[LLDB] Fix IOHandlerEditline::GetCurrentLines()

[wallace]

Summary

This method was working as expected if LLDB_ENABLE_LIBEDIT is false, however, if it was true, then the variable m_current_lines_ptr was always pointing to an empty list, because Editline only updates its contents once the full input has been completed (see https://github.com/llvm/llvm-project/blob/main/lldb/source/Host/common/Editline.cpp#L1576).

A simple fix is to invoke Editline::GetInputAsStringList() from GetCurrentLines(), which is already used in many places as the common way to get the full input list.

[aprantl]

Is this covered by any tests?

lldb/source/Core/IOHandler.cpp

512

I think this would benefit from a comment explaining the difference?

lldb/source/Expression/REPL.cpp

535

for (const char *line_cstr : current_lines) ?

[wallace]

lldb/source/Expression/REPL.cpp

535

actually the current code is fine because we don't want to iterate through the entire set, we just want the first current_line_idx + 1 elements

[wallace]

@aprantl , it turns out that there are no tests for this. I also don't know how easy it'd be to test this very specific feature, because it relies on the terminal not being affected by stuff like test runners.

lldb/include/lldb/Core/IOHandler.h

public:
   bool GetLines(StringList &lines, bool &interrupted);
 
   void SetBaseLineNumber(uint32_t line);
 
   bool GetInterruptExits() { return m_interrupt_exits; }
 
   void SetInterruptExits(bool b) { m_interrupt_exits = b; }
 
-  const StringList *GetCurrentLines() const { return m_current_lines_ptr; }
+  StringList GetCurrentLines() const;
 
   uint32_t GetCurrentLineIndex() const;
 
   void PrintAsync(const char *s, size_t len, bool is_stdout) override;
 
 private:
 #if LLDB_ENABLE_LIBEDIT
   bool IsInputCompleteCallback(Editline *editline, StringList &lines);

lldb/include/lldb/Host/Editline.h

public:
   /// Prompts for and reads a single line of user input.
   bool GetLine(std::string &line, bool &interrupted);
 
   /// Prompts for and reads a multi-line batch of user input.
   bool GetLines(int first_line_number, StringList &lines, bool &interrupted);
 
   void PrintAsync(Stream *stream, const char *s, size_t len);
 
+  /// Convert the current input lines into a UTF8 StringList
+  StringList GetInputAsStringList(int line_count = UINT32_MAX);
+
 private:
   /// Sets the lowest line number for multi-line editing sessions.  A value of
   /// zero suppresses
   /// line number printing in the prompt.
   void SetBaseLineNumber(int line_number);
 
   /// Returns the complete prompt by combining the prompt or continuation prompt
   /// with line numbers
private:
   /// taking into account both
   /// the preceding prompt and a single trailing space occupied by a cursor when
   /// at the end of the line.
   int CountRowsForLine(const EditLineStringType &content);
 
   /// Save the line currently being edited
   void SaveEditedLine();
 
-  /// Convert the current input lines into a UTF8 StringList
-  StringList GetInputAsStringList(int line_count = UINT32_MAX);
-
   /// Replaces the current multi-line session with the next entry from history.
   unsigned char RecallHistory(HistoryOperation op);
 
   /// Character reading implementation for EditLine that supports our multi-line
   /// editing trickery.
   int GetCharacter(EditLineGetCharType *c);
 
   /// Prompt implementation for EditLine.

lldb/source/Core/IOHandler.cpp

 uint32_t IOHandlerEditline::GetCurrentLineIndex() const {
 #if LLDB_ENABLE_LIBEDIT
   if (m_editline_up)
     return m_editline_up->GetCurrentLine();
 #endif
   return m_curr_line_idx;
 }
 
+StringList IOHandlerEditline::GetCurrentLines() const {
+#if LLDB_ENABLE_LIBEDIT
+  if (m_editline_up)
+    return m_editline_up->GetInputAsStringList();
+#endif
+  // When libedit is not used, the current lines can be gotten from
+  // `m_current_lines_ptr`, which is updated whenever a new line is processed.
+  // This doesn't happen when libedit is used, in which case
+  // `m_current_lines_ptr` is only updated when the full input is terminated.
+
+  if (m_current_lines_ptr)
+    return *m_current_lines_ptr;
+  return StringList();
+}
+
 bool IOHandlerEditline::GetLines(StringList &lines, bool &interrupted) {
   m_current_lines_ptr = &lines;
 
   bool success = false;
 #if LLDB_ENABLE_LIBEDIT
   if (m_editline_up) {
     return m_editline_up->GetLines(m_base_line_number, lines, interrupted);
   } else {

lldb/source/Expression/REPL.cpp

if (request.GetRawLine().trim().empty()) {
     request.AddCompletion(m_indent_str);
     return;
   }
 
   std::string current_code;
   current_code.append(m_code.CopyList());
 
   IOHandlerEditline &editline = static_cast<IOHandlerEditline &>(io_handler);
-  const StringList *current_lines = editline.GetCurrentLines();
-  if (current_lines) {
-    const uint32_t current_line_idx = editline.GetCurrentLineIndex();
+  StringList current_lines = editline.GetCurrentLines();
 
-    if (current_line_idx < current_lines->GetSize()) {
-      for (uint32_t i = 0; i < current_line_idx; ++i) {
-        const char *line_cstr = current_lines->GetStringAtIndex(i);
-        if (line_cstr) {
-          current_code.append("\n");
-          current_code.append(line_cstr);
-        }
-      }
-    }
-  }
+  if (current_line_idx < current_lines.GetSize()) {
+      const char *line_cstr = current_lines.GetStringAtIndex(i);
 
   current_code.append("\n");
   current_code += request.GetRawLine();
 
   CompleteCode(current_code, request);
 }
 
 bool QuitCommandOverrideCallback(void *baton, const char **argv) {