[clang-tools-extra] [clang-doc] Add HTMLMustacheGenerator methods (PR #138061)

[Paul Kirth via cfe-commits]

================
@@ -70,18 +70,116 @@ class MustacheTemplateFile : public Template {
   MustacheTemplateFile(StringRef TemplateStr) : Template(TemplateStr) {}
 };
 
+static std::unique_ptr<MustacheTemplateFile> NamespaceTemplate = nullptr;
+
+static std::unique_ptr<MustacheTemplateFile> RecordTemplate = nullptr;
+
+static Error setupTemplateFiles(const clang::doc::ClangDocContext &CDCtx) {
+  return Error::success();
+}
+
 Error MustacheHTMLGenerator::generateDocs(
     StringRef RootDir, StringMap<std::unique_ptr<doc::Info>> Infos,
     const clang::doc::ClangDocContext &CDCtx) {
+  if (auto Err = setupTemplateFiles(CDCtx))
+    return Err;
+  // Track which directories we already tried to create.
+  StringSet<> CreatedDirs;
+  // Collect all output by file name and create the necessary directories.
+  StringMap<std::vector<doc::Info *>> FileToInfos;
+  for (const auto &Group : Infos) {
+    doc::Info *Info = Group.getValue().get();
+
+    SmallString<128> Path;
+    sys::path::native(RootDir, Path);
+    sys::path::append(Path, Info->getRelativeFilePath(""));
+    if (!CreatedDirs.contains(Path)) {
+      if (std::error_code EC = sys::fs::create_directories(Path))
+        return createStringError(EC, "failed to create directory '%s'.",
+                                 Path.c_str());
----------------
ilovepi wrote:

ah, no dice. We hit a static assert in Format.h

```
error: static assertion failed due to requirement 'std::is_scalar_v<llvm::StringRef>': format can't be used with non fundamental / non pointer type
   85 |   static_assert(std::is_scalar_v<Arg>
```

https://github.com/llvm/llvm-project/pull/138061