[Swift] Implement error handling for dwim-print -O

lldb/include/lldb/Core/ValueObject.h

@@ -522,7 +522,7 @@ class ValueObject {
                            std::string &destination,
                            const TypeSummaryOptions &options);
 
-  const char *GetObjectDescription();
+  llvm::Expected<std::string> GetObjectDescription();
 
   bool HasSpecialPrintableRepresentation(
       ValueObjectRepresentationStyle val_obj_display,
@@ -657,9 +657,9 @@ class ValueObject {
 
   virtual SymbolContextScope *GetSymbolContextScope();
 
-  void Dump(Stream &s);
+  llvm::Error Dump(Stream &s);
 
-  void Dump(Stream &s, const DumpValueObjectOptions &options);
+  llvm::Error Dump(Stream &s, const DumpValueObjectOptions &options);
 
   static lldb::ValueObjectSP
   CreateValueObjectFromExpression(llvm::StringRef name,

lldb/include/lldb/DataFormatters/ValueObjectPrinter.h

@@ -34,7 +34,7 @@ class ValueObjectPrinter {
 
   ~ValueObjectPrinter() = default;
 
-  bool PrintValueObject();
+  llvm::Error PrintValueObject();
 
 protected:
   typedef std::set<uint64_t> InstancePointersSet;
@@ -76,7 +76,7 @@ class ValueObjectPrinter {
 
   void SetupMostSpecializedValue();
 
-  const char *GetDescriptionForDisplay();
+  llvm::Expected<std::string> GetDescriptionForDisplay();
 
   const char *GetRootNameForDisplay();
 
@@ -109,7 +109,8 @@ class ValueObjectPrinter {
 
   bool PrintValueAndSummaryIfNeeded(bool &value_printed, bool &summary_printed);
 
-  bool PrintObjectDescriptionIfNeeded(bool value_printed, bool summary_printed);
+  llvm::Error PrintObjectDescriptionIfNeeded(bool value_printed,
+                                             bool summary_printed);
 
   bool
   ShouldPrintChildren(DumpValueObjectOptions::PointerDepth &curr_ptr_depth);
@@ -133,7 +134,7 @@ class ValueObjectPrinter {
   PrintChildren(bool value_printed, bool summary_printed,
                 const DumpValueObjectOptions::PointerDepth &curr_ptr_depth);
 
-  void PrintChildrenIfNeeded(bool value_printed, bool summary_printed);
+  llvm::Error PrintChildrenIfNeeded(bool value_printed, bool summary_printed);
 
   bool PrintChildrenOneLiner(bool hide_names);
 

lldb/include/lldb/Target/LanguageRuntime.h

@@ -74,11 +74,12 @@ class LanguageRuntime : public Runtime, public PluginInterface {
     return nullptr;
   }
 
-  virtual bool GetObjectDescription(Stream &str, ValueObject &object) = 0;
-
-  virtual bool GetObjectDescription(Stream &str, Value &value,
-                                    ExecutionContextScope *exe_scope) = 0;
+  virtual llvm::Error GetObjectDescription(Stream &str,
+                                           ValueObject &object) = 0;
 
+  virtual llvm::Error
+  GetObjectDescription(Stream &str, Value &value,
+                       ExecutionContextScope *exe_scope) = 0;
 
   struct VTableInfo {
     Address addr; /// Address of the vtable's virtual function table

lldb/include/lldb/Utility/ErrorMessages.h

@@ -0,0 +1,22 @@
+//===-- ErrorMessages.h -----------------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_UTILITY_ERROR_MESSAGES_H
+#define LLDB_UTILITY_ERROR_MESSAGES_H
+
+#include "lldb/lldb-defines.h"
+#include "lldb/lldb-enumerations.h"
+#include <string>
+
+namespace lldb_private {
+
+/// Produce a human-readable rendition of an ExpressionResults value.
+std::string toString(lldb::ExpressionResults e);
+
+} // namespace lldb_private
+#endif

lldb/source/API/SBValue.cpp

@@ -379,7 +379,10 @@ const char *SBValue::GetObjectDescription() {
   if (!value_sp)
     return nullptr;
 
-  return ConstString(value_sp->GetObjectDescription()).GetCString();
+  llvm::Expected<std::string> str = value_sp->GetObjectDescription();
+  if (!str)
+    return ConstString("error: " + toString(str.takeError())).AsCString();
+  return ConstString(*str).AsCString();
 }
 
 SBType SBValue::GetType() {
@@ -1210,11 +1213,14 @@ bool SBValue::GetDescription(SBStream &description) {
 
   ValueLocker locker;
   lldb::ValueObjectSP value_sp(GetSP(locker));
-  if (value_sp)
-    value_sp->Dump(strm);
-  else
+  if (value_sp) {
+    if (llvm::Error error = value_sp->Dump(strm)) {
+      strm << "error: " << toString(std::move(error));
+      return false;
+    }
+  } else {
     strm.PutCString("No value");
-
+  }
   return true;
 }
 

lldb/source/Breakpoint/Watchpoint.cpp

@@ -301,7 +301,9 @@ bool Watchpoint::DumpSnapshots(Stream *s, const char *prefix) const {
             .SetHideRootType(true)
             .SetHideRootName(true)
             .SetHideName(true);
-        m_old_value_sp->Dump(strm, options);
+        if (llvm::Error error = m_old_value_sp->Dump(strm, options))
+          strm << "error: " << toString(std::move(error));
+
         if (strm.GetData())
           values_ss.Printf("old value: %s", strm.GetData());
       }
@@ -324,7 +326,9 @@ bool Watchpoint::DumpSnapshots(Stream *s, const char *prefix) const {
             .SetHideRootType(true)
             .SetHideRootName(true)
             .SetHideName(true);
-        m_new_value_sp->Dump(strm, options);
+        if (llvm::Error error = m_new_value_sp->Dump(strm, options))
+          strm << "error: " << toString(std::move(error));
+
         if (strm.GetData())
           values_ss.Printf("new value: %s", strm.GetData());
       }

lldb/source/Commands/CommandObjectDWIMPrint.cpp

@@ -138,6 +138,28 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
     }
   };
 
+  // Dump `valobj` according to whether `po` was requested or not.
+  auto dump_val_object = [&](ValueObject &valobj) {
+    if (is_po) {
+      StreamString temp_result_stream;
+      if (llvm::Error error = valobj.Dump(temp_result_stream, dump_options)) {
+        result.AppendError(toString(std::move(error)));
+        return;
+      }
+      llvm::StringRef output = temp_result_stream.GetString();
+      maybe_add_hint(output);
+      result.GetOutputStream() << output;
+    } else {
+      llvm::Error error =
+        valobj.Dump(result.GetOutputStream(), dump_options);
+      if (error) {
+        result.AppendError(toString(std::move(error)));
+        return;
+      }
+    }
+    result.SetStatus(eReturnStatusSuccessFinishResult);
+  };
+
   // First, try `expr` as the name of a frame variable.
   if (frame) {
     auto valobj_sp = frame->FindVariable(ConstString(expr));
@@ -155,16 +177,7 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
                                         flags, expr);
       }
 
-      if (is_po) {
-        StreamString temp_result_stream;
-        valobj_sp->Dump(temp_result_stream, dump_options);
-        llvm::StringRef output = temp_result_stream.GetString();
-        maybe_add_hint(output);
-        result.GetOutputStream() << output;
-      } else {
-        valobj_sp->Dump(result.GetOutputStream(), dump_options);
-      }
-      result.SetStatus(eReturnStatusSuccessFinishResult);
+      dump_val_object(*valobj_sp);
       return;
     }
   }
@@ -211,8 +224,7 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
     if (auto *state = target.GetPersistentExpressionStateForLanguage(language))
       if (auto var_sp = state->GetVariable(expr))
         if (auto valobj_sp = var_sp->GetValueObject()) {
-          valobj_sp->Dump(result.GetOutputStream(), dump_options);
-          result.SetStatus(eReturnStatusSuccessFinishResult);
+          dump_val_object(*valobj_sp);
           return;
         }
 
@@ -233,43 +245,36 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
       error_stream << "    " << fixed_expression << "\n";
     }
 
-    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) {
-        if (is_po) {
-          StreamString temp_result_stream;
-          valobj_sp->Dump(temp_result_stream, dump_options);
-          llvm::StringRef output = temp_result_stream.GetString();
-          maybe_add_hint(output);
-          result.GetOutputStream() << output;
-        } else {
-          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);
-        }
-
-      result.SetStatus(eReturnStatusSuccessFinishResult);
-    } else {
+    // If the expression failed, return an error.
+    if (expr_result != eExpressionCompleted) {
       if (valobj_sp)
         result.SetError(valobj_sp->GetError());
       else
         result.AppendErrorWithFormatv(
             "unknown error evaluating expression `{0}`", expr);
+      return;
+    }
+
+    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)
+      dump_val_object(*valobj_sp);
+    else
+      result.SetStatus(eReturnStatusSuccessFinishResult);
+
+    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/source/Commands/CommandObjectExpression.cpp

@@ -497,7 +497,11 @@ bool CommandObjectExpression::EvaluateExpression(llvm::StringRef expr,
         options.SetVariableFormatDisplayLanguage(
             result_valobj_sp->GetPreferredDisplayLanguage());
 
-        result_valobj_sp->Dump(output_stream, options);
+        if (llvm::Error error =
+                result_valobj_sp->Dump(output_stream, options)) {
+          result.AppendError(toString(std::move(error)));
+          return false;
+        }
 
         if (suppress_result)
           if (auto result_var_sp =

lldb/source/Commands/CommandObjectFrame.cpp

@@ -182,7 +182,8 @@ class CommandObjectFrameDiagnose : public CommandObjectParsed {
     assert(valobj_sp.get() && "Must have a valid ValueObject to print");
     ValueObjectPrinter printer(*valobj_sp, &result.GetOutputStream(),
                                options);
-    printer.PrintValueObject();
+    if (llvm::Error error = printer.PrintValueObject())
+      result.AppendError(toString(std::move(error)));
   }
 
   CommandOptions m_options;
@@ -609,7 +610,9 @@ may even involve JITing and running code in the target program.)");
                                                 show_module))
                       s.PutCString(": ");
                   }
-                  valobj_sp->Dump(result.GetOutputStream(), options);
+                  auto &strm = result.GetOutputStream();
+                  if (llvm::Error error = valobj_sp->Dump(strm, options))
+                    result.AppendError(toString(std::move(error)));
                 }
               }
             } else {
@@ -651,7 +654,8 @@ may even involve JITing and running code in the target program.)");
               Stream &output_stream = result.GetOutputStream();
               options.SetRootValueObjectName(
                   valobj_sp->GetParent() ? entry.c_str() : nullptr);
-              valobj_sp->Dump(output_stream, options);
+              if (llvm::Error error = valobj_sp->Dump(output_stream, options))
+                result.AppendError(toString(std::move(error)));
             } else {
               if (auto error_cstr = error.AsCString(nullptr))
                 result.AppendError(error_cstr);
@@ -702,7 +706,9 @@ may even involve JITing and running code in the target program.)");
                     valobj_sp->GetPreferredDisplayLanguage());
                 options.SetRootValueObjectName(
                     var_sp ? var_sp->GetName().AsCString() : nullptr);
-                valobj_sp->Dump(result.GetOutputStream(), options);
+                if (llvm::Error error =
+                        valobj_sp->Dump(result.GetOutputStream(), options))
+                  result.AppendError(toString(std::move(error)));
               }
             }
           }
@@ -723,7 +729,9 @@ may even involve JITing and running code in the target program.)");
             options.SetVariableFormatDisplayLanguage(
                 rec_value_sp->GetPreferredDisplayLanguage());
             options.SetRootValueObjectName(rec_value_sp->GetName().AsCString());
-            rec_value_sp->Dump(result.GetOutputStream(), options);
+            if (llvm::Error error =
+                    rec_value_sp->Dump(result.GetOutputStream(), options))
+              result.AppendError(toString(std::move(error)));
           }
         }
       }

lldb/source/Commands/CommandObjectMemory.cpp

@@ -815,7 +815,10 @@ class CommandObjectMemoryRead : public CommandObjectParsed {
           DumpValueObjectOptions options(m_varobj_options.GetAsDumpOptions(
               eLanguageRuntimeDescriptionDisplayVerbosityFull, format));
 
-          valobj_sp->Dump(*output_stream_p, options);
+          if (llvm::Error error = valobj_sp->Dump(*output_stream_p, options)) {
+            result.AppendError(toString(std::move(error)));
+            return;
+          }
         } else {
           result.AppendErrorWithFormat(
               "failed to create a value object for: (%s) %s\n",

lldb/source/Commands/CommandObjectTarget.cpp

@@ -812,7 +812,8 @@ class CommandObjectTargetVariable : public CommandObjectParsed {
 
     options.SetRootValueObjectName(root_name);
 
-    valobj_sp->Dump(s, options);
+    if (llvm::Error error = valobj_sp->Dump(s, options))
+      s << "error: " << toString(std::move(error));
   }
 
   static size_t GetVariableCallback(void *baton, const char *name,

lldb/source/Commands/CommandObjectThread.cpp

@@ -1367,7 +1367,10 @@ class CommandObjectThreadException : public CommandObjectIterateOverThreads {
     Stream &strm = result.GetOutputStream();
     ValueObjectSP exception_object_sp = thread_sp->GetCurrentException();
     if (exception_object_sp) {
-      exception_object_sp->Dump(strm);
+      if (llvm::Error error = exception_object_sp->Dump(strm)) {
+        result.AppendError(toString(std::move(error)));
+        return false;
+      }
     }
 
     ThreadSP exception_thread_sp = thread_sp->GetCurrentExceptionBacktrace();
@@ -1419,9 +1422,12 @@ class CommandObjectThreadSiginfo : public CommandObjectIterateOverThreads {
       return false;
     }
     ValueObjectSP exception_object_sp = thread_sp->GetSiginfoValue();
-    if (exception_object_sp)
-      exception_object_sp->Dump(strm);
-    else
+    if (exception_object_sp) {
+      if (llvm::Error error = exception_object_sp->Dump(strm)) {
+        result.AppendError(toString(std::move(error)));
+        return false;
+      }
+    } else
       strm.Printf("(no siginfo)\n");
     strm.PutChar('\n');