Reuse arrays in visitor keys (#18386)

scripts/build/config.js

@@ -598,7 +598,10 @@ const pluginFiles = [
             "const LOCAL_DEBUG = false &&",
           );
 
-          text = text.replace(/(?<=\n)export .*?;/u, "export { preprocess };");
+          text = text.replace(
+            /(?<=\n)export .*?;/u,
+            "export { preprocess, getVoidTags, visitorKeys };",
+          );
 
           return text;
         },

scripts/build/esbuild-plugins/evaluate.js

@@ -1,33 +1,89 @@
+import assert from "node:assert";
+import path from "node:path";
 import url from "node:url";
 import { isValidIdentifier } from "@babel/types";
+import { outdent } from "outdent";
 import serialize from "serialize-javascript";
 
+function serializeModule(module) {
+  return Object.entries(module)
+    .map(([specifier, value]) => {
+      const code =
+        value instanceof RegExp
+          ? `/${value.source}/${value.flags}`
+          : serialize(value, { space: 2, unsafe: true });
+      if (specifier === "default") {
+        return `export default ${code};`;
+      }
+
+      if (!isValidIdentifier(specifier)) {
+        throw new Error(`${specifier} is not a valid specifier`);
+      }
+
+      return `export const ${specifier} = ${code};`;
+    })
+    .join("\n");
+}
+
+function serializeVisitorKeys(module) {
+  const specifiers = Object.keys(module);
+  assert.deepEqual(specifiers, ["default"]);
+
+  const references = new Map();
+  const properties = Object.entries(module.default);
+  for (const [, keys] of properties) {
+    if (!references.has(keys)) {
+      references.set(keys, 1);
+    } else {
+      references.set(keys, references.get(keys) + 1);
+    }
+  }
+
+  const variables = [];
+  const propertiesText = [];
+  for (const [type, keys] of properties) {
+    const isSingleReference = references.get(keys) === 1;
+    const key = isValidIdentifier(type) ? type : JSON.stringify(type);
+    if (isSingleReference) {
+      propertiesText.push(`  ${key}: ${JSON.stringify(keys)},`);
+    } else {
+      if (!variables.includes(keys)) {
+        variables.push(keys);
+      }
+      const index = variables.indexOf(keys);
+      propertiesText.push(`  ${key}: vk[${index}],`);
+    }
+  }
+
+  const code = outdent`
+    const vk = [
+    ${variables.map((keys) => `  ${JSON.stringify(keys)},`).join("\n")}
+    ];
+
+    export default {
+    ${propertiesText.join("\n")}
+    };
+  `;
+
+  return code;
+}
+
 export default function esbuildPluginEvaluate() {
   return {
     name: "evaluate",
     setup(build) {
       build.onLoad(
         { filter: /\.evaluate\.[cm]?js$/, namespace: "file" },
-        async ({ path }) => {
-          const module = await import(url.pathToFileURL(path));
-          const text = Object.entries(module)
-            .map(([specifier, value]) => {
-              const code =
-                value instanceof RegExp
-                  ? `/${value.source}/${value.flags}`
-                  : serialize(value, { space: 2 });
+        async ({ path: filePath }) => {
+          const module = await import(url.pathToFileURL(filePath));
+          const isVisitorKeys =
+            path.basename(filePath, path.extname(filePath)) ===
+            "visitor-keys.evaluate";
 
-              if (specifier === "default") {
-                return `export default ${code};`;
-              }
+          const text = isVisitorKeys
+            ? serializeVisitorKeys(module)
+            : serializeModule(module);
 
-              if (!isValidIdentifier(specifier)) {
-                throw new Error(`${specifier} is not a valid specifier`);
-              }
-
-              return `export const ${specifier} = ${code};`;
-            })
-            .join("\n");
           return { contents: text };
         },
       );