Support custom loaders in ESM format

.github/workflows/tests.yml

@@ -110,6 +110,9 @@ jobs:
           timeout_minutes: 10
           max_attempts: 5
           command: yarn test:leaks --ci
+      - name: Tests using Node.js runner
+        if: ${{ matrix.node-version >= 22 }}
+        run: yarn test:node
 
   trackback:
     name: trackback rc dependencies
@@ -158,7 +161,7 @@ jobs:
         with:
           timeout_minutes: 10
           max_attempts: 5
-          command: TEST_BROWSER=true yarn jest --no-watchman --ci browser  
+          command: TEST_BROWSER=true yarn jest --no-watchman --ci browser
   analyze:
     name: Analyze
     runs-on: ubuntu-latest

package.json

@@ -43,6 +43,7 @@
     "test": "jest --no-watchman",
     "test-fed-compat": "ts-node --transpileOnly --compiler-options='{\"module\":\"commonjs\"}' scripts/fetch-federation-tests && yarn test federation-compat",
     "test:leaks": "cross-env \"LEAK_TEST=1\" jest --no-watchman --detectOpenHandles --detectLeaks --logHeapUsage",
+    "test:node": "node --experimental-strip-types --test **/tests/**/*.node.*s",
     "ts:check": "tsc --noEmit"
   },
   "devDependencies": {

packages/load/src/utils/custom-loader.ts

@@ -1,20 +1,32 @@
 import { createRequire } from 'module';
-import { join as joinPaths } from 'path';
+import { isAbsolute, join as joinPaths } from 'path';
 
-export function getCustomLoaderByPath(path: string, cwd: string) {
+function extractLoaderFromModule(loaderModule: any) {
+  if (loaderModule) {
+    if (loaderModule.default && typeof loaderModule.default === 'function') {
+      return loaderModule.default;
+    }
+    if (typeof loaderModule === 'function') {
+      return loaderModule;
+    }
+  }
+}
+
+export async function getCustomLoaderByPath(path: string, cwd: string) {
   try {
-    const requireFn = createRequire(joinPaths(cwd, 'noop.js'));
-    const requiredModule = requireFn(path);
+    const absolutePath = isAbsolute(path) ? path : joinPaths(cwd, path);
+    const importedModule = await import(absolutePath);
+    return extractLoaderFromModule(importedModule);
+  } catch (e: any) {}
 
-    if (requiredModule) {
-      if (requiredModule.default && typeof requiredModule.default === 'function') {
-        return requiredModule.default;
-      }
+  return null;
+}
 
-      if (typeof requiredModule === 'function') {
-        return requiredModule;
-      }
-    }
+function getCustomLoaderByPathSync(path: string, cwd: string) {
+  try {
+    const requireFn = createRequire(joinPaths(cwd, 'noop.js'));
+    const requiredModule = requireFn(path);
+    return extractLoaderFromModule(requiredModule);
   } catch (e: any) {}
 
   return null;
@@ -40,7 +52,7 @@ export function useCustomLoaderSync(loaderPointer: any, cwd: string) {
   let loader;
 
   if (typeof loaderPointer === 'string') {
-    loader = getCustomLoaderByPath(loaderPointer, cwd);
+    loader = getCustomLoaderByPathSync(loaderPointer, cwd);
   } else if (typeof loaderPointer === 'function') {
     loader = loaderPointer;
   }

packages/load/tests/custom-loader.mjs

@@ -0,0 +1,20 @@
+import { buildSchema, parse } from 'graphql';
+
+const loader = function (_, { customLoaderContext: { loaderType }, fooFieldName }) {
+  if (loaderType === 'documents') {
+    return parse(/* GraphQL */ `
+      query TestQuery {
+        ${fooFieldName}
+      }
+    `);
+  } else if (loaderType === 'schema') {
+    return buildSchema(/* GraphQL */ `
+      type Query {
+        ${fooFieldName}: String
+      }
+    `);
+  }
+  return 'I like turtles';
+};
+
+export default loader;

packages/load/tests/loaders/documents/documents-from-glob.spec.ts

@@ -171,7 +171,7 @@ describe('documentsFromGlob', () => {
         loaderType: 'documents',
       };
       const pointerOptions = {
-        loader: join(__dirname, '../../custom-loader.js'),
+        loader: join(__dirname, '../../custom-loader.cjs'),
         fooFieldName: 'myFooField',
       };
       const result = await load(

packages/load/tests/loaders/schema/integration.spec.ts

@@ -150,7 +150,7 @@ describe('loadSchema', () => {
         loaderType: 'schema',
       };
       const pointerOptions = {
-        loader: join(__dirname, '../../custom-loader.js'),
+        loader: join(__dirname, '../../custom-loader.cjs'),
         fooFieldName: 'myFooField',
       };
       const result = await load(

packages/load/tests/use-custom-loader.node.mjs

@@ -0,0 +1,26 @@
+import assert from 'node:assert';
+import { describe, it } from 'node:test';
+import { versionInfo as graphqlVersionInfo } from 'graphql';
+import { useCustomLoader, useCustomLoaderSync } from '../src/utils/custom-loader.ts';
+
+describe('useCustomLoader', () => {
+  const skipCjsTests = graphqlVersionInfo.major >= 17;
+
+  it('can load a custom cjs loader from a file path', { skip: skipCjsTests }, async () => {
+    const loader = await useCustomLoader(`./custom-loader.cjs`, import.meta.dirname);
+    const result = await loader('some-name', { customLoaderContext: {} });
+    assert.strictEqual(result, 'I like turtles');
+  });
+
+  it('can load a custom cjs loader synchronously', { skip: skipCjsTests }, async () => {
+    const loader = useCustomLoaderSync(`./custom-loader.cjs`, import.meta.dirname);
+    const result = await loader('some-name', { customLoaderContext: {} });
+    assert.strictEqual(result, 'I like turtles');
+  });
+
+  it('can load a custom mjs loader from a file path', async () => {
+    const loader = await useCustomLoader(`./custom-loader.mjs`, import.meta.dirname);
+    const result = await loader('some-name', { customLoaderContext: {} });
+    assert.strictEqual(result, 'I like turtles');
+  });
+});

packages/load/tests/use-custom-loader.spec.ts

@@ -2,7 +2,7 @@ import { getCustomLoaderByPath } from '../src/utils/custom-loader.js';
 
 describe('getCustomLoaderByPath', () => {
   it('can load a custom loader from a file path', async () => {
-    const loader = getCustomLoaderByPath('./custom-loader.js', __dirname);
+    const loader = await getCustomLoaderByPath('./custom-loader.cjs', __dirname);
     expect(loader).toBeDefined();
     expect(loader('some-name', { customLoaderContext: {} })).toEqual('I like turtles');
   });