[brenelz]

A browser playground for learning what ReactiveScript compiles to: type .rx on the left, and the right side shows the same program written with Solid 2.0's own primitives (createSignal, createMemo, createOptimistic, createProjection, action, <Errored>, <Loading>), with the checker's diagnostics underneath. Work in progress; it is not deployed.

Compiler change

The language server's WebAssembly build (src/wasm.rs) already answers analyze and prelude over a host rx_read, so it can run from memory in a browser. It could not compile, because app::app reads the program from disk. Two small changes make it possible:

• app::app_with takes a reader in place of the disk; app::app (the Node-API build and rxc app) calls it with read_disk and behaves as before.
• serve.rs answers an app request ({entry, overlays, target, moduleName, spa, jsx}) through it. With jsx: true, each module also carries the JSX handed to Solid's compiler, printed by the new emit::view_jsx over oxc_codegen (already in the lockfile through solidjs-compiler, now a direct dependency).
• analyze takes project: false to return diagnostics without building the TSX projection, which the playground does not show. Leaving it out keeps the language server's behaviour.

The playground also turned up a parser bug that the language server shares: the recovering parse read a missing statement as an empty one without advancing, so parse_block spun on an unclosed { at the end of input. A half-typed handler such as onClick={() => { c made analyze take 8 to 27 seconds. parse_block now stops when a pass reads nothing, and the missing } is an ordinary parse error.

The napi wasm32-wasi browser build was the other candidate, but its WASI has no filesystem, so app(entry) cannot read sources there.

Playground (site/playground/)

A Vite + Solid rc.21 app. Each keystroke runs analyze (with project: false) for diagnostics and app with jsx: true for the program, under 1 ms per keystroke once the compiler is warm. The page renders before rxc.wasm arrives; the wasm is built with symbols stripped (4.8 MB), compiled while it streams, and retried if the download is cut off. The JSX is formatted with Prettier, then src/solidify.ts writes each __rt helper that is a Solid primitive underneath (spec/11 CP-4b, @reactivescript/runtime) as that primitive and strips the mangled names (v$id, w$id become id, setId). This view is a reading aid, not the code that runs. Explain notes name the .rx form behind each line. The program is kept in the URL hash.

site/.assetsignore leaves playground/ out of the static site upload, so deploying reactivescript.dev is unchanged. public/rxc.wasm is built by pnpm wasm and not checked in.

Verification

• cargo check --manifest-path compiler/Cargo.toml --all-targets
• cargo test --release --manifest-path compiler/Cargo.toml, including the new an_unclosed_block_at_the_end_of_input_stops.
• Every prefix and every one-character deletion of the six examples, replayed through analyze and app: the slowest step takes 14 ms.
• In site/playground: pnpm wasm, npx tsc -p ., pnpm build, and pnpm test with pnpm dev running: 11 Playwright checks covering the featured await lowering, Explain notes, stores, a rest prop as omit, keyed and draft projections, live updates, WRITE_TO_NON_SOURCE with its rule and guide link, every example, the URL hash, a two-module program, and no page errors.
• One round of self-review and a Codex review; the findings were fixed (operator precedence in the == rewrite, renames inside string literals, store reads scoped to their declaring block, two-module formatting, the URL after adding a file, and others).

Open

• Hosting: serving it at reactivescript.dev/playground needs a build step that has the wasm32-unknown-unknown target (the editor.yml workflow already builds it) and Vite's base: "/playground/".
• The rewrite is text-based, so unusual programs can fall back to the compiler's raw JSX, with a note saying so.
• Prop defaults stay as createMemo(() => props.x === undefined ? d : props.x) rather than merge: merge keeps an explicit undefined, while 07 §5 applies defaults on undefined.

🤖 Generated with Claude Code

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/​playwright-core@​1.65.0
	npm/​vite@​8.3.8
	npm/​highlight.js@​11.12.0
	npm/​prettier@​3.10.1
	npm/​@​solidjs/​vite-plugin@​3.0.0-next.57

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