Custom syntax highlighting now works in Quarto Hub projects#187
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The hub-client's project-rendering path was dropping user_grammars
because RenderToHtmlRenderer constructed its own per-page
RenderContext with no API for attaching a provider. Result: any qmd
under a `_quarto.yml` ancestor rendered fenced blocks for
user-grammar languages (e.g. the highlighting/03-user-grammar-toml
fixture) unhighlighted, even though the single-file render path was
wired correctly.
Migrate `RenderContext::user_grammar_provider` and the matching
`StageContext` field from `Option<Box<dyn UserGrammarProvider>>` to
`Option<Rc<RefCell<dyn UserGrammarProvider>>>` so a single handle
can be shared across every page a renderer touches without being
consumed. Add `RenderToHtmlRenderer::with_user_grammars(...)` and
install the provider on each per-page `RenderContext`. Update the
WASM project entry point `render_project_active_page_to_response`
to wrap the incoming `JsUserGrammars` in `Rc<RefCell<_>>` and pass
it through instead of dropping it.
The pipeline-internal `.take()` becomes `.clone()` so the `Rc` is
shared with the `StageContext` rather than transferred — matters
for multi-page renders that reuse the same renderer.
Plan + investigation notes:
`claude-notes/plans/2026-05-10-thread-user-grammars-renderer.md`.
Tests: new `crates/quarto-core/tests/render_to_html_user_grammars.rs`
drives `RenderToHtmlRenderer` through the orchestrator with a stub
provider and asserts the rendered HTML carries the matching
`<span class="hl-...">` wrapper. Confirmed it fails at HEAD without
the wiring and passes after.
End-to-end harness fixes folded in (without these the
highlighting/03-user-grammar-toml.qmd e2e fixture can't actually
exercise the fix in a browser):
- smokeAllDiscovery.ts: detect binary fixture extensions (.wasm
grammars + common image/font types), read as bytes, base64-
encode, and tag `contentType: 'binary'` with a matching
mimeType so the Automerge sync client routes them as binary
documents instead of corrupting them through utf-8 decoding.
Add `contentType`/`mimeType` fields on `DiscoveredTest` and
forward them in smoke-all.spec.ts.
- previewExtraction.ts::getPreviewHtml: derive a userGrammars
context from VFS state (vfsListFiles + vfsReadFile /
vfsReadBinaryFile, with the /project/ prefix stripped to match
discoverUserGrammars's project-relative shape) so the re-render
matches what Preview.tsx → automergeSync produces in the live
iframe.
End-to-end verification (snippet from the iframe at assertion time):
<pre class="sourceCode toml" …><code><span class="hl-property">
<span class="hl-type">name</span> <span class="hl-operator">=</span>
<span class="hl-string">"example"</span></span> …
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I uncovered a failing test when running hub e2e tests on Playwright; Claude's fix sounds reasonable.
crates/quarto/tests/smoke-all/highlighting/03-user-grammar/03-user-grammar-toml.qmdSummary
_quarto/grammars/<lang>/only highlighted code blocks in single-file documents. The moment a qmd file lived under a_quarto.ymlancestor, the hub-client routed throughrenderPageInProject→render_project_active_page_to_response, which literally discarded the grammars handle (let _ = user_grammars;).user_grammarsthroughRenderToHtmlRendererto the per-pageRenderContext, soCodeHighlightStageconsults the sameJsUserGrammarshandle the single-file path was already wired for.RenderContext::user_grammar_provider(and the matchingStageContextfield) move fromOption<Box<dyn UserGrammarProvider>>toOption<Rc<RefCell<dyn UserGrammarProvider>>>so one handle can be shared across every page a renderer touches.highlighting/03-user-grammar-toml.qmdsmoke-all fixture can actually verify the fix in a browser: binary fixture loading (.wasmgrammars were being read as utf-8 and corrupted before reaching Automerge), andgetPreviewHtmlnow passes a VFS-deriveduserGrammarscontext so the re-render matches the live iframe.bd-izfv. Plan + investigation:
claude-notes/plans/2026-05-10-thread-user-grammars-renderer.md.Test plan
cargo build --workspacecargo nextest run --workspace— 8805 passedcargo nextest run -p quarto-core --test render_to_html_user_grammars— passes; confirmed failing with the wiring temporarily revertedcargo xtask verify— all 9 steps greennpx playwright test --grep "user-grammar" smoke-all.spec.ts— passes; iframe innerHTML at assertion time shows<pre class="sourceCode toml">…<span class="hl-string">"example"</span>(snippet recorded in the plan's "Phase 4 end-to-end verification artifact" section)Full
cargo xtask verify --e2ehad 6 unrelated CI-load timeout flakes — the kind documented inbc562bd4's commit message — all of which passed when re-run in isolation. The user-grammar fixture itself was the only e2e test directly relevant to this change.