.variants, and getSchema all see the expanded { true, false } map. getSchema reports shorthand variants as { values: [true, false] }.
• VariantProps infers boolean for shorthand entries, and defaultVariants/compoundVariants accept booleans for them.
• Composition type fix (uncovered by hardening review, pre-existing latent bug for longhand): MergedVariants used to intersect composed components' variant maps, and TS reduces conflicting option values (null & "x", or two shorthands' differing true classes) to never, poisoning VariantProps/getSchema to string | number | symbol. It is now a right-biased fold over the composed tuple (reusing MergeVariantShapes), mirroring the runtime mergeVariants reduce order — option keys still union across components.
• Benchmark: a feature-detected Call component (boolean shorthand) scenario (same pattern as supportsComposes) keeps baseline deltas meaningful against published versions that lack the shorthand.
• Docs: new Boolean variants section, plus updates to the API reference, What's New, Composing Components, and TypeScript pages. The two examples whose disabled maps matched the shorthand expansion byte-for-byte (react-with-tailwindcss, astro-with-tailwindcss) now use it.

Three TypeScript inference traps were found and fixed along the way, recorded in AGENTS.md Learnings: the schema value conditional must be non-distributive ([T] extends [U]) or literal defaultVariants values widen; and neither the local-over-composed nor the composed-over-composed variants merge can be a plain intersection (unit-type intersection reduction collapses conflicting option maps to never).

Additional context

• Verified beyond unit tests (113 in the cva suite, 282 workspace-wide): packed-artifact consumer check per the AGENTS.md procedure (pnpm pack + tsc --strict --declaration under nodenext, including a composed-conflict component) confirms no internal types leak into emitted declarations; attw + publint build gates pass; all docs // => output comments executed against the built package; bench smoke run confirms the new scenario registers.
• Worth a reviewer's eye: the shorthand discrimination rule (plain object = variant map, everything else = shorthand) and the MergedVariants fold ordering (later composed components win per option key, matching the runtime reduce).

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Follow the Style Guide.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).

🤖 Generated with Claude Code

https://claude.ai/code/session_01VaQeVqbK9krHwPoFPjrP1M

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	cva	4d78fa2	Commit Preview URL Branch Preview URL	Jul 16 2026, 06:15 AM

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Benchmarks

Comparing this PR's local benchmark run against the latest published npm versions.

Aim for higher ops/s. Treat deltas within ±5% as noise.

class-variance-authority

Note

class-variance-authority is in maintenance mode, and its latest npm baseline predates the tsdown build migration. Treat the deltas here as indicative.

Task	This PR	0.7.1	Δ
cva (runtime) component call with defaults	606,892 ops/s ±0.28%	618,999 ops/s ±0.27%	-2.0%
cva (runtime) component call with props	97,851 ops/s ±0.29%	98,678 ops/s ±0.27%	-0.8%
cx (runtime) class join	5,815,710 ops/s ±0.31%	6,063,499 ops/s ±0.08%	-4.1%
cva (static) component definition	15,442,537 ops/s ±0.08%	13,999,413 ops/s ±0.32%	🟢 +10.3%
compose (static + runtime) define, join and call	507,856 ops/s ±0.26%	519,184 ops/s ±0.34%	-2.2%

cva

Task	This PR	1.0.0-beta.7 (beta)	Δ
cva (runtime) component call with defaults	616,274 ops/s ±0.22%	618,062 ops/s ±0.29%	-0.3%
cva (runtime) component call with props	98,131 ops/s ±0.22%	96,442 ops/s ±0.26%	+1.8%
cx (runtime) class join	5,095,701 ops/s ±0.14%	4,924,145 ops/s ±0.14%	+3.5%
cva (static) component definition	1,572,004 ops/s ±0.11%	1,889,520 ops/s ±0.32%	🔴 -16.8%
composes property (static + runtime) define, join and call	246,329 ops/s ±0.36%	251,301 ops/s ±0.22%	-2.0%

_{Commit affd871 · Node v24.18.0 · linux x64 · 2026-07-15T13:59:19.126Z}

_{These benchmarks ran in CI on this PR's code. The comment checks that the report looks valid before posting it, but it cannot guarantee the numbers are correct. If you see a large change, re-run the benchmarks locally before treating it as a real improvement or regression.}