Support importing local .json files in ImportResolver (#288)

src/resolver.ts

@@ -549,6 +549,9 @@ export class ImportResolver {
       if (normalizedResolvedPath.endsWith('.css')) {
         return this._loadLocalStyle(resolvedPath, content);
       }
+      if (normalizedResolvedPath.endsWith('.json')) {
+        return this._loadLocalJson(resolvedPath, content);
+      }
 
       return await this._options.dynamicLoader(content);
     }
@@ -571,15 +574,36 @@ export class ImportResolver {
       candidates.add(`${baseCandidate}.tsx`);
       candidates.add(`${baseCandidate}.js`);
       candidates.add(`${baseCandidate}.css`);
+      candidates.add(`${baseCandidate}.json`);
       candidates.add(PathExt.join(baseCandidate, 'index.ts'));
       candidates.add(PathExt.join(baseCandidate, 'index.tsx'));
       candidates.add(PathExt.join(baseCandidate, 'index.js'));
       candidates.add(PathExt.join(baseCandidate, 'index.css'));
+      candidates.add(PathExt.join(baseCandidate, 'index.json'));
     }
 
     return Array.from(candidates);
   }
 
+  private _loadLocalJson(path: string, content: string): IModule {
+    let parsed: unknown;
+    try {
+      parsed = JSON.parse(content);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      throw new Error(`Invalid JSON file "${path}": ${message}`);
+    }
+
+    const jsonModule: Record<string, unknown> = {
+      __esModule: true,
+      default: parsed
+    };
+    if (parsed && typeof parsed === 'object' && !Array.isArray(parsed)) {
+      Object.assign(jsonModule, parsed);
+    }
+    return jsonModule as unknown as IModule;
+  }
+
   private _loadLocalStyle(path: string, css: string): IModule {
     this._snapshotLocalStyle(path);
     this._loadedLocalStylePaths.add(path);

ui-tests/tests/plugin-playground.spec.ts

@@ -57,6 +57,8 @@ const CSS_IMPORT_TEST_MARKER_ID = 'playground-css-import-test-marker';
 const CSS_IMPORT_TEST_COLOR = 'rgb(17, 34, 51)';
 const CSS_IMPORT_TEST_UPDATED_COLOR = 'rgb(34, 68, 102)';
 const CSS_IMPORT_TEST_BROKEN_MODULE_ERROR = 'css import rollback test failure';
+const JSON_IMPORT_TEST_PLUGIN_ID = 'playground-json-import-test:plugin';
+const JSON_IMPORT_TEST_MARKER_ID = 'playground-json-import-test-marker';
 const COMMAND_COMPLETION_FILE = 'command-completion.ts';
 const INVOKE_FILE_COMPLETER_COMMAND = 'completer:invoke-file';
 const JUPYTERLITE_AI_OPEN_OR_REVEAL_CHAT_COMMAND =
@@ -248,6 +250,39 @@ const CSS_IMPORT_TEST_PACKAGE_JSON_WITH_STYLE = JSON.stringify(
   2
 );
 
+const JSON_IMPORT_TEST_DATA = JSON.stringify(
+  {
+    greeting: 'Hello from local JSON',
+    version: '1.2.3'
+  },
+  null,
+  2
+);
+const JSON_IMPORT_TEST_SOURCE = `import { JupyterFrontEnd, JupyterFrontEndPlugin } from '@jupyterlab/application';
+import config, { version } from './config.json';
+
+const plugin: JupyterFrontEndPlugin<void> = {
+  id: '${JSON_IMPORT_TEST_PLUGIN_ID}',
+  autoStart: true,
+  activate: (app: JupyterFrontEnd) => {
+    const existing = document.getElementById('${JSON_IMPORT_TEST_MARKER_ID}');
+    if (existing) {
+      existing.remove();
+    }
+    const marker = document.createElement('div');
+    marker.id = '${JSON_IMPORT_TEST_MARKER_ID}';
+    marker.dataset.greeting = String(config.greeting || '');
+    marker.dataset.version = String(version || '');
+    document.body.appendChild(marker);
+  },
+  deactivate: () => {
+    document.getElementById('${JSON_IMPORT_TEST_MARKER_ID}')?.remove();
+  }
+};
+
+export default plugin;
+`;
+
 const DYNAMIC_SETTINGS_PERSIST_TEST_PLUGIN_ID =
   'dynamic-settings-persist-test:plugin';
 const DYNAMIC_SETTINGS_PERSIST_TEST_SET_COMMAND =
@@ -1929,6 +1964,55 @@ test('rolls back CSS changes when plugin schema parsing fails', async ({
   ).resolves.toBe(CSS_IMPORT_TEST_COLOR);
 });
 
+test('loads plugin importing local .json file', async ({ page, tmpPath }) => {
+  const projectRoot = `${tmpPath}/json-import-test`;
+  const sourcePath = `${projectRoot}/index.ts`;
+  const jsonPath = `${projectRoot}/config.json`;
+
+  await page.contents.uploadContent(JSON_IMPORT_TEST_DATA, 'text', jsonPath);
+  await page.contents.uploadContent(
+    JSON_IMPORT_TEST_SOURCE,
+    'text',
+    sourcePath
+  );
+  await page.goto();
+
+  await page.filebrowser.open(sourcePath);
+  expect(await page.activity.activateTab('index.ts')).toBe(true);
+
+  await page.waitForCondition(() =>
+    page.evaluate((id: string) => {
+      return window.jupyterapp.commands.hasCommand(id);
+    }, LOAD_COMMAND)
+  );
+  const loadResult = await page.evaluate((id: string) => {
+    return window.jupyterapp.commands.execute(id);
+  }, LOAD_COMMAND);
+  expect(loadResult.ok).toBe(true);
+  expect(loadResult.status).toBe('loaded');
+  expect(loadResult.pluginIds).toContain(JSON_IMPORT_TEST_PLUGIN_ID);
+
+  await page.waitForCondition(() =>
+    page.evaluate(
+      ({ markerId, greeting, version }) => {
+        const marker = document.getElementById(markerId);
+        if (!marker) {
+          return false;
+        }
+        return (
+          marker.dataset.greeting === greeting &&
+          marker.dataset.version === version
+        );
+      },
+      {
+        markerId: JSON_IMPORT_TEST_MARKER_ID,
+        greeting: 'Hello from local JSON',
+        version: '1.2.3'
+      }
+    )
+  );
+});
+
 test('persists dynamic plugin settings in browser storage', async ({
   page,
   tmpPath