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Turbopack server HMR: inline source maps for evaled modules #90561

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Turbopack server HMR: inline source maps for evaled modules #90561

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22 changes: 20 additions & 2 deletions turbopack/crates/turbopack-ecmascript-runtime/js/src/nodejs/dev/hmr-client.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,25 @@ type NodeJsHmrPayload = {
instruction: EcmascriptMergedUpdate
}

/**
* Appends the module code with //# sourceURL and //# sourceMappingURL so
* that Node.js can resolve stack frames from `eval`ed server HMR modules back to
* their original source files. Mirrors the browser's _eval in dev-backend-dom.ts.
*/
function maybeInlineSourcemaps(entry: EcmascriptModuleEntry): string {
const [chunkPath, moduleId] = entry.url.split('?', 2)
const absolutePath = path.resolve(RUNTIME_ROOT, chunkPath)
const fileHref = url.pathToFileURL(absolutePath).href
const sourceURL = moduleId ? `${fileHref}?${moduleId}` : fileHref
let code = entry.code + '\n\n//# sourceURL=' + sourceURL
if (entry.map) {
code +=
'\n//# sourceMappingURL=data:application/json;charset=utf-8;base64,' +
Buffer.from(entry.map).toString('base64')
Comment on lines +26 to +30
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@lukesandberg lukesandberg Feb 26, 2026

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do we have to inline it? can we use a file reference here? sourceMappingUrl=file://...

this will slow down eval times (and hmr times) since our sourcemaps can contain source content already

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@lukesandberg lukesandberg Feb 26, 2026

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oic, entry.map is just the literal contents...

this thread implies you can just append the contents directly: https://issues.chromium.org/issues/41177554

but this is fine

}
return code
}

let serverHmrUpdateHandler: ((msg: NodeJsHmrPayload) => void) | null = null

function initializeServerHmr(
Expand Down Expand Up @@ -75,10 +94,9 @@ function handleNodejsUpdate(
try {
const { entries = {}, chunks = {} } = instruction

// Node.js eval function (no source maps)
const evalModuleEntry = (entry: EcmascriptModuleEntry) => {
// eslint-disable-next-line no-eval
return (0, eval)(entry.code)
return (0, eval)(maybeInlineSourcemaps(entry))
}

const { added, modified } = computeChangedModules(
Expand Down
20 changes: 17 additions & 3 deletions turbopack/crates/turbopack-tests/tests/snapshot/debug-ids/node/output/[turbopack]_runtime.js
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4 changes: 2 additions & 2 deletions ...ck/crates/turbopack-tests/tests/snapshot/debug-ids/node/output/[turbopack]_runtime.js.map
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