[flang][Driver] Better error message when multiple actions are specified (#165575)

If multiple action options are specified on the command line, list them all 
in the error message that is emitted

Fixes #79458

Author: tarunprabhu

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -312,6 +312,8 @@ def warn_drv_yc_multiple_inputs_clang_cl : Warning<
 def warn_drv_potentially_misspelled_joined_argument : Warning<
   "joined argument treated as '%0'; did you mean '%1'?">, InGroup<UnknownArgument>;
 
+def err_drv_too_many_actions: Error<
+    "only one action option is allowed. Got %0">;
 def err_drv_invalid_value : Error<"invalid value '%1' in '%0'">;
 def err_drv_invalid_int_value : Error<"invalid integral value '%1' in '%0'">;
 def err_drv_invalid_value_with_suggestion : Error<

flang/lib/Frontend/CompilerInvocation.cpp

@@ -595,9 +595,15 @@ static bool parseFrontendArgs(FrontendOptions &opts, llvm::opt::ArgList &args,
   // -cc1` does accept multiple action options, but will only consider the
   // rightmost one.
   if (args.hasMultipleArgs(clang::driver::options::OPT_Action_Group)) {
-    const unsigned diagID = diags.getCustomDiagID(
-        clang::DiagnosticsEngine::Error, "Only one action option is allowed");
-    diags.Report(diagID);
+    llvm::SmallString<32> buf;
+    llvm::raw_svector_ostream os(buf);
+    for (const llvm::opt::Arg *arg :
+         args.filtered(clang::driver::options::OPT_Action_Group)) {
+      if (buf.size())
+        os << ", ";
+      os << "'" << arg->getSpelling() << "'";
+    }
+    diags.Report(clang::diag::err_drv_too_many_actions) << buf;
     return false;
   }
 

flang/test/Driver/multiple-actions-error.f95

@@ -1,8 +1,30 @@
-! Verify that the frontend driver error-out if multiple actions are specified
-
-! RUN: not %flang_fc1 -E -fsyntax-only %s 2>&1 | FileCheck %s --check-prefix=ERROR
-! RUN: not %flang_fc1 -fsyntax-only -fsyntax-only %s 2>&1 | FileCheck %s --check-prefix=ERROR
-
-! ERROR: error: Only one action option is allowed
-
-end progream
+! Verify that the frontend driver raises the expected error when multiple
+! actions are specified.
+!
+! RUN: not %flang_fc1 -fsyntax-only -fsyntax-only %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-1
+!
+! RUN: not %flang_fc1 -E -fsyntax-only %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-2
+!
+! RUN: not %flang_fc1 -fsyntax-only -E -emit-llvm %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-3
+!
+! If one or more options are specified with -Xflang, they will appear last in
+! the error message.
+!
+! RUN: not %flang -S -Xflang -emit-llvm %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-4
+!
+! RUN: not %flang -Xflang -emit-llvm -S %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-4
+!
+! RUN: not %flang -Xflang -emit-obj -S -Xflang -emit-llvm %s 2>&1 \
+! RUN:     | FileCheck %s --check-prefixes=ERROR,ACTIONS-5
+!
+! ERROR: error: only one action option is allowed.
+! ACTIONS-1: Got '-fsyntax-only', '-fsyntax-only'
+! ACTIONS-2: Got '-E', '-fsyntax-only'
+! ACTIONS-3: Got '-fsyntax-only', '-E', '-emit-llvm'
+! ACTIONS-4: Got '-S', '-emit-llvm'
+! ACTIONS-5: Got '-S', '-emit-obj', '-emit-llvm'