feat(node-resolve): add support for self-package imports

Author: LarsDenBakker

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

@@ -1,33 +1,8 @@
-/* eslint-disable no-await-in-loop */
-import path from 'path';
-import fs from 'fs';
 import { pathToFileURL } from 'url';
-import { promisify } from 'util';
 
-import { createBaseErrorMsg, InvalidModuleSpecifierError } from './utils';
+import { createBaseErrorMsg, findPackageJson, InvalidModuleSpecifierError } from './utils';
 import resolvePackageImportsExports from './resolvePackageImportsExports';
 
-const fileExists = promisify(fs.exists);
-
-function isModuleDir(current, moduleDirs) {
-  return moduleDirs.some((dir) => current.endsWith(dir));
-}
-
-async function findPackageJson(base, moduleDirs) {
-  const { root } = path.parse(base);
-  let current = base;
-
-  while (current !== root && !isModuleDir(current, moduleDirs)) {
-    const pkgJsonPath = path.join(current, 'package.json');
-    if (await fileExists(pkgJsonPath)) {
-      const pkgJsonString = fs.readFileSync(pkgJsonPath, 'utf-8');
-      return { pkgJson: JSON.parse(pkgJsonString), pkgPath: current, pkgJsonPath };
-    }
-    current = path.resolve(current, '..');
-  }
-  return null;
-}
-
 async function resolvePackageImports({
   importSpecifier,
   importer,

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

@@ -1,3 +1,29 @@
+/* eslint-disable no-await-in-loop */
+import path from 'path';
+import fs from 'fs';
+import { promisify } from 'util';
+
+const fileExists = promisify(fs.exists);
+
+function isModuleDir(current, moduleDirs) {
+  return moduleDirs.some((dir) => current.endsWith(dir));
+}
+
+export async function findPackageJson(base, moduleDirs) {
+  const { root } = path.parse(base);
+  let current = base;
+
+  while (current !== root && !isModuleDir(current, moduleDirs)) {
+    const pkgJsonPath = path.join(current, 'package.json');
+    if (await fileExists(pkgJsonPath)) {
+      const pkgJsonString = fs.readFileSync(pkgJsonPath, 'utf-8');
+      return { pkgJson: JSON.parse(pkgJsonString), pkgPath: current, pkgJsonPath };
+    }
+    current = path.resolve(current, '..');
+  }
+  return null;
+}
+
 export function isUrl(str) {
   try {
     return !!new URL(str);

packages/node-resolve/src/resolveImportSpecifiers.js

@@ -9,11 +9,29 @@ import { exists, realpath } from './fs';
 import { isDirCached, isFileCached, readCachedFile } from './cache';
 import resolvePackageExports from './package/resolvePackageExports';
 import resolvePackageImports from './package/resolvePackageImports';
-import { ResolveError } from './package/utils';
+import { findPackageJson, ResolveError } from './package/utils';
 
 const resolveImportPath = promisify(resolve);
 const readFile = promisify(fs.readFile);
 
+async function getPackageJson(importer, pkgName, resolveOptions, moduleDirectories) {
+  if (importer) {
+    const selfPackageJsonResult = await findPackageJson(importer, moduleDirectories);
+    if (selfPackageJsonResult && selfPackageJsonResult.pkgJson.name === pkgName) {
+      // the referenced package name is the current package
+      return selfPackageJsonResult;
+    }
+  }
+
+  try {
+    const pkgJsonPath = await resolveImportPath(`${pkgName}/package.json`, resolveOptions);
+    const pkgJson = JSON.parse(await readFile(pkgJsonPath, 'utf-8'));
+    return { pkgJsonPath, pkgJson };
+  } catch (_) {
+    return null;
+  }
+}
+
 async function resolveId({
   importer,
   importSpecifier,
@@ -88,22 +106,17 @@ async function resolveId({
     });
     location = fileURLToPath(resolveResult);
   } else if (pkgName) {
-    // this is a bare import, resolve using package exports if possible
-    let pkgJsonPath;
-    let pkgJson;
-    try {
-      pkgJsonPath = await resolveImportPath(`${pkgName}/package.json`, resolveOptions);
-      pkgJson = JSON.parse(await readFile(pkgJsonPath, 'utf-8'));
-    } catch (_) {
-      // if there is no package.json we defer to regular resolve behavior
-    }
+    // it's a bare import, find the package.json and resolve using package exports if available
+    const result = await getPackageJson(importer, pkgName, resolveOptions, moduleDirectories);
 
-    if (pkgJsonPath && pkgJson && pkgJson.exports) {
+    if (result && result.pkgJson.exports) {
+      const { pkgJson, pkgJsonPath } = result;
       try {
         const subpath =
           pkgName === importSpecifier ? '.' : `.${importSpecifier.substring(pkgName.length)}`;
         const pkgDr = pkgJsonPath.replace('package.json', '');
         const pkgURL = pathToFileURL(pkgDr);
+
         const context = {
           importer,
           importSpecifier,

packages/node-resolve/test/fixtures/node_modules/self-package-import/foo/a.js

@@ -0,0 +1,3 @@
+import selfPkgImport from 'self-package-import/a';
+
+export default selfPkgImport;

packages/node-resolve/test/fixtures/node_modules/self-package-import/foo/b.js

@@ -349,3 +349,19 @@ test('can override a star pattern using null', async (t) => {
 
   t.true(errors[0].message.includes('Could not resolve import "exports-null-override/foo/a" in '));
 });
+
+test('can self-import a package when using exports field', async (t) => {
+  const bundle = await rollup({
+    input: 'self-package-import',
+    onwarn: () => {
+      t.fail('No warnings were expected');
+    },
+    plugins: [nodeResolve()]
+  });
+  const { module } = await testBundle(t, bundle);
+
+  t.deepEqual(module.exports, {
+    a: 'a',
+    b: 'b'
+  });
+});