svelte-rs — Rust implementation of the Svelte compiler (WIP)

Demo

https://mrwaip.github.io/svelte-rs-2/

Architecture overview

https://excalidraw.com/#json=tPR4IJ3ZQmfRfF0xW1fif,Qw3c1g41YuyCLz1XmRcujw

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Feature checklist

See ROADMAP.md for the full feature checklist.

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Workflow

This project uses Claude Code with a set of specialized commands and agents.

Session Start

/status — project overview: active specs, ignored tests, next ROADMAP item, known debt

Feature Porting

1. /audit <feature> — gap analysis, create a spec and tests
2. /port specs/<file>.md — implement the next slice from the spec
3. /qa — review for material quality issues
4. /sync-docs — sync ROADMAP and CODEBASE_MAP

Test Triage

1. /explain-test <name> (optional — understand what the test covers)
2. /triage-test <name> — classify the work as local-fix, slice-gap, or spec-gap
3. /qa (optional)

Diagnostic Parity

1. /add-diagnostic-test <name> — create a focused diagnostic parity case under tasks/diagnostic_tests/
2. /diagnose-diagnostics <component|case> — isolate a false positive, false negative, or span mismatch against npm svelte/compiler
3. /port specs/<file>.md — implement the owning fix after the mismatch is reduced to one durable case

Tech Debt / Refactoring

1. /improve <description> — diagnosis, fix, and tests
2. /qa

Investigation

• /diagnose <component> — run the repro through the pipeline, isolate the root cause, add focused tests, and record follow-up work in a spec or ROADMAP.md
• /audit <feature> — gap analysis vs the reference compiler
• /explain-test <name> — what the test does and why it fails
• /bench — Rust vs JS performance

Maintenance

• /sync-docs — synchronize documentation with the code
• /add-test <name> — test-first: create a test before implementation
• /add-diagnostic-test <name> — test-first: create a diagnostic parity case before implementation

Snapshot Generation

• just generate — regenerate reference snapshots for both tasks/compiler_tests/ and tasks/diagnostic_tests/

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Building the WASM package

wasm-pack build --target web ./crates/wasm_compiler -d ../../docs/compiler

Or just playground to build WASM and serve the playground locally.

Native Node.js bindings (NAPI)

A native addon for Node.js consumers lives in crates/napi_compiler and is published as svelte-rs2 from packages/.

• just npm-smoke — debug build + local link + smoke test
• just npm-build — release build + tarballs for platform packages

Quick check against reference compiler

just quick-check path/to/component.svelte — compile a single component and diff against svelte/compiler output.

Useful dev commands

• just test-compiler — run all compiler integration tests
• just test-case <name> / just test-case-verbose <name> — single test case
• just test-diagnostics / just test-diagnostic-case <name> — diagnostic parity tests
• just clippy-strict — clippy with -D warnings
• just generate — regenerate reference snapshots
• just dump-ast '<expr>' — dump OXC ESTree JSON for a JS expression