test(transformer): update fixtures script support overrides (#7688)

Support overriding test fixtures in `update_fixtures.js` script.

Any files in `tasks/transform_conformance/overrides` are copied into Babel test fixtures. If `options.json` is overridden, then script runs Babel with updated options, to generate a new `output` file for the fixture.

tasks/transform_conformance/update_fixtures.js

@@ -13,8 +13,9 @@
 //    (or maybe don't - what does this option mean?)
 
 import { transformFileAsync } from '@babel/core';
-import { readdir, readFile, rename, writeFile } from 'fs/promises';
-import { join as pathJoin } from 'path';
+import assert from 'assert';
+import { copyFile, readdir, readFile, rename, writeFile } from 'fs/promises';
+import { extname, join as pathJoin } from 'path';
 
 const PACKAGES = ['babel-plugin-transform-class-properties'];
 const FILTER_OUT_PRESETS = ['env'];
@@ -25,6 +26,7 @@ const FILTER_OUT_PLUGINS = [
 ];
 
 const PACKAGES_PATH = pathJoin(import.meta.dirname, '../coverage/babel/packages');
+const OVERRIDES_PATH = pathJoin(import.meta.dirname, 'overrides');
 
 // Copied from `@babel/helper-transform-fixture-test-runner`
 const EXTERNAL_HELPERS_VERSION = '7.100.0';
@@ -45,41 +47,83 @@ async function updateDir(dirPath, options, hasChangedOptions) {
   const files = await readdir(dirPath, { withFileTypes: true });
 
   const dirFiles = [];
-  let optionsFile, inputFile, outputFile;
+
+  const filenames = { options: null, input: null, output: null, exec: null };
+  const overrides = { options: false, input: false, output: false, exec: false };
+
+  // Find files in dir
   for (const file of files) {
+    const filename = file.name;
     if (file.isDirectory()) {
-      dirFiles.push(file);
-    } else if (file.name === 'options.json') {
-      optionsFile = file;
-    } else if (file.name.startsWith('output.')) {
-      outputFile = file;
-    } else if (file.name.startsWith('input.')) {
-      inputFile = file;
+      dirFiles.push(filename);
+    } else {
+      const ext = extname(filename),
+        type = ext === '' ? filename : filename.slice(0, -ext.length);
+      if (Object.hasOwn(filenames, type)) filenames[type] = filename;
+    }
+  }
+
+  // Find override files
+  const overridesDirPath = pathJoin(`${OVERRIDES_PATH}${dirPath.slice(PACKAGES_PATH.length)}`);
+  let overrideFiles;
+  try {
+    overrideFiles = await readdir(overridesDirPath, { withFileTypes: true });
+  } catch (err) {
+    if (err?.code !== 'ENOENT') throw err;
+  }
+
+  if (overrideFiles) {
+    for (const file of overrideFiles) {
+      if (file.isDirectory()) continue;
+
+      const filename = file.name;
+      // `reason.txt` files are to document why override is used
+      if (filename === 'reason.txt') continue;
+
+      const ext = extname(filename),
+        type = filename.slice(0, -ext.length),
+        path = pathJoin(overridesDirPath, filename);
+
+      assert(Object.hasOwn(overrides, type), `Unexpected override file: ${path}`);
+
+      const originalPath = pathJoin(dirPath, filename);
+      if (filenames[type]) {
+        const originalFilename = filenames[type];
+        assert(originalFilename === filename, `Unmatched override file: ${path} (original: ${originalFilename})`);
+        await backupFile(originalPath);
+      }
+
+      filenames[type] = filename;
+      overrides[type] = true;
+      if (type === 'options') hasChangedOptions = true;
+
+      await copyFile(path, originalPath);
     }
   }
 
-  if (optionsFile) {
-    const path = pathJoin(dirPath, optionsFile.name);
+  // Update options, save to file, and merge options with parent
+  if (filenames.options) {
+    const path = pathJoin(dirPath, filenames.options);
     const localOptions = JSON.parse(await readFile(path, 'utf8'));
-    if (updateOptions(localOptions)) {
+    if (!overrides.options && updateOptions(localOptions)) {
       hasChangedOptions = true;
-      const backupPath = pathJoin(dirPath, 'options.original.json');
-      await rename(path, backupPath);
+      await backupFile(path);
       await writeFile(path, JSON.stringify(localOptions, null, 2) + '\n');
     }
     options = mergeOptions(options, localOptions);
   }
 
-  if (outputFile && hasChangedOptions) {
-    const inputPath = pathJoin(dirPath, inputFile.name);
-    const outputPath = pathJoin(dirPath, outputFile.name);
-    const backupOutputPath = pathJoin(dirPath, `output.original.${outputFile.name.slice(7)}`);
-    await rename(outputPath, backupOutputPath);
+  // Run Babel with updated options/input
+  if (filenames.output && (hasChangedOptions || overrides.input) && !overrides.output) {
+    const inputPath = pathJoin(dirPath, filenames.input),
+      outputPath = pathJoin(dirPath, filenames.output);
+    await backupFile(outputPath);
     await transform(inputPath, outputPath, options);
   }
 
-  for (const file of dirFiles) {
-    const path = pathJoin(dirPath, file.name);
+  // Process subfolders
+  for (const filename of dirFiles) {
+    const path = pathJoin(dirPath, filename);
     await updateDir(path, options, hasChangedOptions);
   }
 }
@@ -211,3 +255,14 @@ function getName(stringOrArray) {
   if (Array.isArray(stringOrArray)) return stringOrArray[0];
   return stringOrArray;
 }
+
+/**
+ * Backup file.
+ * @param {string} path - Original path
+ * @returns {undefined}
+ */
+async function backupFile(path) {
+  const ext = extname(path),
+    backupPath = `${path.slice(0, -ext.length)}.original${ext}`;
+  await rename(path, backupPath);
+}