Use just .cjs for CommonJS bundles, rather than .cjs.js.

config/helpers.ts

@@ -23,6 +23,7 @@ export function eachFile(dir: string, callback: (
 
         // Avoid re-transforming CommonJS bundle files.
         if (relPath.endsWith(".cjs.js")) return;
+        if (relPath.endsWith(".cjs")) return;
 
         // Avoid re-transforming CommonJS bundle files.
         if (relPath.endsWith(".min.js")) return;

config/prepareDist.js

@@ -70,7 +70,7 @@ entryPoints.forEach(function buildPackageJson({
     JSON.stringify({
       name: path.posix.join('@apollo', 'client', ...dirs),
       type: "module",
-      main: `${bundleName}.cjs.js`,
+      main: `${bundleName}.cjs`,
       module: 'index.js',
       types: 'index.d.ts',
       sideEffects,

config/rollup.config.js

@@ -91,7 +91,7 @@ function prepareBundle({
       return isExternal(id, parentId, true);
     },
     output: {
-      file: `${dir}/${bundleName}.cjs.js`,
+      file: `${dir}/${bundleName}.cjs`,
       format: 'cjs',
       sourcemap: true,
       exports: 'named',
@@ -109,10 +109,10 @@ export default [
   // Convert the ESM entry point to a single CJS bundle.
   prepareCJS(
     './dist/core/index.js',
-    './dist/apollo-client.cjs.js',
+    './dist/apollo-client.cjs',
   ),
   // Minify that single CJS bundle.
   prepareCJSMinified(
-    './dist/apollo-client.cjs.js',
+    './dist/apollo-client.cjs',
   ),
 ];

config/version.js

@@ -31,7 +31,7 @@ switch (process.argv[2]) {
     const {
       ApolloClient,
       InMemoryCache,
-    } = require(path.join(distRoot, "core", "core.cjs.js"));
+    } = require(path.join(distRoot, "core", "core.cjs"));
 
     // Though this may seem like overkill, verifying that ApolloClient is
     // constructible in Node.js is actually pretty useful, too!
@@ -43,15 +43,15 @@ switch (process.argv[2]) {
     // the client might have acquired during its construction.
     client.stop();
 
-    // The CommonJS dist/core/core.cjs.js file is generated from ESM modules
-    // generated by tsc, including dist/version.js, so verifying core.cjs.js
-    // exports an ApolloClient class that defines client.version also serves
-    // to verify that dist/version.js must have been correctly updated,
-    // which is convenient because dist/version.js uses ECMAScript module
-    // syntax, and is thus not importable in all versions of Node.js.
+    // The CommonJS dist/core/core.cjs file is generated from ESM modules
+    // generated by tsc, including dist/version.js, so verifying core.cjs
+    // exports an ApolloClient class that defines client.version also serves to
+    // verify that dist/version.js must have been correctly updated, which is
+    // convenient because dist/version.js uses ECMAScript module syntax, and is
+    // thus not importable in all versions of Node.js.
     assert.strictEqual(
       client.version, version,
-      "Failed to update dist/version.js and dist/core/core.cjs.js",
+      "Failed to update dist/version.js and dist/core/core.cjs",
     );
 
     break;