feat(node-resolve): support package entry points

packages/node-resolve/README.md

@@ -34,16 +34,34 @@ export default {
   input: 'src/index.js',
   output: {
     dir: 'output',
-    format: 'cjs'
+    format: 'cjs',
   },
-  plugins: [nodeResolve()]
+  plugins: [nodeResolve()],
 };
 ```
 
 Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#command-line-reference) or the [API](https://www.rollupjs.org/guide/en/#javascript-api).
 
 ## Options
 
+### `exportConditions`
+
+Type: `Array[...String]`<br>
+Default: `[]`
+
+Additional conditions of the package.json exports field to match when resolving modules. By default, this plugin looks for the `'default', 'module', 'import']` conditions when resolving imports.
+
+When using `@rollup/plugin-commonjs` v16 or higher, this plugin will use the `['default', 'module', 'import']` conditions when resolving require statements.
+
+Setting this option will add extra conditions on top of the default conditions. See https://nodejs.org/api/packages.html#packages_conditional_exports for more information.
+
+### `browser`
+
+Type: `Boolean`<br>
+Default: `false`
+
+If `true`, instructs the plugin to use the `"browser"` property in `package.json` files to specify alternative files to load for bundling. This is useful when bundling for a browser environment. Alternatively, a value of `'browser'` can be added to the `mainFields` option. If `false`, any `"browser"` properties in package files will be ignored. This option takes precedence over `mainFields`.
+
 ### `browser`
 
 Type: `Boolean`<br>
@@ -164,9 +182,9 @@ export default {
   output: {
     file: 'bundle.js',
     format: 'iife',
-    name: 'MyModule'
+    name: 'MyModule',
   },
-  plugins: [resolve(), commonjs()]
+  plugins: [resolve(), commonjs()],
 };
 ```
 
@@ -187,6 +205,19 @@ export default ({
 })
 ```
 
+## Resolving require statements
+
+According to [NodeJS module resolution](https://nodejs.org/api/packages.html#packages_package_entry_points) `require` statements should resolve using the `require` condition in the package exports field, while es modules should use the `import` condition.
+
+The node resolve plugin uses `import` by default, you can opt into using the `require` semantics by passing an extra option to the resolve function:
+
+```js
+this.resolve(importee, importer, {
+  skipSelf: true,
+  custom: { 'node-resolve': { isRequire: true } },
+});
+```
+
 ## Meta
 
 [CONTRIBUTING](/.github/CONTRIBUTING.md)

packages/node-resolve/package.json

@@ -65,7 +65,7 @@
     "@babel/core": "^7.10.5",
     "@babel/plugin-transform-typescript": "^7.10.5",
     "@rollup/plugin-babel": "^5.1.0",
-    "@rollup/plugin-commonjs": "^14.0.0",
+    "@rollup/plugin-commonjs": "^16.0.0",
     "@rollup/plugin-json": "^4.1.0",
     "es5-ext": "^0.10.53",
     "rollup": "^2.23.0",

packages/node-resolve/src/index.js

@@ -7,13 +7,8 @@ import isModule from 'is-module';
 
 import { isDirCached, isFileCached, readCachedFile } from './cache';
 import { exists, readFile, realpath } from './fs';
-import {
-  getMainFields,
-  getPackageInfo,
-  getPackageName,
-  normalizeInput,
-  resolveImportSpecifiers
-} from './util';
+import { resolveImportSpecifiers } from './resolveImportSpecifiers';
+import { getMainFields, getPackageInfo, getPackageName, normalizeInput } from './util';
 
 const builtins = new Set(builtinList);
 const ES6_BROWSER_EMPTY = '\0node-resolve:empty.js';
@@ -29,6 +24,10 @@ const deepFreeze = (object) => {
 
   return object;
 };
+
+const baseConditions = ['default', 'module'];
+const baseConditionsEsm = [...baseConditions, 'import'];
+const baseConditionsCjs = [...baseConditions, 'require'];
 const defaults = {
   customResolveOptions: {},
   dedupe: [],
@@ -42,6 +41,8 @@ export const DEFAULTS = deepFreeze(deepMerge({}, defaults));
 export function nodeResolve(opts = {}) {
   const options = Object.assign({}, defaults, opts);
   const { customResolveOptions, extensions, jail } = options;
+  const conditionsEsm = [...baseConditionsEsm, ...(options.exportConditions || [])];
+  const conditionsCjs = [...baseConditionsCjs, ...(options.exportConditions || [])];
   const warnings = [];
   const packageInfoCache = new Map();
   const idToPackageInfo = new Map();
@@ -93,7 +94,7 @@ export function nodeResolve(opts = {}) {
       isDirCached.clear();
     },
 
-    async resolveId(importee, importer) {
+    async resolveId(importee, importer, opts) {
       if (importee === ES6_BROWSER_EMPTY) {
         return importee;
       }
@@ -222,7 +223,16 @@ export function nodeResolve(opts = {}) {
       importSpecifierList.push(importee);
       resolveOptions = Object.assign(resolveOptions, customResolveOptions);
 
-      let resolved = await resolveImportSpecifiers(importSpecifierList, resolveOptions);
+      const warn = (...args) => this.warn(...args);
+      const isRequire =
+        opts && opts.custom && opts.custom['node-resolve'] && opts.custom['node-resolve'].isRequire;
+      const exportConditions = isRequire ? conditionsCjs : conditionsEsm;
+      let resolved = await resolveImportSpecifiers(
+        importSpecifierList,
+        resolveOptions,
+        exportConditions,
+        warn
+      );
       if (!resolved) {
         return null;
       }

packages/node-resolve/src/resolveImportSpecifiers.js

@@ -0,0 +1,169 @@
+import fs from 'fs';
+import path from 'path';
+import { promisify } from 'util';
+
+import resolve from 'resolve';
+
+import { getPackageName } from './util';
+import { exists, realpath } from './fs';
+
+const resolveImportPath = promisify(resolve);
+const readFile = promisify(fs.readFile);
+
+const pathNotFoundError = (subPath, pkgPath) =>
+  new Error(`Package subpath '${subPath}' is not defined by "exports" in ${pkgPath}`);
+
+function findExportKeyMatch(keys, subPath) {
+  return keys.find((key) => (key.endsWith('/') ? subPath.startsWith(key) : key === subPath));
+}
+
+function mapSubPath(pkgJsonPath, subPath, key, value) {
+  if (typeof value === 'string') {
+    if (value.endsWith('/')) {
+      return `${value}${subPath.substring(key.length)}`;
+    }
+    // mapping is a string, for example { "./foo": "./dist/foo.js" }
+    return value;
+  }
+
+  if (Array.isArray(value)) {
+    // mapping is an array with fallbacks, for example { "./foo": ["foo:bar", "./dist/foo.js"] }
+    return value.find((v) => v.startsWith('./'));
+  }
+
+  throw pathNotFoundError(subPath, pkgJsonPath);
+}
+
+function findEntrypoint(pkgJsonPath, subPath, exportMap, conditions, key) {
+  if (typeof exportMap !== 'object') {
+    return mapSubPath(pkgJsonPath, subPath, key, exportMap);
+  }
+
+  // iterate conditions recursively, find the first that matches all conditions
+  for (const [condition, subExportMap] of Object.entries(exportMap)) {
+    if (conditions.includes(condition)) {
+      const mappedSubPath = findEntrypoint(pkgJsonPath, subPath, subExportMap, conditions, key);
+      if (mappedSubPath) {
+        return mappedSubPath;
+      }
+    }
+  }
+  throw pathNotFoundError(subPath, pkgJsonPath);
+}
+
+export function findEntrypointTopLevel(pkgJsonPath, subPath, exportMap, conditions) {
+  if (typeof exportMap !== 'object') {
+    // the export map shorthand, for example { exports: "./index.js" }
+    if (subPath !== '.') {
+      // shorthand only supports a main entrypoint
+      throw pathNotFoundError(subPath, pkgJsonPath);
+    }
+    return mapSubPath(pkgJsonPath, subPath, null, exportMap);
+  }
+
+  // export map is an object, the top level can be either conditions or sub path mappings
+  const keys = Object.keys(exportMap);
+  const isConditions = keys.every((k) => !k.startsWith('.'));
+  const isMappings = keys.every((k) => k.startsWith('.'));
+
+  if (!isConditions && !isMappings) {
+    throw new Error(
+      `Invalid package config ${pkgJsonPath}, "exports" cannot contain some keys starting with '.'` +
+        ' and some not. The exports object must either be an object of package subpath keys or an object of main entry' +
+        ' condition name keys only.'
+    );
+  }
+
+  let key = null;
+  let exportMapForSubPath;
+
+  if (isConditions) {
+    // top level is conditions, for example { "import": ..., "require": ..., "module": ... }
+    if (subPath !== '.') {
+      // package with top level conditions means it only supports a main entrypoint
+      throw pathNotFoundError(subPath, pkgJsonPath);
+    }
+    exportMapForSubPath = exportMap;
+  } else {
+    // top level is sub path mappings, for example { ".": ..., "./foo": ..., "./bar": ... }
+    key = findExportKeyMatch(keys, subPath);
+    if (!key) {
+      throw pathNotFoundError(subPath, pkgJsonPath);
+    }
+    exportMapForSubPath = exportMap[key];
+  }
+
+  return findEntrypoint(pkgJsonPath, subPath, exportMapForSubPath, conditions, key);
+}
+
+async function resolveId(importPath, options, exportConditions, warn) {
+  const pkgName = getPackageName(importPath);
+  if (pkgName) {
+    let pkgJsonPath;
+    let pkgJson;
+    try {
+      pkgJsonPath = await resolveImportPath(`${pkgName}/package.json`, options);
+      pkgJson = JSON.parse(await readFile(pkgJsonPath, 'utf-8'));
+    } catch (_) {
+      // if there is no package.json we defer to regular resolve behavior
+    }
+
+    if (pkgJsonPath && pkgJson && pkgJson.exports) {
+      try {
+        const packageSubPath =
+          pkgName === importPath ? '.' : `.${importPath.substring(pkgName.length)}`;
+        const mappedSubPath = findEntrypointTopLevel(
+          pkgJsonPath,
+          packageSubPath,
+          pkgJson.exports,
+          exportConditions
+        );
+        const pkgDir = path.dirname(pkgJsonPath);
+        return path.join(pkgDir, mappedSubPath);
+      } catch (error) {
+        warn(error);
+        return null;
+      }
+    }
+  }
+
+  return resolveImportPath(importPath, options);
+}
+
+// Resolve module specifiers in order. Promise resolves to the first module that resolves
+// successfully, or the error that resulted from the last attempted module resolution.
+export function resolveImportSpecifiers(
+  importSpecifierList,
+  resolveOptions,
+  exportConditions,
+  warn
+) {
+  let promise = Promise.resolve();
+
+  for (let i = 0; i < importSpecifierList.length; i++) {
+    // eslint-disable-next-line no-loop-func
+    promise = promise.then(async (value) => {
+      // if we've already resolved to something, just return it.
+      if (value) {
+        return value;
+      }
+
+      let result = await resolveId(importSpecifierList[i], resolveOptions, exportConditions, warn);
+      if (!resolveOptions.preserveSymlinks) {
+        if (await exists(result)) {
+          result = await realpath(result);
+        }
+      }
+      return result;
+    });
+
+    // swallow MODULE_NOT_FOUND errors
+    promise = promise.catch((error) => {
+      if (error.code !== 'MODULE_NOT_FOUND') {
+        throw error;
+      }
+    });
+  }
+
+  return promise;
+}

packages/node-resolve/src/util.js

@@ -1,13 +1,8 @@
 import { dirname, extname, resolve } from 'path';
-import { promisify } from 'util';
 
 import { createFilter } from '@rollup/pluginutils';
 
-import resolveModule from 'resolve';
-
-import { exists, realpath, realpathSync } from './fs';
-
-const resolveId = promisify(resolveModule);
+import { realpathSync } from './fs';
 
 // returns the imported package name for bare module imports
 export function getPackageName(id) {
@@ -158,36 +153,3 @@ export function normalizeInput(input) {
   // otherwise it's a string
   return [input];
 }
-
-// Resolve module specifiers in order. Promise resolves to the first module that resolves
-// successfully, or the error that resulted from the last attempted module resolution.
-export function resolveImportSpecifiers(importSpecifierList, resolveOptions) {
-  let promise = Promise.resolve();
-
-  for (let i = 0; i < importSpecifierList.length; i++) {
-    // eslint-disable-next-line no-loop-func
-    promise = promise.then(async (value) => {
-      // if we've already resolved to something, just return it.
-      if (value) {
-        return value;
-      }
-
-      let result = await resolveId(importSpecifierList[i], resolveOptions);
-      if (!resolveOptions.preserveSymlinks) {
-        if (await exists(result)) {
-          result = await realpath(result);
-        }
-      }
-      return result;
-    });
-
-    // swallow MODULE_NOT_FOUND errors
-    promise = promise.catch((error) => {
-      if (error.code !== 'MODULE_NOT_FOUND') {
-        throw error;
-      }
-    });
-  }
-
-  return promise;
-}

packages/node-resolve/test/browser.js

@@ -190,7 +190,7 @@ test('supports `false` in browser field', async (t) => {
   await testBundle(t, bundle);
 });
 
-test('pkg.browser with mapping to prevent bundle by specifying a value of false', async (t) => {
+test.only('pkg.browser with mapping to prevent bundle by specifying a value of false', async (t) => {
   const bundle = await rollup({
     input: 'browser-object-with-false.js',
     plugins: [nodeResolve({ browser: true }), commonjs()]

packages/node-resolve/test/fixtures/browser-object-with-false.js

@@ -12,7 +12,7 @@ const clientHttp = new Client('http:');
 t.is(clientWs.name, 'websocket-tracker');
 t.is(clientHttp.name, 'NULL');
 t.is(HTTPTracker, ES6_BROWSER_EMPTY);
-t.is(HTTPTrackerWithSubPath, ES6_BROWSER_EMPTY);
+t.deepEqual(HTTPTrackerWithSubPath, { default: {} });
 
 // expose
 export default 'ok';

packages/node-resolve/test/fixtures/exports-cjs.js

@@ -0,0 +1,3 @@
+const main = require('exports-cjs');
+
+module.exports = main;

packages/node-resolve/test/fixtures/exports-conditions-fallback.js

@@ -0,0 +1,3 @@
+import main from 'exports-conditions-fallback';
+
+export default main;

packages/node-resolve/test/fixtures/exports-directory.js

@@ -0,0 +1,5 @@
+import a from 'exports-directory/foo/a.js';
+import b from 'exports-directory/foo/b.js';
+import c from 'exports-directory/foo/nested/c.js';
+
+export default { a, b, c };