Refuse modification of ReadOnly buffers and make Debug buffer readonly

The debug buffer is a bit special as lots of events might mutate it,
permitting it to be modified leads to some buggy behaviour:

For example, `pipe` uses a ForwardChangeTracker to track buffer
changes, but when applied on a debug buffer with the profile flag
on, each shell execution will trigger an additional modification
of the buffer while applying the changes, leading to an assertion
failing as changes might not be happening in a forward way anymore.

Trying to modify a debug buffer will now raise an error immediatly.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/buffer_utils.cc b/src/buffer_utils.cc
index 1e282695..4a6e3816 100644
--- a/src/buffer_utils.cc
+++ b/src/buffer_utils.cc
@@ -181,12 +181,17 @@ void write_to_debug_buffer(StringView str)
     // where the user can put its cursor to scroll with new messages
     const bool eol_back = not str.empty() and str.back() == '\n';
     if (Buffer* buffer = BufferManager::instance().get_buffer_ifp(debug_buffer_name))
+    {
+        buffer->flags() &= ~Buffer::Flags::ReadOnly;
+        auto restore = on_scope_end([buffer] { buffer->flags() |= Buffer::Flags::ReadOnly; });
+
         buffer->insert(buffer->back_coord(), eol_back ? str : str + "\n");
+    }
     else
     {
         String line = str + (eol_back ? "\n" : "\n\n");
         BufferManager::instance().create_buffer(
-            debug_buffer_name.str(), Buffer::Flags::NoUndo | Buffer::Flags::Debug,
+            debug_buffer_name.str(), Buffer::Flags::NoUndo | Buffer::Flags::Debug | Buffer::Flags::ReadOnly,
             line, InvalidTime);
     }
 }