Enable --pretty by default for better error messages

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
 

mypy/main.py

@@ -1007,7 +1007,7 @@ def add_invertible_flag(
     )
     add_invertible_flag(
         "--pretty",
-        default=False,
+        default=True,
         help="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

mypy/test/helpers.py

@@ -352,11 +352,14 @@ def parse_options(
             raise RuntimeError("Specifying targets via the flags pragma is not supported.")
         if "--show-error-codes" not in flag_list:
             options.hide_error_codes = True
+        if "--pretty" not in flag_list:
+            options.pretty = False
     else:
         flag_list = []
         options = Options()
         options.error_summary = False
         options.hide_error_codes = True
+        options.pretty = False
 
     # Allow custom python version to override testfile_pyversion.
     if all(flag.split("=")[0] != "--python-version" for flag in flag_list):

mypy/test/testcmdline.py

@@ -66,6 +66,8 @@ def test_python_cmdline(testcase: DataDrivenTestCase, step: int) -> None:
         args.append("--hide-error-codes")
     if "--disallow-empty-bodies" not in args:
         args.append("--allow-empty-bodies")
+    if "--pretty" not in args:
+        args.append("--no-pretty")
     # Type check the program.
     fixed = [python3_path, "-m", "mypy"]
     env = os.environ.copy()

mypy/test/testpythoneval.py

@@ -52,6 +52,7 @@ def test_python_evaluation(testcase: DataDrivenTestCase, cache_dir: str) -> None
         "--no-error-summary",
         "--hide-error-codes",
         "--allow-empty-bodies",
+        "--no-pretty",
         "--test-env",  # Speeds up some checks
     ]
     interpreter = python3_path