[flang][driver] Report prescanning diags during syntax-only parsing

[FarisRehman]

Summary

Ensure diagnostics from the prescanner are reported when running flang-new -fsyntax-only (i.e. only syntax parsing).
This keeps the diagnostics output of flang-new consistent with f18 -fparse-only when running the syntax parsing action, ParseSyntaxOnlyAction.

Summary of changes:

• Modify ParseSyntaxOnlyAction::ExecuteAction to report diagnostics

[awarzynski]

flang/test/Frontend/prescanner-diag.f90

3

In this test we want to make sure that f18 and flang-new behave similarly in the context of generating diagnostics. As per our spreadsheet:

• flang-new -fsyntax-only and
• f18 -fparse-only

should behave similarly. Could you add RUN line with f18 -parse-only?

[FarisRehman]

Add f18 RUN line

Address review comment by @awarzynski

Summary of changes:

• Add a RUN line for f18 -fparse-only to the regression test

[awarzynski]

Thank you for working on this @FarisRehman ! LGTM

flang/test/Frontend/prescanner-diag.f90

3

[nit] Currently there's only one "preprocessor" action, but there are likely to be more in the future. So this might become ambiguous.

I suggest either PrintPreprocessedAction or Test with -E (i.e. PrintPreprocessedAction, stops after prescanning) and Test with -fsyntax-only (i.e. ParseSyntaxOnlyAction, stops after semantic checks)

flang/lib/Frontend/FrontendActions.cpp

 //===--- FrontendActions.cpp ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "flang/Frontend/FrontendActions.h"
 #include "flang/Common/default-kinds.h"
 #include "flang/Frontend/CompilerInstance.h"
 #include "flang/Parser/parsing.h"
 #include "flang/Parser/provenance.h"
 #include "flang/Parser/source.h"
 #include "flang/Semantics/semantics.h"
 
 using namespace Fortran::frontend;
unsigned diagID = ci.diagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, "Could not parse %0");
     ci.diagnostics().Report(diagID) << GetCurrentFileOrBufferName();
 
     ci.parsing().messages().Emit(
         llvm::errs(), this->instance().allCookedSources());
     return;
   }
 
+  // Report the diagnostics from parsing
+  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+
   auto &parseTree{*ci.parsing().parseTree()};
 
   // Prepare semantics
   Fortran::semantics::SemanticsContext semanticsContext{
       defaultKinds, features, ci.allCookedSources()};
   Fortran::semantics::Semantics semantics{
       semanticsContext, parseTree, ci.parsing().cooked().AsCharBlock()};
 

flang/test/Frontend/prescanner-diag.f90

 ! RUN: %f18 -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
 ! RUN: %flang-new -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
+! RUN: %flang-new -fsyntax-only -I %S/Inputs/ %s 2>&1 | FileCheck %s
 ! RUN: %flang-new -fc1 -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
+! RUN: %flang-new -fc1 -fsyntax-only -I %S/Inputs/ %s 2>&1 | FileCheck %s
 
 ! Test that the driver correctly reports diagnostics from the prescanner. The contents of the include file are irrelevant here.
 
-! CHECK: preprocessor-diag.f90:8:20: #include: extra stuff ignored after file name
+! CHECK: prescanner-diag.f90:10:20: #include: extra stuff ignored after file name
 #include <empty.h> comment
-! CHECK: preprocessor-diag.f90:10:20: #include: extra stuff ignored after file name
+! CHECK: prescanner-diag.f90:12:20: #include: extra stuff ignored after file name
 #include "empty.h" comment
 end