From 3a17a762334d9a45106321ef5dfdc43ffb848ed1 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Tue, 16 May 2023 21:34:34 +0100
Subject: [PATCH] Exit debug (#2554)

* show single error by default

* changelog

* show numbers of errors

* changelog
---
 CHANGELOG.md       |  1 +
 src/textual/app.py | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 145e578a2..cd3e91dda 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - App `title` and `sub_title` attributes can be set to any type https://github.com/Textualize/textual/issues/2521
+- Only a single error will be written by default, unless in dev mode ("debug" in App.features) https://github.com/Textualize/textual/issues/2480
 - Using `Widget.move_child` where the target and the child being moved are the same is now a no-op https://github.com/Textualize/textual/issues/1743
 - Calling `dismiss` on a screen that is not at the top of the stack now raises an exception https://github.com/Textualize/textual/issues/2575
 - `MessagePump.call_after_refresh` and `MessagePump.call_later` will not return `False` if the callback could not be scheduled. https://github.com/Textualize/textual/pull/2584
diff --git a/src/textual/app.py b/src/textual/app.py
index 841d854e2..c8863d764 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -1630,8 +1630,22 @@ class App(Generic[ReturnType], DOMNode):
 
     def _print_error_renderables(self) -> None:
         """Print and clear exit renderables."""
-        for renderable in self._exit_renderables:
-            self.error_console.print(renderable)
+        error_count = len(self._exit_renderables)
+        if "debug" in self.features:
+            for renderable in self._exit_renderables:
+                self.error_console.print(renderable)
+            if error_count > 1:
+                self.error_console.print(
+                    f"\n[b]NOTE:[/b] {error_count} errors show above.", markup=True
+                )
+        elif self._exit_renderables:
+            self.error_console.print(self._exit_renderables[0])
+            if error_count > 1:
+                self.error_console.print(
+                    f"\n[b]NOTE:[/b] 1 of {error_count} errors show. Run with [b]--dev[/] to see all errors.",
+                    markup=True,
+                )
+
         self._exit_renderables.clear()
 
     async def _process_messages(