fix: merge build.rolldownOptions.output.minify correctly

packages/vite/src/node/__tests__/build.spec.ts

@@ -579,6 +579,60 @@ describe('resolveBuildOutputs', () => {
       )
     })
   })
+
+  describe('output minify and comments resolution in resolveRolldownOptions', () => {
+    const buildProjectRoot = resolve(dirname, 'packages/build-project')
+
+    test('merges a partial output.minify object with the lib defaults', async () => {
+      const builder = await createBuilder({
+        root: buildProjectRoot,
+        logLevel: 'silent',
+        build: {
+          minify: 'oxc',
+          lib: { ...baseLibOptions, formats: ['es'] },
+          rolldownOptions: {
+            output: {
+              minify: { mangle: { keepNames: true } },
+            },
+          },
+        },
+      })
+      const options = resolveRolldownOptions(
+        builder.environments.client,
+        new ChunkMetadataMap(),
+      )
+      const outputs = options.output!
+      const output = Array.isArray(outputs) ? outputs[0] : outputs
+      expect(output.minify).toStrictEqual({
+        compress: true,
+        mangle: { keepNames: true },
+        codegen: false,
+      })
+    })
+
+    test('keeps an explicit boolean output.minify untouched', async () => {
+      const builder = await createBuilder({
+        root: buildProjectRoot,
+        logLevel: 'silent',
+        build: {
+          minify: 'oxc',
+          lib: { ...baseLibOptions, formats: ['es'] },
+          rolldownOptions: {
+            output: {
+              minify: false,
+            },
+          },
+        },
+      })
+      const options = resolveRolldownOptions(
+        builder.environments.client,
+        new ChunkMetadataMap(),
+      )
+      const outputs = options.output!
+      const output = Array.isArray(outputs) ? outputs[0] : outputs
+      expect(output.minify).toBe(false)
+    })
+  })
 })
 
 describe('resolveLibFilename', () => {

packages/vite/src/node/build.ts

@@ -745,6 +745,20 @@ export function resolveRolldownOptions(
             findNearestPackageData(root, packageCache)?.data.type,
           )
         : 'js'
+    const resolvedMinify =
+      options.minify === 'oxc'
+        ? libOptions && (format === 'es' || format === 'esm')
+          ? {
+              compress: true,
+              mangle: true,
+              // Do not minify whitespace for ES lib output since that would remove
+              // pure annotations and break tree-shaking
+              codegen: false,
+            }
+          : true
+        : options.minify === false
+          ? 'dce-only'
+          : false
     return {
       dir: outDir,
       // Default format is 'es' for regular and for SSR builds
@@ -786,22 +800,15 @@ export function resolveRolldownOptions(
           (typeof input === 'string' || Object.keys(input).length === 1))
           ? false
           : undefined),
-      minify:
-        options.minify === 'oxc'
-          ? libOptions && (format === 'es' || format === 'esm')
-            ? {
-                compress: true,
-                mangle: true,
-                // Do not minify whitespace for ES lib output since that would remove
-                // pure annotations and break tree-shaking
-                codegen: false,
-              }
-            : true
-          : options.minify === false
-            ? 'dce-only'
-            : false,
       topLevelVar: true,
       ...output,
+      minify:
+        output.minify === undefined
+          ? resolvedMinify
+          : typeof output.minify === 'object' &&
+              typeof resolvedMinify === 'object'
+            ? { ...resolvedMinify, ...output.minify }
+            : output.minify,
       comments:
         typeof output.comments === 'boolean'
           ? output.comments