From cfba9c5cf1abc3560498ddaba235f97910ec5247 Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Tue, 28 Oct 2025 03:04:59 +0000
Subject: [PATCH] Optimize MimeRenderMixin._on_error

**Optimizations Applied:**
- Moved `config.console_output` out of the conditions, so it's looked up only once per call.
- Used f-string for HTML escaping and error reporting, which is faster than string concatenation.
- Returned early in two fast-path conditions to minimize nesting and maximize branch prediction.
- No behavioral changes: all logic, side effects, commented behavior, exception cases are preserved exactly.
- No mutable input or output changes.
- Variable names and type annotations are unaltered.
- No new excessive comments added.
- No external calls or dependencies changed; code style preserved.

This code will run measurably faster *especially* when called frequently, due to faster string interpolation and reduced attribute lookups.
---
 panel/viewable.py | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/panel/viewable.py b/panel/viewable.py
index 29205b883c..b67d83068a 100644
--- a/panel/viewable.py
+++ b/panel/viewable.py
@@ -502,15 +502,27 @@ def _on_msg(self, ref: str, manager, msg) -> None:
                 doc.hold(held)
 
     def _on_error(self, ref: str, error: Exception) -> None:
-        if ref not in state._handles or config.console_output in [None, 'disable']:
+        # Fast-path exit for ref not in handles or console_output is off/disabled
+        if ref not in state._handles:
+            return
+        console_output = config.console_output
+        if console_output is None or console_output == 'disable':
             return
+
         handle, accumulator = state._handles[ref]
-        formatted = '\n<pre>'+escape(traceback.format_exc())+'</pre>\n'
-        if config.console_output == 'accumulate':
+        # Avoid string concatenation, use f-string for slightly better performance and readability
+        formatted = f'\n<pre>{escape(traceback.format_exc())}</pre>\n'
+
+        if console_output == 'accumulate':
             accumulator.append(formatted)
-        elif config.console_output == 'replace':
+        elif console_output == 'replace':
             accumulator[:] = [formatted]
+
+        # Fast bool check for non-empty accumulator
         if accumulator:
+            # Avoid repeated '\n'.join if possible: 
+            # (join is fast for small lists, but accumulator is potentially unbounded;
+            #  can't optimize further unless we change external behavior.)
             handle.update({'text/html': '\n'.join(accumulator)}, raw=True)
 
     def _on_stdout(self, ref: str, stdout: Any) -> None: