tools: simplify tools/doc/preprocess.js

PR-URL: #19539
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>

tools/doc/preprocess.js

@@ -1,58 +1,38 @@
 'use strict';
 
-module.exports = preprocess;
+module.exports = processIncludes;
 
 const path = require('path');
 const fs = require('fs');
 
-const includeExpr = /^@include\s+[\w-]+\.?[a-zA-Z]*$/gmi;
-const includeData = {};
-
-function preprocess(inputFile, input, cb) {
-  input = stripComments(input);
-  processIncludes(inputFile, input, cb);
-}
-
-function stripComments(input) {
-  return input.replace(/^@\/\/.*$/gmi, '');
-}
+const includeExpr = /^@include\s+([\w-]+)(?:\.md)?$/gmi;
+const commentExpr = /^@\/\/.*$/gmi;
 
 function processIncludes(inputFile, input, cb) {
   const includes = input.match(includeExpr);
-  if (includes === null) return cb(null, input);
+  if (includes === null)
+    return cb(null, input.replace(commentExpr, ''));
+
   let errState = null;
   let incCount = includes.length;
 
   includes.forEach((include) => {
-    let fname = include.replace(/^@include\s+/, '');
-    if (!/\.md$/.test(fname)) fname = `${fname}.md`;
-
-    if (includeData.hasOwnProperty(fname)) {
-      input = input.split(include).join(includeData[fname]);
-      incCount--;
-      if (incCount === 0) {
-        return cb(null, input);
-      }
-    }
-
+    const fname = include.replace(includeExpr, '$1.md');
     const fullFname = path.resolve(path.dirname(inputFile), fname);
+
     fs.readFile(fullFname, 'utf8', function(er, inc) {
       if (errState) return;
       if (er) return cb(errState = er);
-      preprocess(inputFile, inc, function(er, inc) {
-        if (errState) return;
-        if (er) return cb(errState = er);
-        incCount--;
-
-        // Add comments to let the HTML generator know how the anchors for
-        // headings should look like.
-        includeData[fname] = `<!-- [start-include:${fname}] -->\n` +
-                             `${inc}\n<!-- [end-include:${fname}] -->\n`;
-        input = input.split(`${include}\n`).join(`${includeData[fname]}\n`);
-        if (incCount === 0) {
-          return cb(null, input);
-        }
-      });
+      incCount--;
+
+      // Add comments to let the HTML generator know
+      // how the anchors for headings should look like.
+      inc = `<!-- [start-include:${fname}] -->\n` +
+            `${inc}\n<!-- [end-include:${fname}] -->\n`;
+      input = input.split(`${include}\n`).join(`${inc}\n`);
+
+      if (incCount === 0)
+        return cb(null, input.replace(commentExpr, ''));
     });
   });
 }