Reenable external categories (#87357)

Reenables b31414bf4f9898f7817a9fcf8a91f62ec26f3eaf.

Also adds a new warning for missing `--symbol-graph-dir` arg when
`--emit-extension-symbol-graphs` is provided. This also reverts the
commit that removed.

1 files changed, 7 insertions, 3 deletions

diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 2446aee..f85f036 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -181,9 +181,13 @@ CreateFrontendAction(CompilerInstance &CI) {
 #endif
 
   // Wrap the base FE action in an extract api action to generate
-  // symbol graph as a biproduct of compilation ( enabled with
-  // --emit-symbol-graph option )
-  if (!FEOpts.SymbolGraphOutputDir.empty()) {
+  // symbol graph as a biproduct of compilation (enabled with
+  // --emit-symbol-graph option)
+  if (FEOpts.EmitSymbolGraph) {
+    if (FEOpts.SymbolGraphOutputDir.empty()) {
+      CI.getDiagnostics().Report(diag::warn_missing_symbol_graph_dir);
+      CI.getFrontendOpts().SymbolGraphOutputDir = ".";
+    }
     CI.getCodeGenOpts().ClearASTBeforeBackend = false;
     Act = std::make_unique<WrappingExtractAPIAction>(std::move(Act));
   }