remove esm and use cjs output from plugins

packages/cli/package.json

@@ -61,7 +61,7 @@
     "inquirer": "^7.0.4",
     "ora": "^4.0.3",
     "react-dev-utils": "^10.2.0",
-    "react-scripts": "^3.4.0",
+    "react-scripts": "^3.4.1",
     "recursive-readdir": "^2.2.2",
     "replace-in-file": "^5.0.2",
     "rollup": "^2.1.0",

packages/cli/src/commands/plugin/build.ts

@@ -18,15 +18,13 @@ const rollup = require('rollup'); // "import" is not working for some reason...
 import rollupConfig from './rollup.config';
 
 export default async () => {
-  for (const config of rollupConfig) {
-    const inputOptions = {
-      input: config.input,
-      plugins: config.plugins,
-    };
-    const outputOptions = config.output;
+  const inputOptions = {
+    input: rollupConfig.input,
+    plugins: rollupConfig.plugins,
+  };
+  const outputOptions = rollupConfig.output;
 
-    const bundle = await rollup.rollup(inputOptions);
-    await bundle.generate(outputOptions);
-    await bundle.write(outputOptions);
-  }
+  const bundle = await rollup.rollup(inputOptions);
+  await bundle.generate(outputOptions);
+  await bundle.write(outputOptions);
 };

packages/cli/src/commands/plugin/rollup.config.ts

@@ -21,34 +21,21 @@ import resolve from '@rollup/plugin-node-resolve';
 import postcss from 'rollup-plugin-postcss';
 import image from 'rollup-plugin-image-files';
 
-const plugins = [
-  peerDepsExternal(),
-  resolve(),
-  commonjs({
-    include: ['node_modules/**', '../../node_modules/**'],
-    exclude: ['**/*.stories.js'],
-  }),
-  postcss(),
-  image(),
-  typescript(),
-];
-
-export default [
-  {
-    input: 'src/index.ts',
-    output: {
-      file: 'build/index.esm.js',
-      format: 'esm',
-      sourcemap: true,
-    },
-    plugins,
+export default {
+  input: 'src/index.ts',
+  output: {
+    file: 'build/index.cjs.js',
+    format: 'cjs',
   },
-  {
-    input: 'src/index.ts',
-    output: {
-      file: 'build/index.cjs.js',
-      format: 'cjs',
-    },
-    plugins,
-  },
-];
+  plugins: [
+    peerDepsExternal(),
+    resolve(),
+    commonjs({
+      include: ['node_modules/**', '../../node_modules/**'],
+      exclude: ['**/*.stories.js'],
+    }),
+    postcss(),
+    image(),
+    typescript(),
+  ],
+};

packages/cli/templates/default-plugin/package.json.hbs

@@ -1,7 +1,7 @@
 {
   "name": "@backstage/plugin-{{id}}",
   "version": "{{version}}",
-  "main": "build/index.esm.js",
+  "main": "build/index.cjs.js",
   "types": "build/index.d.ts",
   "license": "Apache-2.0",
   "private": true,