[clang] [clang][modules] Separate parsing of modulemaps (PR #119740)

[Michael Spencer via cfe-commits]

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@@ -3157,25 +2140,18 @@ bool ModuleMap::parseModuleMapFile(FileEntryRef File, bool IsSystem,
   assert((!Offset || *Offset <= Buffer->getBufferSize()) &&
          "invalid buffer offset");
 
-  // Parse this module map file.
-  Lexer L(SourceMgr.getLocForStartOfFile(ID), MMapLangOpts,
-          Buffer->getBufferStart(),
-          Buffer->getBufferStart() + (Offset ? *Offset : 0),
-          Buffer->getBufferEnd());
-  SourceLocation Start = L.getSourceLocation();
-  ModuleMapParser Parser(L, SourceMgr, Target, Diags, *this, ID, Dir, IsSystem);
-  bool Result = Parser.parseModuleMapFile();
-  ParsedModuleMap[File] = Result;
-
-  if (Offset) {
-    auto Loc = SourceMgr.getDecomposedLoc(Parser.getLocation());
-    assert(Loc.first == ID && "stopped in a different file?");
-    *Offset = Loc.second;
+  std::optional<modulemap::ModuleMapFile> MMF = modulemap::parseModuleMap(
+      ID, Dir, SourceMgr, Diags, IsSystem, Offset);
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Bigcheese wrote:

I plan to add a separate source manager and then remap the source locations when constructing the `clang::Module` instance. I plan to do it after looking up modules by header is also lazy.

https://github.com/llvm/llvm-project/pull/119740