feat(node-resolve): support pkg imports and export array

Author: LarsDenBakker

packages/node-resolve/README.md

@@ -34,14 +34,18 @@ 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).
 
+## Package entrypoints
+
+This plugin supports the package entrypoints feature from node js, specified in the `exports` or `imports` field of a package. Check the [official documentation](https://nodejs.org/api/packages.html#packages_package_entry_points) for more information on how this works.
+
 ## Options
 
 ### `exportConditions`
@@ -62,6 +66,8 @@ 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`.
 
+> This option does not work when a package is using [package entrypoints](https://nodejs.org/api/packages.html#packages_package_entry_points)
+
 ### `moduleDirectories`
 
 Type: `Array[...String]`<br>
@@ -169,9 +175,9 @@ export default {
   output: {
     file: 'bundle.js',
     format: 'iife',
-    name: 'MyModule',
+    name: 'MyModule'
   },
-  plugins: [nodeResolve(), commonjs()],
+  plugins: [nodeResolve(), commonjs()]
 };
 ```
 
@@ -203,7 +209,7 @@ The node resolve plugin uses `import` by default, you can opt into using the `re
 ```js
 this.resolve(importee, importer, {
   skipSelf: true,
-  custom: { 'node-resolve': { isRequire: true } },
+  custom: { 'node-resolve': { isRequire: true } }
 });
 ```
 

packages/node-resolve/src/index.js

@@ -7,7 +7,7 @@ import isModule from 'is-module';
 
 import { isDirCached, isFileCached, readCachedFile } from './cache';
 import { exists, readFile, realpath } from './fs';
-import { resolveImportSpecifiers } from './resolveImportSpecifiers';
+import resolveImportSpecifiers from './resolveImportSpecifiers';
 import { getMainFields, getPackageName, normalizeInput } from './util';
 import handleDeprecatedOptions from './deprecated-options';
 

packages/node-resolve/src/package/resolvePackageExports.js

@@ -0,0 +1,48 @@
+import {
+  InvalidModuleSpecifierError,
+  InvalidConfigurationError,
+  isMappings,
+  isConditions,
+  isMixedExports
+} from './utils';
+import resolvePackageTarget from './resolvePackageTarget';
+import resolvePackageImportsExports from './resolvePackageImportsExports';
+
+async function resolvePackageExports(context, subpath, exports) {
+  if (isMixedExports(exports)) {
+    throw new InvalidConfigurationError(
+      context,
+      'All keys must either start with ./, or without one.'
+    );
+  }
+
+  if (subpath === '.') {
+    let mainExport;
+    // If exports is a String or Array, or an Object containing no keys starting with ".", then
+    if (typeof exports === 'string' || Array.isArray(exports) || isConditions(exports)) {
+      mainExport = exports;
+    } else if (isMappings(exports)) {
+      mainExport = exports['.'];
+    }
+
+    if (mainExport) {
+      const resolved = await resolvePackageTarget(context, { target: mainExport, subpath: '' });
+      if (resolved) {
+        return resolved;
+      }
+    }
+  } else if (isMappings(exports)) {
+    const resolvedMatch = await resolvePackageImportsExports(context, {
+      matchKey: subpath,
+      matchObj: exports
+    });
+
+    if (resolvedMatch) {
+      return resolvedMatch;
+    }
+  }
+
+  throw new InvalidModuleSpecifierError(context);
+}
+
+export default resolvePackageExports;

packages/node-resolve/src/package/resolvePackageImports.js

@@ -0,0 +1,49 @@
+import path from 'path';
+import fs from 'fs';
+import { pathToFileURL } from 'url';
+
+import { createBaseErrorMsg, InvalidModuleSpecifierError } from './utils';
+import resolvePackageImportsExports from './resolvePackageImportsExports';
+
+function findPackageJson(base) {
+  const { root } = path.parse(base);
+  let current = base;
+
+  while (current !== root && !current.endsWith('node_modules')) {
+    const pkgJsonPath = path.join(current, 'package.json');
+    if (fs.existsSync(pkgJsonPath)) {
+      const pkgJsonString = fs.readFileSync(pkgJsonPath, 'utf-8');
+      return { pkgJson: JSON.parse(pkgJsonString), pkgPath: current, pkgJsonPath };
+    }
+    current = path.resolve(current, '..');
+  }
+  return null;
+}
+
+function resolvePackageImports({ importSpecifier, importer, conditions, resolveId }) {
+  const result = findPackageJson(importer);
+  if (!result) {
+    throw new Error(createBaseErrorMsg('. Could not find a parent package.json.'));
+  }
+
+  const { pkgPath, pkgJsonPath, pkgJson } = result;
+  const pkgURL = pathToFileURL(`${pkgPath}/`);
+  const context = { importer, importSpecifier, pkgURL, pkgJsonPath, conditions, resolveId };
+
+  const { imports } = pkgJson;
+  if (!imports) {
+    throw new InvalidModuleSpecifierError(context, true);
+  }
+
+  if (importSpecifier === '#' || importSpecifier.startsWith('#/')) {
+    throw new InvalidModuleSpecifierError(context, 'Invalid import specifier.');
+  }
+
+  return resolvePackageImportsExports(context, {
+    matchKey: importSpecifier,
+    matchObj: imports,
+    internal: true
+  });
+}
+
+export default resolvePackageImports;

packages/node-resolve/src/package/resolvePackageImportsExports.js

@@ -0,0 +1,44 @@
+/* eslint-disable no-await-in-loop */
+import resolvePackageTarget from './resolvePackageTarget';
+
+import { InvalidModuleSpecifierError } from './utils';
+
+async function resolvePackageImportsExports(context, { matchKey, matchObj, internal }) {
+  if (!matchKey.endsWith('*') && matchKey in matchObj) {
+    const target = matchObj[matchKey];
+    const resolved = await resolvePackageTarget(context, { target, subpath: '', internal });
+    return resolved;
+  }
+
+  const expansionKeys = Object.keys(matchObj)
+    .filter((k) => k.endsWith('/') || k.endsWith('*'))
+    .sort((a, b) => b.length - a.length);
+
+  for (const expansionKey of expansionKeys) {
+    const prefix = expansionKey.substring(0, expansionKey.length - 1);
+
+    if (expansionKey.endsWith('*') && matchKey.startsWith(prefix)) {
+      const target = matchObj[expansionKey];
+      const subpath = matchKey.substring(expansionKey.length - 1);
+      const resolved = await resolvePackageTarget(context, {
+        target,
+        subpath,
+        pattern: true,
+        internal
+      });
+      return resolved;
+    }
+
+    if (matchKey.startsWith(expansionKey)) {
+      const target = matchObj[expansionKey];
+      const subpath = matchKey.substring(expansionKey.length);
+
+      const resolved = await resolvePackageTarget(context, { target, subpath, internal });
+      return resolved;
+    }
+  }
+
+  throw new InvalidModuleSpecifierError(context, internal);
+}
+
+export default resolvePackageImportsExports;

packages/node-resolve/src/package/resolvePackageTarget.js

@@ -0,0 +1,111 @@
+/* eslint-disable no-await-in-loop */
+import { pathToFileURL } from 'url';
+
+import { isUrl, InvalidModuleSpecifierError, InvalidPackageTargetError } from './utils';
+
+function includesInvalidSegments(pathSegments) {
+  return pathSegments
+    .split('/')
+    .slice(1)
+    .some((t) => ['.', '..', 'node_modules'].includes(t));
+}
+
+async function resolvePackageTarget(context, { target, subpath, pattern, internal }) {
+  if (target == null) {
+    return null;
+  }
+
+  if (typeof target === 'string') {
+    if (!pattern && subpath.length > 0 && !target.endsWith('/')) {
+      throw new InvalidModuleSpecifierError(context);
+    }
+
+    if (!target.startsWith('./')) {
+      if (internal && !['/', '../'].some((p) => target.startsWith(p)) && !isUrl(target)) {
+        // this is a bare package import, remap it and resolve it using regular node resolve
+        if (pattern) {
+          const result = await context.resolveId(
+            target.replace(/\*/g, subpath),
+            context.pkgURL.href
+          );
+          return result ? pathToFileURL(result.location) : null;
+        }
+
+        const result = await context.resolveId(`${target}${subpath}`, context.pkgURL.href);
+        return result ? pathToFileURL(result.location) : null;
+      }
+      throw new InvalidPackageTargetError(context, `Invalid mapping: "${target}".`);
+    }
+
+    if (includesInvalidSegments(target)) {
+      throw new InvalidPackageTargetError(context, `Invalid mapping: "${target}".`);
+    }
+
+    const resolvedTarget = new URL(target, context.pkgURL);
+    if (!resolvedTarget.href.startsWith(context.pkgURL.href)) {
+      throw new InvalidPackageTargetError(
+        context,
+        `Resolved to ${resolvedTarget.href} which is outside package ${context.pkgURL.href}`
+      );
+    }
+
+    if (includesInvalidSegments(subpath)) {
+      throw new InvalidModuleSpecifierError(context);
+    }
+
+    if (pattern) {
+      return resolvedTarget.href.replace(/\*/g, subpath);
+    }
+    return new URL(subpath, resolvedTarget).href;
+  }
+
+  if (Array.isArray(target)) {
+    let lastError;
+    for (const item of target) {
+      try {
+        const resolved = await resolvePackageTarget(context, {
+          target: item,
+          subpath,
+          pattern,
+          internal
+        });
+
+        if (resolved) {
+          return resolved;
+        }
+      } catch (error) {
+        if (!(error instanceof InvalidPackageTargetError)) {
+          throw error;
+        } else {
+          lastError = error;
+        }
+      }
+    }
+
+    if (lastError) {
+      throw lastError;
+    }
+    return null;
+  }
+
+  if (typeof target === 'object') {
+    for (const [key, value] of Object.entries(target)) {
+      if (key === 'default' || context.conditions.includes(key)) {
+        const resolved = await resolvePackageTarget(context, {
+          target: value,
+          subpath,
+          pattern,
+          internal
+        });
+
+        if (resolved) {
+          return resolved;
+        }
+      }
+    }
+  }
+
+  throw new InvalidPackageTargetError(context, `Invalid exports field.`);
+}
+
+export default resolvePackageTarget;

packages/node-resolve/src/package/utils.js

@@ -0,0 +1,51 @@
+export function isUrl(str) {
+  try {
+    return !!new URL(str);
+  } catch (_) {
+    return false;
+  }
+}
+
+export function isConditions(exports) {
+  return typeof exports === 'object' && Object.keys(exports).every((k) => !k.startsWith('.'));
+}
+
+export function isMappings(exports) {
+  return typeof exports === 'object' && !isConditions(exports);
+}
+
+export function isMixedExports(exports) {
+  const keys = Object.keys(exports);
+  return keys.some((k) => k.startsWith('.')) && keys.some((k) => !k.startsWith('.'));
+}
+
+export function createBaseErrorMsg(importSpecifier, importer) {
+  return `Could not resolve import "${importSpecifier}" in ${importer}`;
+}
+
+export function createErrorMsg(context, reason, internal) {
+  const { importSpecifier, importer, pkgJsonPath } = context;
+  const base = createBaseErrorMsg(importSpecifier, importer);
+  const field = internal ? 'imports' : 'exports';
+  return `${base} using ${field} defined in ${pkgJsonPath}.${reason ? ` ${reason}` : ''}`;
+}
+
+export class ResolveError extends Error {}
+
+export class InvalidConfigurationError extends ResolveError {
+  constructor(context, reason) {
+    super(createErrorMsg(context, `Invalid "exports" field. ${reason}`));
+  }
+}
+
+export class InvalidModuleSpecifierError extends ResolveError {
+  constructor(context, internal) {
+    super(createErrorMsg(context, internal));
+  }
+}
+
+export class InvalidPackageTargetError extends ResolveError {
+  constructor(context, reason) {
+    super(createErrorMsg(context, reason));
+  }
+}