[lldb] Prevent dwim-print from showing kNoResult error

[kastiglione]

Summary

Expression evaluation for void valued expressions sets an error using the kNoResult
code. Like the expression command, dwim-print should also not print such errors.

Before:

(lldb) dwim-print (void)printf("hi\n")
hi
Error: 'unknown error'

After:

(lldb) dwim-print (void)printf("hi\n")
hi

rdar://109746544

[aprantl]

lldb/source/Commands/CommandObjectDWIMPrint.cpp

1

nit: C++ marker is only needed in a .h file ;-)

lldb/source/Commands/CommandObjectDWIMPrint.cpp

 //===-- CommandObjectDWIMPrint.cpp ------------------------------*- C++ -*-===//
 //
 // 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 "CommandObjectDWIMPrint.h"
 
 #include "lldb/Core/ValueObject.h"
 #include "lldb/DataFormatters/DumpValueObjectOptions.h"
 #include "lldb/Expression/ExpressionVariable.h"
+#include "lldb/Expression/UserExpression.h"
 #include "lldb/Interpreter/CommandInterpreter.h"
 #include "lldb/Interpreter/CommandObject.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Interpreter/OptionGroupFormat.h"
 #include "lldb/Interpreter/OptionGroupValueObjectDisplay.h"
 #include "lldb/Target/StackFrame.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/lldb-defines.h"
if (expr_result == eExpressionCompleted) {
       if (verbosity != eDWIMPrintVerbosityNone) {
         StringRef flags;
         if (args.HasArgs())
           flags = args.GetArgStringWithDelimiter();
         result.AppendMessageWithFormatv("note: ran `expression {0}{1}`", flags,
                                         expr);
       }
 
+      if (valobj_sp->GetError().GetError() != UserExpression::kNoResult)
         valobj_sp->Dump(result.GetOutputStream(), dump_options);
 
       if (suppress_result)
         if (auto result_var_sp =
                 target.GetPersistentVariable(valobj_sp->GetName())) {
           auto language = valobj_sp->GetPreferredDisplayLanguage();
           if (auto *persistent_state =
                   target.GetPersistentExpressionStateForLanguage(language))
             persistent_state->RemovePersistentVariable(result_var_sp);

lldb/test/API/commands/dwim-print/TestDWIMPrint.py

def test_summary_strings(self):
         self.build()
         lldbutil.run_to_source_breakpoint(
             self, "// break here", lldb.SBFileSpec("main.c")
         )
         self.runCmd("settings set auto-one-line-summaries false")
         self.runCmd("type summary add -e -s 'stub summary' Structure")
         self._expect_cmd(f"dwim-print s", "frame variable")
         self._expect_cmd(f"dwim-print (struct Structure)s", "expression")
+
+    def test_void_result(self):
+        """Test dwim-print does not surface an error message for void expressions."""
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.c"))
+        self.expect("dwim-print (void)15", matching=False, patterns=["(?i)error"])