feat(commonjs): Expose cjs detection and support offline caching

packages/commonjs/README.md

@@ -311,6 +311,26 @@ ES modules are _always_ parsed in strict mode. That means that certain non-stric
 
 Luckily, there is absolutely no good reason _not_ to use strict mode for everything — so the solution to this problem is to lobby the authors of those modules to update them.
 
+## Inter-plugin-communication
+
+This plugin exposes the result of its CommonJS file type detection for other plugins to use. You can access it via `this.getModuleInfo` or the `moduleParsed` hook:
+
+```js
+function cjsDetectionPlugin() {
+  return {
+    name: 'cjs-detection',
+    moduleParsed({
+      id,
+      meta: {
+        commonjs: { isCommonJS },
+      },
+    }) {
+      console.log(`File ${id} is CommonJS: ${isCommonJS}`);
+    },
+  };
+}
+```
+
 ## Meta
 
 [CONTRIBUTING](/.github/CONTRIBUTING.md)

packages/commonjs/package.json

@@ -47,7 +47,7 @@
     "require"
   ],
   "peerDependencies": {
-    "rollup": "^2.22.0"
+    "rollup": "^2.30.0"
   },
   "dependencies": {
     "@rollup/pluginutils": "^3.1.0",
@@ -63,7 +63,7 @@
     "@rollup/plugin-node-resolve": "^8.4.0",
     "locate-character": "^2.0.5",
     "require-relative": "^0.8.7",
-    "rollup": "^2.23.0",
+    "rollup": "^2.30.0",
     "shx": "^0.3.2",
     "source-map": "^0.7.3",
     "source-map-support": "^0.5.19",

packages/commonjs/src/index.js

@@ -103,14 +103,13 @@ export default function commonjs(options = {}) {
       !dynamicRequireModuleSet.has(normalizePathSlashes(id)) &&
       (!hasCjsKeywords(code, ignoreGlobal) || (isEsModule && !options.transformMixedEsModules))
     ) {
-      setIsCjsPromise(id, false);
-      return null;
+      return { meta: { commonjs: { isCommonJS: false } } };
     }
 
     // avoid wrapping in createCommonjsModule, as this is a commonjsRegister call
     const disableWrap = isModuleRegistrationProxy(id, dynamicRequireModuleSet);
 
-    const transformed = transformCommonjs(
+    return transformCommonjs(
       this.parse,
       code,
       id,
@@ -124,9 +123,6 @@ export default function commonjs(options = {}) {
       commonDir,
       ast
     );
-
-    setIsCjsPromise(id, isEsModule ? false : Boolean(transformed));
-    return transformed;
   }
 
   return {
@@ -201,20 +197,25 @@ export default function commonjs(options = {}) {
         !id.startsWith(DYNAMIC_JSON_PREFIX) &&
         (!filter(id) || !extensions.includes(extName))
       ) {
-        setIsCjsPromise(id, null);
         return null;
       }
 
-      let transformed;
       try {
-        transformed = transformAndCheckExports.call(this, code, id);
+        return transformAndCheckExports.call(this, code, id);
       } catch (err) {
-        transformed = null;
-        setIsCjsPromise(id, false);
-        this.error(err, err.loc);
+        return this.error(err, err.loc);
       }
+    },
 
-      return transformed;
+    moduleParsed({ id, meta: { commonjs } }) {
+      if (commonjs) {
+        const isCjs = commonjs.isCommonJS;
+        if (isCjs != null) {
+          setIsCjsPromise(id, isCjs);
+          return;
+        }
+      }
+      setIsCjsPromise(id, null);
     }
   };
 }

packages/commonjs/src/is-cjs.js

@@ -1,4 +1,3 @@
-/* eslint-disable no-undefined */
 const isCjsPromises = new Map();
 
 export function getIsCjsPromise(id) {
@@ -8,7 +7,7 @@ export function getIsCjsPromise(id) {
   const promise = new Promise((resolve) => {
     isCjsPromise = {
       resolve,
-      promise: undefined
+      promise: null
     };
     isCjsPromises.set(id, isCjsPromise);
   });
@@ -22,9 +21,9 @@ export function setIsCjsPromise(id, resolution) {
   if (isCjsPromise) {
     if (isCjsPromise.resolve) {
       isCjsPromise.resolve(resolution);
-      isCjsPromise.resolve = undefined;
+      isCjsPromise.resolve = null;
     }
   } else {
-    isCjsPromises.set(id, { promise: Promise.resolve(resolution), resolve: undefined });
+    isCjsPromises.set(id, { promise: Promise.resolve(resolution), resolve: null });
   }
 }

packages/commonjs/src/transform.js

@@ -560,8 +560,7 @@ export function transformCommonjs(
     !usesCommonjsHelpers &&
     (ignoreGlobal || !uses.global)
   ) {
-    // not a CommonJS module
-    return null;
+    return { meta: { commonjs: { isCommonJS: false } } };
   }
 
   const importBlock = `${(usesCommonjsHelpers
@@ -698,5 +697,10 @@ export function transformCommonjs(
   code = magicString.toString();
   const map = sourceMap ? magicString.generateMap() : null;
 
-  return { code, map, syntheticNamedExports: isEsModule ? false : '__moduleExports' };
+  return {
+    code,
+    map,
+    syntheticNamedExports: isEsModule ? false : '__moduleExports',
+    meta: { commonjs: { isCommonJS: !isEsModule } }
+  };
 }

packages/commonjs/test/fixtures/function/expose-file-type-detection/_config.js

@@ -0,0 +1,33 @@
+const path = require('path');
+
+const ID_MAIN = path.join(__dirname, 'main.js');
+const ID_OTHER = path.join(__dirname, 'other.js');
+
+module.exports = {
+  description: 'exposes cjs file type detection to other plugins',
+  options: {
+    input: [ID_MAIN, ID_OTHER],
+    plugins: [
+      {
+        moduleParsed({
+          id,
+          meta: {
+            commonjs: { isCommonJS }
+          }
+        }) {
+          if (id === ID_MAIN) {
+            if (isCommonJS !== false) {
+              throw new Error(
+                `Main file wrongly detected: isCommonJS === ${JSON.stringify(isCommonJS)}`
+              );
+            }
+          } else if (isCommonJS !== true) {
+            throw new Error(
+              `Other file wrongly detected: isCommonJS === ${JSON.stringify(isCommonJS)}`
+            );
+          }
+        }
+      }
+    ]
+  }
+};

packages/commonjs/test/fixtures/function/expose-file-type-detection/main.js

@@ -0,0 +1,3 @@
+import foo from './other.js';
+
+t.is(foo, 'foo');

packages/commonjs/test/fixtures/function/expose-file-type-detection/other.js

@@ -0,0 +1 @@
+module.exports = 'foo';

packages/commonjs/test/fixtures/samples/caching/dep.js

@@ -0,0 +1 @@
+exports.dep = 42;

packages/commonjs/test/fixtures/samples/caching/main.js

@@ -0,0 +1,3 @@
+const dep = require('./dep');
+
+console.log(dep);

packages/commonjs/test/fixtures/samples/caching/rollupWorker.js

@@ -0,0 +1,20 @@
+const { workerData, parentPort } = require('worker_threads');
+
+const { rollup } = require('rollup');
+
+const commonjs = require('../../../../dist/index');
+const { getCodeFromBundle } = require('../../../helpers/util');
+
+generateCode(workerData);
+
+async function generateCode(cache) {
+  const code = await getCodeFromBundle(
+    await rollup({
+      input: 'fixtures/samples/caching/main.js',
+      cache,
+      plugins: [commonjs()]
+    })
+  );
+
+  parentPort.postMessage(code);
+}