fix(optimizer): workaround firefox's false warning for no sources source map (#18665)

Co-authored-by: Bjorn Lu <[email protected]>

Author: hi-ogawa

packages/vite/src/node/optimizer/index.ts

@@ -673,6 +673,25 @@ export function runOptimizeDeps(
                 browserHash: metadata.browserHash,
               })
             }
+          } else {
+            // workaround Firefox warning by removing blank source map reference
+            // https://github.com/evanw/esbuild/issues/3945
+            const output = meta.outputs[o]
+            // filter by exact bytes of an empty source map
+            if (output.bytes === 93) {
+              const jsMapPath = path.resolve(o)
+              const jsPath = jsMapPath.slice(0, -4)
+              if (fs.existsSync(jsPath) && fs.existsSync(jsMapPath)) {
+                const map = JSON.parse(fs.readFileSync(jsMapPath, 'utf-8'))
+                if (map.sources.length === 0) {
+                  const js = fs.readFileSync(jsPath, 'utf-8')
+                  fs.writeFileSync(
+                    jsPath,
+                    js.slice(0, js.lastIndexOf('//# sourceMappingURL=')),
+                  )
+                }
+              }
+            }
           }
         }
 

playground/optimize-deps/dep-source-map-no-sources/all.js

@@ -0,0 +1,2 @@
+export const all = 'all'
+export { sub } from './sub.js'

playground/optimize-deps/dep-source-map-no-sources/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "@vitejs/test-dep-source-map-no-sources",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "exports": {
+    "./*": "./*"
+  }
+}

playground/optimize-deps/dep-source-map-no-sources/sub.js

@@ -0,0 +1 @@
+export const sub = 'sub'

playground/optimize-deps/index.html

@@ -299,3 +299,9 @@ <h2>Pre-bundle transitive dependency 'some-package.pdf'</h2>
   text('.dep-with-asset-ext-prebundled', isPreBundled)
   text('.dep-with-asset-ext-no-dual-package', original === reexport)
 </script>
+
+<script type="module">
+  // manually check Firefox doesn't show warning in devtool debugger
+  import * as sub from '@vitejs/test-dep-source-map-no-sources/sub.js'
+  import * as all from '@vitejs/test-dep-source-map-no-sources/all.js'
+</script>

playground/optimize-deps/package.json

@@ -29,6 +29,7 @@
     "@vitejs/test-dep-optimize-exports-with-root-glob": "file:./dep-optimize-exports-with-root-glob",
     "@vitejs/test-dep-optimize-with-glob": "file:./dep-optimize-with-glob",
     "@vitejs/test-dep-relative-to-main": "file:./dep-relative-to-main",
+    "@vitejs/test-dep-source-map-no-sources": "file:./dep-source-map-no-sources",
     "@vitejs/test-dep-with-asset-ext1.pdf": "file:./dep-with-asset-ext/dep1",
     "@vitejs/test-dep-with-asset-ext2.pdf": "file:./dep-with-asset-ext/dep2",
     "@vitejs/test-dep-with-builtin-module-cjs": "file:./dep-with-builtin-module-cjs",