[clangd] Deduplicate symbols collected in global-symbol-builder tool.

[ioeric]

Summary

After D42111, the executor framework no longer deduplicate tool results.

[sammccall]

clangd/global-symbol-builder/GlobalSymbolBuilderMain.cpp

109

nit: this comment could be tightened up a bit:

// FIXME(ioeric): Merge occurrences, rather than just dropping all but one.
// Definitions and forward declarations have the same key and may both have information.
// Usage count will need to be aggregated across occurrences, too.

113

nit: UniqueSymbols? "Reduce" makes sense from an MR perspective but there's not enough context.

116

picking the longest string might be better than random, but I'm not sure if it's enough to be worthwhile.

[ioeric]

Addressed review comments.

[ioeric]

clangd/global-symbol-builder/GlobalSymbolBuilderMain.cpp

109

Thanks!

clangd/global-symbol-builder/GlobalSymbolBuilderMain.cpp

int main(int argc, const char **argv) {
 
   auto Err = Executor->get()->execute(
       llvm::make_unique<clang::clangd::SymbolIndexActionFactory>(
           Executor->get()->getExecutionContext()));
   if (Err) {
     llvm::errs() << llvm::toString(std::move(Err)) << "\n";
   }
 
+  // Deduplicate the result by key.
+  // FIXME(ioeric): we need a better way to merge symbols with the same key. For
+  // example, class forward-declarations can have the same key as the class
+  // definition, and we should merge them instead of ignoring one of them. We
+  // would also need to aggregate signals like usage count when they are added.
+  llvm::StringMap<llvm::StringRef> ReducedSymbols;
   Executor->get()->getToolResults()->forEachResult(
-      [](llvm::StringRef, llvm::StringRef Value) { llvm::outs() << Value; });
+      [&ReducedSymbols](llvm::StringRef Key, llvm::StringRef Value) {
+        ReducedSymbols[Key] = Value;
+      });
+  for (const auto &Sym : ReducedSymbols)
+    llvm::outs() << Sym.second;
   return 0;
 }