turbopack: move CSS module composes validation from code generation to resolving - #92582
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… phase CssModuleComposesIssue was only emitted during chunk_item_content() (code generation), which meant get_compilation_issues (module graph only) could not surface these errors. Move the validation into module_references() so it runs during graph building. Add e2e test with a CSS module composing from a .txt file to verify the issue is detected. Co-Authored-By: Claude <noreply@anthropic.com>
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…::resolve_reference Instead of validating in module_references(), move the logic into the reference itself. Introduce a CssModuleComposable marker trait in compose.rs; EcmascriptCssModule implements it. resolve_reference() now validates both cases (unresolvable + non-CSS-module target) and emits CssModuleComposesIssue directly, making the issue available during module graph traversal (e.g. get_compilation_issues) without coupling the validation to the consumer (module_references or codegen). Co-Authored-By: Claude <noreply@anthropic.com>
sokra
marked this pull request as ready for review
April 10, 2026 10:47
mischnic
reviewed
Apr 10, 2026
Both types live in the same crate, so compose.rs can import EcmascriptCssModule directly. The marker trait and its impl were unnecessary indirection. Co-Authored-By: Claude <noreply@anthropic.com>
mischnic
approved these changes
Apr 10, 2026
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What?
Move the validation that can produce
CssModuleComposesIssuefrom code generation (chunk_item_content) to the reference's ownresolve_reference()method, so these errors are surfaced during resolving rather than only during bundling.Two validation checks are moved into
CssModuleComposeReference::resolve_reference():composes: ... from "...";target module can't be resolved (unresolvable reference)composes: ... from "...";target module is not a CSS module (e.g. composing from a.jsor.txtfile)The
IssueStageis updated fromCodeGentoResolveto reflect the new phase.Code generation still handles the error cases gracefully (skipping broken references with
continue) — it just no longer re-emits the issue since it is already emitted byresolve_reference().Why?
get_compilation_issues(used by the MCP server and other tooling) only builds the module graph — it does not run code generation. Previously, bothCssModuleComposesIssuevariants were only emitted duringchunk_item_content(), which meant they were invisible toget_compilation_issues. Developers using the MCPget_compilation_issuestool would not see errors from brokencomposesreferences until an actual build/bundle was triggered.Since
resolve_reference()is called as part of module graph traversal, emitting the issue there means it is captured byget_compilation_issuesalongside other resolve-phase errors.How?
turbopack-css/src/references/compose.rsCssModuleComposeReference::resolve_reference()is changed fromfntoasync fn. It callscss_resolveas before, then awaitsfirst_module()on the result and validates:CssModuleComposable→ emit "not a CSS module" issueCssModuleComposesIssueand itsIssueimpl are moved here frommodule_asset.rs, now usingResolvedVc<FileSystemPath>(fromorigin_path()) as the issue location rather than theIssueSourceof the composing file.CssModuleComposablemarker trait (#[turbo_tasks::value_trait]) is defined here.resolve_reference()uses atry_sidecastto this trait to check whether the resolved module is a valid compose target — avoiding a hard dependency onEcmascriptCssModulefrom withincompose.rs.turbopack-css/src/module_asset.rsEcmascriptCssModuleimplementsCssModuleComposable, marking it as a validcomposes:target.module_references()is reverted to its original simple form — it only collects references without any validation.Issue,IssueExt,IssueSource, etc.) are removed.Test fixtures (
test/development/mcp-server/fixtures/compilation-errors-app/app/css-composes-error/)styles.module.css— CSS module withcomposes: something from './not-a-css-module.txt'not-a-css-module.txt— a plain text file (resolves but is not a CSS module)page.tsx— page importing the broken CSS moduletest/development/mcp-server/mcp-server-get-compilation-issues.test.tsshould detect CSS module composes errorsverifies the issue is surfaced viaget_compilation_issues.