[lldb] Add indentation scope guard

Add `IndentScope Stream::MakeIndentScope()` to
make managing (and restoring!) of the indentation
level on `Stream` instances more ergonomic and
less error prone.

Author: yln

lldb/include/lldb/Utility/Stream.h

@@ -300,6 +300,12 @@ class Stream {
   ///     The current indentation level.
   unsigned GetIndentLevel() const;
 
+  /// Set the current indentation level.
+  ///
+  /// \param[in] level
+  ///     The new indentation level.
+  void SetIndentLevel(unsigned level);
+
   /// Indent the current line in the stream.
   ///
   /// Indent the current line using the current indentation level and print an
@@ -315,6 +321,20 @@ class Stream {
   /// Increment the current indentation level.
   void IndentMore(unsigned amount = 2);
 
+  class IndentScope {
+    Stream &m_stream;
+    unsigned m_original_indent_level;
+
+  public:
+    IndentScope(Stream &stream)
+        : m_stream(stream), m_original_indent_level(stream.GetIndentLevel()) {}
+    ~IndentScope() { m_stream.SetIndentLevel(m_original_indent_level); }
+  };
+
+  /// Create an indentation scope that restores the original indent level when
+  /// the object goes out of scope (RAII).
+  IndentScope MakeIndentScope(unsigned indent_amount = 2);
+
   /// Output an offset value.
   ///
   /// Put an offset \a uval out to the stream using the printf format in \a
@@ -364,12 +384,6 @@ class Stream {
   ///     address and pointer values.
   void SetAddressByteSize(uint32_t addr_size);
 
-  /// Set the current indentation level.
-  ///
-  /// \param[in] level
-  ///     The new indentation level.
-  void SetIndentLevel(unsigned level);
-
   /// Output a SLEB128 number to the stream.
   ///
   /// Put an SLEB128 \a uval out to the stream using the printf format in \a

lldb/source/Utility/Stream.cpp

@@ -202,6 +202,14 @@ void Stream::IndentLess(unsigned amount) {
     m_indent_level = 0;
 }
 
+// Create an indentation scope that restores the original indent level when the
+// object goes out of scope (RAII).
+Stream::IndentScope Stream::MakeIndentScope(unsigned indent_amount) {
+  IndentScope indent_scope(*this);
+  IndentMore(indent_amount);
+  return indent_scope;
+}
+
 // Get the address size in bytes
 uint32_t Stream::GetAddressByteSize() const { return m_addr_size; }