fix(injectSourcesContent): warn once per sourcemap for missing sources

vitejs#2904

packages/vite/src/node/server/sourcemap.ts

@@ -1,29 +1,66 @@
-import { promises as fs } from 'fs'
 import path from 'path'
+import { promises as fs } from 'fs'
+import { Logger } from '../logger'
+import { createDebugger } from '../utils'
 import { ModuleGraph } from './moduleGraph'
 
+const isDebug = !!process.env.DEBUG
+const debug = createDebugger('vite:sourcemap', {
+  onlyWhenFocused: true
+})
+
+interface SourceMapLike {
+  sources: string[]
+  sourcesContent?: (string | null)[]
+  sourceRoot?: string
+}
+
 export async function injectSourcesContent(
-  map: { sources: string[]; sourcesContent?: string[]; sourceRoot?: string },
+  map: SourceMapLike,
   file: string,
+  logger: Logger,
   moduleGraph?: ModuleGraph
 ): Promise<void> {
-  const sourceRoot = await fs.realpath(
-    path.resolve(path.dirname(file), map.sourceRoot || '')
-  )
-  const needsContent = !map.sourcesContent
-  if (needsContent) {
-    map.sourcesContent = []
-  }
-  await Promise.all(
-    map.sources.filter(Boolean).map(async (sourcePath, i) => {
-      const mod = await moduleGraph?.getModuleByUrl(sourcePath)
-      sourcePath = mod?.file || path.resolve(sourceRoot, decodeURI(sourcePath))
-      if (moduleGraph) {
-        map.sources[i] = sourcePath
-      }
-      if (needsContent) {
-        map.sourcesContent![i] = await fs.readFile(sourcePath, 'utf-8')
+  let sourceRoot: string | undefined
+  try {
+    // The source root is undefined for virtual modules and permission errors.
+    sourceRoot = await fs.realpath(
+      path.resolve(path.dirname(file), map.sourceRoot || '')
+    )
+  } catch {}
+
+  const { sourcesContent } = map
+  const missingSources: string[] = []
+  map.sourcesContent = await Promise.all(
+    map.sources.map((sourcePath, i) => {
+      if (sourcePath) {
+        sourcePath = decodeURI(sourcePath)
+        const mod = await moduleGraph?.getModuleByUrl(sourcePath)
+        if (mod.file) {
+          sourcePath = mod.file
+          map.sources[i] = sourceRoot
+            ? path.relative(sourceRoot, sourcePath)
+            : sourcePath
+        } else if (sourceRoot) {
+          sourcePath = path.resolve(sourceRoot, sourcePath)
+        }
+        if (sourcesContent) {
+          return sourcesContent[i]
+        }
+        return fs.readFile(sourcePath, 'utf-8').catch(() => {
+          missingSources.push(sourcePath)
+          return null
+        })
       }
+      return null
     })
   )
+
+  // Use this command…
+  //    DEBUG="vite:sourcemap" vite build
+  // …to log the missing sources.
+  if (missingSources.length) {
+    logger.warnOnce(`Sourcemap for "${file}" points to missing source files`)
+    isDebug && debug(`Missing sources:\n  ` + missingSources.join(`\n  `))
+  }
 }

packages/vite/src/node/server/transformRequest.ts

@@ -144,7 +144,7 @@ export async function transformRequest(
   if (map && mod.file) {
     map = (typeof map === 'string' ? JSON.parse(map) : map) as SourceMap
     if (map.mappings && !map.sourcesContent) {
-      await injectSourcesContent(map, mod.file)
+      await injectSourcesContent(map, mod.file, logger)
     }
   }