Merge pull request swiftlang#21605 from DavidGoldman/sourcekit_invocation_error

[SourceKit] Use diagnostics for arg parsing

Author: benlangmuir

include/swift/AST/DiagnosticEngine.h

@@ -596,6 +596,12 @@ namespace swift {
       Consumers.push_back(&Consumer);
     }
 
+    /// Remove a specific DiagnosticConsumer.
+    void removeConsumer(DiagnosticConsumer &Consumer) {
+      Consumers.erase(
+          std::remove(Consumers.begin(), Consumers.end(), &Consumer));
+    }
+
     /// Remove and return all \c DiagnosticConsumers.
     std::vector<DiagnosticConsumer *> takeConsumers() {
       auto Result = std::vector<DiagnosticConsumer*>(Consumers.begin(),

tools/SourceKit/lib/SwiftLang/SwiftASTManager.cpp

@@ -438,14 +438,21 @@ bool SwiftASTManager::initCompilerInvocation(CompilerInvocation &Invocation,
   Args.push_back(Impl.RuntimeResourcePath.c_str());
   Args.append(OrigArgs.begin(), OrigArgs.end());
 
+  SmallString<32> ErrStr;
+  llvm::raw_svector_ostream ErrOS(ErrStr);
+  StreamDiagConsumer DiagConsumer(ErrOS);
+  Diags.addConsumer(DiagConsumer);
+
   bool HadError = driver::getSingleFrontendInvocationFromDriverArguments(
       Args, Diags, [&](ArrayRef<const char *> FrontendArgs) {
     return Invocation.parseArgs(FrontendArgs, Diags);
   });
 
+  // Remove the StreamDiagConsumer as it's no longer needed.
+  Diags.removeConsumer(DiagConsumer);
+
   if (HadError) {
-    // FIXME: Get the actual diagnostic.
-    Error = "error when parsing the compiler arguments";
+    Error = ErrOS.str();
     return true;
   }
 
@@ -493,20 +500,9 @@ bool SwiftASTManager::initCompilerInvocation(CompilerInvocation &CompInvok,
                                              ArrayRef<const char *> OrigArgs,
                                              StringRef PrimaryFile,
                                              std::string &Error) {
-
-  SmallString<32> ErrStr;
-  llvm::raw_svector_ostream ErrOS(ErrStr);
   DiagnosticEngine Diagnostics(Impl.SourceMgr);
-  StreamDiagConsumer DiagConsumer(ErrOS);
-  Diagnostics.addConsumer(DiagConsumer);
-
-  if (initCompilerInvocation(CompInvok, OrigArgs, Diagnostics, PrimaryFile,
-                             Error)) {
-    if (!ErrOS.str().empty())
-      Error = ErrOS.str();
-    return true;
-  }
-  return false;
+  return initCompilerInvocation(CompInvok, OrigArgs, Diagnostics, PrimaryFile,
+                                Error);
 }
 
 bool SwiftASTManager::initCompilerInvocationNoInputs(