Enable --pretty by default

This change enables the --pretty option by default, which shows visually
nicer error messages with source code snippets and error location markers.

Users can still use --no-pretty to get the previous concise output format.

Closes #19108

Author: njg7194

docs/source/command_line.rst

@@ -937,6 +937,7 @@ in error messages.
 
     Use visually nicer output in error messages: use soft word wrap,
     show source code snippets, and show error location markers.
+    This is enabled by default. Use ``--no-pretty`` to disable.
 
 .. option:: --no-color-output
 

docs/source/config_file.rst

@@ -904,7 +904,7 @@ These options may only be set in the global section (``[mypy]``).
 .. confval:: pretty
 
     :type: boolean
-    :default: False
+    :default: True
 
     Use visually nicer output in error messages: use soft word wrap,
     show source code snippets, and show error location markers.

mypy/options.py

@@ -365,7 +365,7 @@ def __init__(self) -> None:
         self.hide_error_codes = False
         self.show_error_code_links = False
         # Use soft word wrap and show trimmed source snippets with error location markers.
-        self.pretty = False
+        self.pretty = True
         self.dump_graph = False
         self.dump_deps = False
         self.logical_deps = False