[clang-doc] add async loading (#93276)

PeterChou1 · web-flow · commit a9b1e80acbb3 · 2024-06-30T08:52:36.000-07:00
Fixes #93273 This patch changes the way clang-doc loads html indexes. Previously clang-doc loaded the index via an index_json.js file which uses JSON.parse to parse the file. This patches changes that to use an async function called LoadIndex which enables asynchronous loading making the initial page load not be blocked by loading a large JavaScript object.
diff --git a/clang-tools-extra/clang-doc/HTMLGenerator.cpp b/clang-tools-extra/clang-doc/HTMLGenerator.cpp
@@ -993,9 +993,9 @@ static llvm::Error serializeIndex(ClangDocContext &CDCtx) {
       });
     });
   };
-  OS << "var JsonIndex = `\n";
+  OS << "async function LoadIndex() {\nreturn";
   IndexToJSON(CDCtx.Idx);
-  OS << "`;\n";
+  OS << ";\n}";
   return llvm::Error::success();
 }
 
diff --git a/clang-tools-extra/clang-doc/assets/index.js b/clang-tools-extra/clang-doc/assets/index.js
@@ -80,8 +80,8 @@ function createIndex(Index) {
 
 // Runs after DOM loads
 document.addEventListener("DOMContentLoaded", function() {
-  // JsonIndex is a variable from another file that contains the index
-  // in JSON format
-  var Index = JSON.parse(JsonIndex);
-  createIndex(Index);
+  // LoadIndex is an asynchronous function that will be generated clang-doc.
+  // It ensures that the function call will not block as soon the page loads,
+  // since the index object are often huge and can contain thousands of lines.
+  LoadIndex().then((Index) => { createIndex(Index); });
 });
diff --git a/clang-tools-extra/test/clang-doc/basic-project.test b/clang-tools-extra/test/clang-doc/basic-project.test
@@ -7,8 +7,8 @@
 // RUN: FileCheck %s -input-file=%t/docs/GlobalNamespace/Rectangle.html -check-prefix=HTML-RECTANGLE
 // RUN: FileCheck %s -input-file=%t/docs/GlobalNamespace/Circle.html -check-prefix=HTML-CIRCLE
 
-// JSON-INDEX: var JsonIndex = `
-// JSON-INDEX-NEXT: {
+// JSON-INDEX: async function LoadIndex() {
+// JSON-INDEX-NEXT: return{
 // JSON-INDEX-NEXT:   "USR": "{{([0-9A-F]{40})}}",
 // JSON-INDEX-NEXT:   "Name": "",
 // JSON-INDEX-NEXT:   "RefType": "default",
@@ -51,7 +51,8 @@
 // JSON-INDEX-NEXT:       ]
 // JSON-INDEX-NEXT:     }
 // JSON-INDEX-NEXT:   ]
-// JSON-INDEX-NEXT: }`;
+// JSON-INDEX-NEXT: };
+// JSON-INDEX-NEXT: }
 
 // HTML-SHAPE: <!DOCTYPE html>
 // HTML-SHAPE-NEXT: <meta charset="utf-8"/>
