feat(build): Add ability to combine package-specific rollup config with standard options (#5144)

Currently, the functions which we use to generate rollup configs accept a small handful of pre-defined options for customizing the output. For greater flexibility, this adds the option of passing arbitrary rollup options, which will get merged into what is currently being generated.

Author: lobsterkatie

packages/nextjs/rollup.npm.config.js

@@ -7,6 +7,6 @@ export default makeNPMConfigVariants(
     entrypoints: ['src/index.server.ts', 'src/index.client.ts', 'src/utils/instrumentServer.ts'],
     // prevent this nextjs code from ending up in our built package (this doesn't happen automatially because the name
     // doesn't match an SDK dependency)
-    externals: ['next/router'],
+    packageSpecificConfig: { external: ['next/router'] },
   }),
 );

rollup/bundleHelpers.js

@@ -21,7 +21,7 @@ import {
 import { mergePlugins } from './utils';
 
 export function makeBaseBundleConfig(options) {
-  const { bundleType, entrypoints, jsVersion, licenseTitle, outputFileBase } = options;
+  const { bundleType, entrypoints, jsVersion, licenseTitle, outputFileBase, packageSpecificConfig } = options;
 
   const nodeResolvePlugin = makeNodeResolvePlugin();
   const sucrasePlugin = makeSucrasePlugin();
@@ -113,7 +113,7 @@ export function makeBaseBundleConfig(options) {
     node: nodeBundleConfig,
   };
 
-  return deepMerge(sharedBundleConfig, bundleTypeConfigMap[bundleType], {
+  return deepMerge.all([sharedBundleConfig, bundleTypeConfigMap[bundleType], packageSpecificConfig || {}], {
     // Plugins have to be in the correct order or everything breaks, so when merging we have to manually re-order them
     customMerge: key => (key === 'plugins' ? mergePlugins : undefined),
   });

rollup/npmHelpers.js

@@ -15,15 +15,16 @@ import {
   makeRemoveESLintCommentsPlugin,
   makeSucrasePlugin,
 } from './plugins/index.js';
+import { mergePlugins } from './utils';
 
 const packageDotJSON = require(path.resolve(process.cwd(), './package.json'));
 
 export function makeBaseNPMConfig(options = {}) {
   const {
     entrypoints = ['src/index.ts'],
     esModuleInterop = false,
-    externals: packageSpecificExternals = [],
     hasBundles = false,
+    packageSpecificConfig = {},
   } = options;
 
   const nodeResolvePlugin = makeNodeResolvePlugin();
@@ -33,7 +34,7 @@ export function makeBaseNPMConfig(options = {}) {
   const removeBlankLinesPlugin = makeRemoveBlankLinesPlugin();
   const extractPolyfillsPlugin = makeExtractPolyfillsPlugin();
 
-  return {
+  const defaultBaseConfig = {
     input: entrypoints,
 
     output: {
@@ -91,7 +92,6 @@ export function makeBaseNPMConfig(options = {}) {
       ...Object.keys(packageDotJSON.dependencies || {}),
       ...Object.keys(packageDotJSON.devDependencies || {}),
       ...Object.keys(packageDotJSON.peerDependencies || {}),
-      ...packageSpecificExternals,
     ],
 
     // TODO `'smallest'` will get rid of `isDebugBuild()` by evaluating it and inlining the result and then treeshaking
@@ -100,6 +100,11 @@ export function makeBaseNPMConfig(options = {}) {
     // treeshake: 'smallest',
     treeshake: false,
   };
+
+  return deepMerge(defaultBaseConfig, packageSpecificConfig, {
+    // Plugins have to be in the correct order or everything breaks, so when merging we have to manually re-order them
+    customMerge: key => (key === 'plugins' ? mergePlugins : undefined),
+  });
 }
 
 export function makeNPMConfigVariants(baseConfig) {