test_runner: simplify mock.module normalization

- Unify internal export representation into a single `moduleExports`
  object, removing the split into `defaultExport`, `hasDefaultExport`,
  and `namedExports`.
- DRY up `emitLegacyMockOptionWarning` with a lookup map instead of a
  switch statement with separate flag variables.
- Use `ObjectDefineProperty` for `defaultExport` option to be
  consistent with descriptor copying in `namedExports`.

Author: Han5991

lib/internal/test_runner/mock/loader.js

@@ -113,10 +113,10 @@ function defaultExportSource(useESM, hasDefaultExport) {
   if (!hasDefaultExport) {
     return '';
   } else if (useESM) {
-    return 'export default $__exports.defaultExport;';
+    return 'export default $__exports.moduleExports.default;';
   }
 
-  return 'module.exports = $__exports.defaultExport;';
+  return 'module.exports = $__exports.moduleExports.default;';
 }
 
 function namedExportsSource(useESM, exportNames) {
@@ -134,9 +134,9 @@ if (module.exports === null || typeof module.exports !== 'object') {
     const name = exportNames[i];
 
     if (useESM) {
-      source += `export let ${name} = $__exports.namedExports[${JSONStringify(name)}];\n`;
+      source += `export let ${name} = $__exports.moduleExports[${JSONStringify(name)}];\n`;
     } else {
-      source += `module.exports[${JSONStringify(name)}] = $__exports.namedExports[${JSONStringify(name)}];\n`;
+      source += `module.exports[${JSONStringify(name)}] = $__exports.moduleExports[${JSONStringify(name)}];\n`;
     }
   }
 

lib/internal/test_runner/mock/mock.js

@@ -1,5 +1,6 @@
 'use strict';
 const {
+  ArrayPrototypeFilter,
   ArrayPrototypePush,
   ArrayPrototypeSlice,
   Error,
@@ -61,8 +62,12 @@ const kSupportedFormats = [
   'module',
 ];
 let sharedModuleState;
-let warnedLegacyDefaultExport;
-let warnedLegacyNamedExports;
+const warnedLegacyOptions = { __proto__: null };
+const kLegacyOptionReplacements = {
+  __proto__: null,
+  defaultExport: 'options.exports.default',
+  namedExports: 'options.exports',
+};
 const {
   hooks: mockHooks,
   mocks,
@@ -187,20 +192,16 @@ class MockModuleContext {
     baseURL,
     cache,
     caller,
-    defaultExport,
     format,
     fullPath,
-    hasDefaultExport,
-    namedExports,
+    moduleExports,
     sharedState,
     specifier,
   }) {
     const config = {
       __proto__: null,
       cache,
-      defaultExport,
-      hasDefaultExport,
-      namedExports,
+      moduleExports,
       caller,
     };
 
@@ -232,8 +233,8 @@ class MockModuleContext {
         __proto__: null,
         url: baseURL,
         cache,
-        exportNames: ObjectKeys(namedExports),
-        hasDefaultExport,
+        exportNames: ArrayPrototypeFilter(ObjectKeys(moduleExports), (k) => k !== 'default'),
+        hasDefaultExport: 'default' in moduleExports,
         format,
         localVersion,
         active: true,
@@ -243,8 +244,7 @@ class MockModuleContext {
     delete Module._cache[fullPath];
     sharedState.mockExports.set(baseURL, {
       __proto__: null,
-      defaultExport,
-      namedExports,
+      moduleExports,
     });
   }
 
@@ -630,9 +630,7 @@ class MockTracker {
 
     const {
       cache,
-      defaultExport,
-      hasDefaultExport,
-      namedExports,
+      moduleExports,
     } = normalizeModuleMockOptions(options);
 
     const sharedState = setupSharedModuleState();
@@ -672,11 +670,9 @@ class MockTracker {
       baseURL: baseURL.href,
       cache,
       caller,
-      defaultExport,
       format,
       fullPath,
-      hasDefaultExport,
-      namedExports,
+      moduleExports,
       sharedState,
       specifier: mockSpecifier,
     });
@@ -819,9 +815,7 @@ function normalizeModuleMockOptions(options) {
   const { cache = false } = options;
   validateBoolean(cache, 'options.cache');
 
-  const moduleExports = {
-    __proto__: null,
-  };
+  const moduleExports = { __proto__: null };
 
   if ('exports' in options) {
     validateObject(options.exports, 'options.exports');
@@ -836,57 +830,27 @@ function normalizeModuleMockOptions(options) {
 
   if ('defaultExport' in options) {
     emitLegacyMockOptionWarning('defaultExport');
-    moduleExports.default = options.defaultExport;
-  }
-
-  const namedExports = { __proto__: null };
-  const exportNames = ObjectKeys(moduleExports);
-
-  for (let i = 0; i < exportNames.length; ++i) {
-    const name = exportNames[i];
-
-    if (name === 'default') {
-      continue;
-    }
-
-    const descriptor = ObjectGetOwnPropertyDescriptor(moduleExports, name);
-    ObjectDefineProperty(namedExports, name, descriptor);
+    ObjectDefineProperty(moduleExports, 'default', {
+      __proto__: null,
+      ...ObjectGetOwnPropertyDescriptor(options, 'defaultExport'),
+    });
   }
 
   return {
     __proto__: null,
     cache,
-    defaultExport: moduleExports.default,
-    hasDefaultExport: 'default' in moduleExports,
-    namedExports,
+    moduleExports,
   };
 }
 
 function emitLegacyMockOptionWarning(option) {
-  switch (option) {
-    case 'defaultExport':
-      if (warnedLegacyDefaultExport === true) {
-        return;
-      }
-      warnedLegacyDefaultExport = true;
-      process.emitWarning(
-        'mock.module(): options.defaultExport is deprecated. ' +
-        'Use options.exports.default instead.',
-        'DeprecationWarning',
-      );
-      break;
-    case 'namedExports':
-      if (warnedLegacyNamedExports === true) {
-        return;
-      }
-      warnedLegacyNamedExports = true;
-      process.emitWarning(
-        'mock.module(): options.namedExports is deprecated. ' +
-        'Use options.exports instead.',
-        'DeprecationWarning',
-      );
-      break;
-  }
+  if (warnedLegacyOptions[option]) return;
+  warnedLegacyOptions[option] = true;
+  process.emitWarning(
+    `mock.module(): options.${option} is deprecated. ` +
+    `Use ${kLegacyOptionReplacements[option]} instead.`,
+    'DeprecationWarning',
+  );
 }
 
 function copyOwnProperties(from, to) {
@@ -938,9 +902,7 @@ function cjsMockModuleLoad(request, parent, isMain) {
   const {
     cache,
     caller,
-    defaultExport,
-    hasDefaultExport,
-    namedExports,
+    moduleExports,
   } = config;
 
   if (cache && Module._cache[resolved]) {
@@ -949,9 +911,10 @@ function cjsMockModuleLoad(request, parent, isMain) {
     return Module._cache[resolved].exports;
   }
 
+  const hasDefaultExport = 'default' in moduleExports;
   // eslint-disable-next-line node-core/set-proto-to-null-in-object
-  const modExports = hasDefaultExport ? defaultExport : {};
-  const exportNames = ObjectKeys(namedExports);
+  const modExports = hasDefaultExport ? moduleExports.default : {};
+  const exportNames = ArrayPrototypeFilter(ObjectKeys(moduleExports), (k) => k !== 'default');
 
   if ((typeof modExports !== 'object' || modExports === null) &&
       exportNames.length > 0) {
@@ -961,7 +924,7 @@ function cjsMockModuleLoad(request, parent, isMain) {
 
   for (let i = 0; i < exportNames.length; ++i) {
     const name = exportNames[i];
-    const descriptor = ObjectGetOwnPropertyDescriptor(namedExports, name);
+    const descriptor = ObjectGetOwnPropertyDescriptor(moduleExports, name);
     ObjectDefineProperty(modExports, name, descriptor);
   }