tools: doc: improve async workflow of generate.js

Use fs.promises for read and write file
Use unified().process wich is async instead processSync
html and json are write in parallel
errors are logged and exit process with `1` code

Fixes: https://github.com/nodejs/node/issues/30090

PR-URL: https://github.com/nodejs/node/pull/30106
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

2 files changed, 58 insertions, 33 deletions

diff --git a/tools/doc/generate.js b/tools/doc/generate.js
index 7be5f3f73f..cd85d53657 100644
--- a/tools/doc/generate.js
+++ b/tools/doc/generate.js
@@ -21,7 +21,7 @@
 
 'use strict';
 
-const fs = require('fs');
+const { promises: fs } = require('fs');
 const path = require('path');
 const unified = require('unified');
 const markdown = require('remark-parse');
@@ -41,36 +41,35 @@ let nodeVersion = null;
 let outputDir = null;
 let apilinks = {};
 
-args.forEach((arg) => {
-  if (!arg.startsWith('--')) {
-    filename = arg;
-  } else if (arg.startsWith('--node-version=')) {
-    nodeVersion = arg.replace(/^--node-version=/, '');
-  } else if (arg.startsWith('--output-directory=')) {
-    outputDir = arg.replace(/^--output-directory=/, '');
-  } else if (arg.startsWith('--apilinks=')) {
-    const linkFile = arg.replace(/^--apilinks=/, '');
-    const data = fs.readFileSync(linkFile, 'utf8');
-    if (!data.trim()) {
-      throw new Error(`${linkFile} is empty`);
+async function main() {
+  for (const arg of args) {
+    if (!arg.startsWith('--')) {
+      filename = arg;
+    } else if (arg.startsWith('--node-version=')) {
+      nodeVersion = arg.replace(/^--node-version=/, '');
+    } else if (arg.startsWith('--output-directory=')) {
+      outputDir = arg.replace(/^--output-directory=/, '');
+    } else if (arg.startsWith('--apilinks=')) {
+      const linkFile = arg.replace(/^--apilinks=/, '');
+      const data = await fs.readFile(linkFile, 'utf8');
+      if (!data.trim()) {
+        throw new Error(`${linkFile} is empty`);
+      }
+      apilinks = JSON.parse(data);
     }
-    apilinks = JSON.parse(data);
   }
-});
 
-nodeVersion = nodeVersion || process.version;
-
-if (!filename) {
-  throw new Error('No input file specified');
-} else if (!outputDir) {
-  throw new Error('No output directory specified');
-}
+  nodeVersion = nodeVersion || process.version;
 
+  if (!filename) {
+    throw new Error('No input file specified');
+  } else if (!outputDir) {
+    throw new Error('No output directory specified');
+  }
 
-fs.readFile(filename, 'utf8', async (er, input) => {
-  if (er) throw er;
+  const input = await fs.readFile(filename, 'utf8');
 
-  const content = unified()
+  const content = await unified()
     .use(markdown)
     .use(html.preprocessText)
     .use(json.jsonAPI, { filename })
@@ -80,14 +79,40 @@ fs.readFile(filename, 'utf8', async (er, input) => {
     .use(remark2rehype, { allowDangerousHTML: true })
     .use(raw)
     .use(htmlStringify)
-    .processSync(input);
-
-  const basename = path.basename(filename, '.md');
+    .process(input);
 
   const myHtml = await html.toHTML({ input, content, filename, nodeVersion });
+  const basename = path.basename(filename, '.md');
   const htmlTarget = path.join(outputDir, `${basename}.html`);
-  fs.writeFileSync(htmlTarget, myHtml);
-
   const jsonTarget = path.join(outputDir, `${basename}.json`);
-  fs.writeFileSync(jsonTarget, JSON.stringify(content.json, null, 2));
-});
+
+  return Promise.allSettled([
+    fs.writeFile(htmlTarget, myHtml),
+    fs.writeFile(jsonTarget, JSON.stringify(content.json, null, 2)),
+  ]);
+}
+
+main()
+  .then((tasks) => {
+    // Filter rejected tasks
+    const errors = tasks.filter(({ status }) => status === 'rejected')
+      .map(({ reason }) => reason);
+
+    // Log errors
+    for (const error of errors) {
+      console.error(error);
+    }
+
+    // Exit process with code 1 if some errors
+    if (errors.length > 0) {
+      return process.exit(1);
+    }
+
+    // Else with code 0
+    process.exit(0);
+  })
+  .catch((error) => {
+    console.error(error);
+
+    process.exit(1);
+  });
diff --git a/tools/doc/package.json b/tools/doc/package.json
index 1d2953b023..11f6c76c91 100644
--- a/tools/doc/package.json
+++ b/tools/doc/package.json
@@ -4,7 +4,7 @@
   "description": "Internal tool for generating Node.js API docs",
   "version": "0.0.0",
   "engines": {
-    "node": ">=6"
+    "node": ">=12.10.0"
   },
   "dependencies": {
     "rehype-raw": "^2.0.0",