Add a script to migrate to BCD tags

scripts/migrate.ts

@@ -0,0 +1,80 @@
+import assert from 'assert';
+import fs from 'fs';
+import path from 'path';
+import { fdir } from 'fdir';
+import { features } from '../index.js';
+
+const BCD_PATH = '/Users/foolip/mdn/browser-compat-data';
+
+// Map from api.CoolThing.something to cool-thing
+const bcdToFeature = new Map();
+
+// Set of the first part of the BCD path encountered.
+const bcdDirs = new Set();
+
+for (const [feature, {compat_features}] of Object.entries(features)) {
+    if (!compat_features) {
+        continue;
+    }
+    for (const key of compat_features) {
+        assert(!bcdToFeature.has(key), `${key} is used in compat_features twice`);
+        bcdToFeature.set(key, feature);
+        bcdDirs.add(key.split('.')[0]);
+    }
+}
+
+const bcdJsons = new fdir()
+    .withBasePath()
+    .filter((fp) => {
+        const dir = path.relative(BCD_PATH, fp).split(path.sep)[0];
+        return bcdDirs.has(dir);
+    })
+    .filter((fp) => fp.endsWith('.json'))
+    .crawl(BCD_PATH)
+    .sync();
+
+const lookup = (root, key) => {
+    const parts = key.split('.');
+    let node = root;
+    for (const part of parts) {
+        if (Object.hasOwn(node, part)) {
+            node = node[part];
+        } else {
+            return undefined;
+        }
+    }
+    return node;
+};
+
+for (const fp of bcdJsons) {
+    const src = fs.readFileSync(fp, { encoding: 'utf-8' });
+    const data = JSON.parse(src);
+    let updated = false;
+    for (const [key, feature] of bcdToFeature.entries()) {
+        const node = lookup(data, key);
+        if (!node || !node.__compat) {
+            continue;
+        }
+        bcdToFeature.delete(key);
+
+        const tag = `web-features:${feature}`;
+        const compat = node.__compat;
+        if (compat.tags?.includes(tag)) {
+            continue;
+        }
+        if (compat.tags) {
+            compat.tags.push(tag);
+        } else {
+            compat.tags = [tag];
+        }
+        updated = true;
+    }
+    if (updated) {
+        const src = JSON.stringify(data, null, '  ') + '\n';
+        fs.writeFileSync(fp, src, { encoding: 'utf-8' })
+    }
+}
+
+for (const [key, feature] of bcdToFeature) {
+    console.warn('Not migrated:', feature, key);
+}