test: cover docusaurus.config.ts markdown preprocessor

lib/docusaurusConfigPreprocessor.test.mts

@@ -0,0 +1,41 @@
+import { registerHooks } from 'node:module';
+import path from 'node:path';
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { resolve } from './testHelpers/resolveExtensionlessTs.mjs';
+
+// docusaurus.config.ts imports its ./lib/* helpers without file extensions,
+// which only Docusaurus's own webpack bundler resolves. Register a
+// test-only hook (see testHelpers/resolveExtensionlessTs.mjs) so this file
+// can import the real docusaurus.config.ts directly, instead of duplicating
+// its markdown.preprocessor logic.
+registerHooks({ resolve });
+
+const { default: config } = await import('../docusaurus.config.ts');
+const { preprocessor } = config.markdown;
+const importedReadmePath = path.resolve('README.md');
+
+test('markdown.preprocessor (root README.md import)', async (t) => {
+  await t.test('strips .md from /docs and /analyses links', () => {
+    const result = preprocessor({
+      fileContent:
+        'See [docs](/docs/foo.md) and [analyses](/analyses/bar.md#section).',
+      filePath: importedReadmePath,
+    });
+
+    assert.equal(
+      result,
+      'See [docs](/docs/foo/) and [analyses](/analyses/bar/#section).',
+    );
+  });
+
+  await t.test('leaves non-README imports untouched', () => {
+    const fileContent = 'See [docs](/docs/foo.md).';
+    const result = preprocessor({
+      fileContent,
+      filePath: path.resolve('docs/other.md'),
+    });
+
+    assert.equal(result, fileContent);
+  });
+});

lib/testHelpers/resolveExtensionlessTs.mjs

@@ -0,0 +1,34 @@
+// Minimal Node.js module-resolution hook used only by tests.
+//
+// docusaurus.config.ts imports its ./lib/* helpers without file extensions
+// (e.g. `./lib/getBuildContext`), which Docusaurus's own webpack bundler
+// resolves fine but Node's native ESM loader does not. This hook teaches
+// Node to fall back to `<specifier>.ts` (and `<specifier>/index.ts` for
+// directory imports) so docusaurus.config.ts can be imported directly in
+// `node --test`, without changing any production import statement.
+import { existsSync, statSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+
+export function resolve(specifier, context, nextResolve) {
+  try {
+    return nextResolve(specifier, context);
+  } catch (err) {
+    if (!specifier.startsWith('.')) throw err;
+
+    if (err.code === 'ERR_MODULE_NOT_FOUND') {
+      const candidate = new URL(specifier + '.ts', context.parentURL);
+      if (existsSync(fileURLToPath(candidate))) {
+        return nextResolve(specifier + '.ts', context);
+      }
+    }
+
+    if (err.code === 'ERR_UNSUPPORTED_DIR_IMPORT') {
+      const dirPath = fileURLToPath(new URL(specifier, context.parentURL));
+      if (existsSync(dirPath) && statSync(dirPath).isDirectory()) {
+        return nextResolve(specifier + '/index.ts', context);
+      }
+    }
+
+    throw err;
+  }
+}

package.json

@@ -36,7 +36,7 @@
     "precheck:links": "npm run build",
     "seq": "bash -c 'for cmd in \"$@\"; do npm run $cmd || exit 1; done' - ",
     "serve": "npm run docus:serve",
-    "test:coverage": "c8 --reporter=text --reporter=lcov --check-coverage --lines 99 --statements 99 --branches 97 --functions 100 npm run test:unit",
+    "test:coverage": "c8 --reporter=text --reporter=lcov --exclude 'docusaurus.config.ts' --exclude 'lib/testHelpers/**' --check-coverage --lines 99 --statements 99 --branches 97 --functions 100 npm run test:unit",
     "test:unit": "node --experimental-strip-types --experimental-test-module-mocks --test 'lib/**/*.test.mts' 'scripts/**/*.test.mjs'",
     "test": "npm run check && npm run test:unit",
     "typecheck": "tsc",