Show error codes by default

docs/source/command_line.rst

@@ -703,9 +703,9 @@ in error messages.
     ``file:line:column:end_line:end_column``. This option implies
     ``--show-column-numbers``.
 
-.. option:: --show-error-codes
+.. option:: --hide-error-codes
 
-    This flag will add an error code ``[<code>]`` to error messages. The error
+    This flag will hide the error code ``[<code>]`` from error messages. By default, the error
     code is shown after each error message::
 
         prog.py:1: error: "str" has no attribute "trim"  [attr-defined]

docs/source/config_file.rst

@@ -714,12 +714,12 @@ These options may only be set in the global section (``[mypy]``).
 
     Shows column numbers in error messages.
 
-.. confval:: show_error_codes
+.. confval:: hide_error_codes
 
     :type: boolean
     :default: False
 
-    Shows error codes in error messages. See :ref:`error-codes` for more information.
+    Hide error codes in error messages. See :ref:`error-codes` for more information.
 
 .. confval:: pretty
 

docs/source/error_codes.rst

@@ -23,12 +23,12 @@ Error codes may change in future mypy releases.
 Displaying error codes
 ----------------------
 
-Error codes are not displayed by default.  Use :option:`--show-error-codes <mypy --show-error-codes>`
-or config ``show_error_codes = True`` to display error codes. Error codes are shown inside square brackets:
+Error codes are displayed by default.  Use :option:`--hide-error-codes <mypy --hide-error-codes>`
+or config ``hide_error_codes = True`` to hide error codes. Error codes are shown inside square brackets:
 
 .. code-block:: text
 
-   $ mypy --show-error-codes prog.py
+   $ mypy prog.py
    prog.py:1: error: "str" has no attribute "trim"  [attr-defined]
 
 It's also possible to require error codes for ``type: ignore`` comments.

docs/source/type_inference_and_annotations.rst

@@ -230,8 +230,7 @@ short explanation of the bug. To do that, use this format:
     app.run(8000)  # type: ignore  # `run()` now accepts an `int`, as a port
 
 
-Mypy displays an error code for each error if you use
-:option:`--show-error-codes <mypy --show-error-codes>`:
+By default, mypy displays an error code for each error:
 
 .. code-block:: text
 

mypy/build.py

@@ -230,7 +230,7 @@ def _build(
     errors = Errors(
         options.show_error_context,
         options.show_column_numbers,
-        options.show_error_codes,
+        options.hide_error_codes,
         options.pretty,
         options.show_error_end,
         lambda path: read_py_file(path, cached_read),

mypy/config_parser.py

@@ -434,6 +434,9 @@ def parse_section(
                 elif key.startswith("disallow") and hasattr(template, key[3:]):
                     options_key = key[3:]
                     invert = True
+                elif key.startswith("show_") and hasattr(template, "hide_" + key[5:]):
+                    options_key = "hide_" + key[5:]
+                    invert = True
                 elif key == "strict":
                     pass  # Special handling below
                 else:

mypy/dmypy_server.py

@@ -197,7 +197,7 @@ def __init__(self, options: Options, status_file: str, timeout: int | None = Non
 
         # Since the object is created in the parent process we can check
         # the output terminal options here.
-        self.formatter = FancyFormatter(sys.stdout, sys.stderr, options.show_error_codes)
+        self.formatter = FancyFormatter(sys.stdout, sys.stderr, options.hide_error_codes)
 
     def _response_metadata(self) -> dict[str, str]:
         py_version = f"{self.options.python_version[0]}_{self.options.python_version[1]}"

mypy/errors.py

@@ -257,7 +257,7 @@ def __init__(
         self,
         show_error_context: bool = False,
         show_column_numbers: bool = False,
-        show_error_codes: bool = False,
+        hide_error_codes: bool = False,
         pretty: bool = False,
         show_error_end: bool = False,
         read_source: Callable[[str], list[str] | None] | None = None,
@@ -267,7 +267,7 @@ def __init__(
     ) -> None:
         self.show_error_context = show_error_context
         self.show_column_numbers = show_column_numbers
-        self.show_error_codes = show_error_codes
+        self.hide_error_codes = hide_error_codes
         self.show_absolute_path = show_absolute_path
         self.pretty = pretty
         self.show_error_end = show_error_end
@@ -776,7 +776,7 @@ def format_messages(
                 s = f"{srcloc}: {severity}: {message}"
             else:
                 s = message
-            if self.show_error_codes and code and severity != "note":
+            if not self.hide_error_codes and code and severity != "note":
                 # If note has an error code, it is related to a previous error. Avoid
                 # displaying duplicate error codes.
                 s = f"{s}  [{code.code}]"

mypy/main.py

@@ -67,7 +67,7 @@ def main(
     if clean_exit:
         options.fast_exit = False
 
-    formatter = util.FancyFormatter(stdout, stderr, options.show_error_codes)
+    formatter = util.FancyFormatter(stdout, stderr, options.hide_error_codes)
 
     if options.install_types and (stdout is not sys.stdout or stderr is not sys.stderr):
         # Since --install-types performs user input, we want regular stdout and stderr.
@@ -151,7 +151,7 @@ def run_build(
     stdout: TextIO,
     stderr: TextIO,
 ) -> tuple[build.BuildResult | None, list[str], bool]:
-    formatter = util.FancyFormatter(stdout, stderr, options.show_error_codes)
+    formatter = util.FancyFormatter(stdout, stderr, options.hide_error_codes)
 
     messages = []
 
@@ -871,9 +871,9 @@ def add_invertible_flag(
         group=error_group,
     )
     add_invertible_flag(
-        "--show-error-codes",
+        "--hide-error-codes",
         default=False,
-        help="Show error codes in error messages",
+        help="Hide error codes in error messages",
         group=error_group,
     )
     add_invertible_flag(

mypy/options.py

@@ -274,7 +274,7 @@ def __init__(self) -> None:
         self.shadow_file: list[list[str]] | None = None
         self.show_column_numbers: bool = False
         self.show_error_end: bool = False
-        self.show_error_codes = False
+        self.hide_error_codes = False
         # Use soft word wrap and show trimmed source snippets with error location markers.
         self.pretty = False
         self.dump_graph = False

mypy/test/helpers.py

@@ -363,7 +363,7 @@ def parse_options(
             flags = flags2
 
     if flags:
-        flag_list = flags.group(1).split()
+        flag_list = ["--hide-error-codes", *flags.group(1).split()]
         flag_list.append("--no-site-packages")  # the tests shouldn't need an installed Python
         targets, options = process_options(flag_list, require_targets=False)
         if targets:
@@ -375,6 +375,7 @@ def parse_options(
         # TODO: Enable strict optional in test cases by default (requires *many* test case changes)
         options.strict_optional = False
         options.error_summary = False
+        options.hide_error_codes = True
 
     # Allow custom python version to override testfile_pyversion.
     if all(flag.split("=")[0] not in ["--python-version", "-2", "--py2"] for flag in flag_list):

mypy/test/testcheck.py

@@ -119,7 +119,7 @@ def run_case_once(
         if "columns" in testcase.file:
             options.show_column_numbers = True
         if "errorcodes" in testcase.file:
-            options.show_error_codes = True
+            options.hide_error_codes = False
 
         if incremental_step and options.incremental:
             # Don't overwrite # flags: --no-incremental in incremental test cases

mypy/util.py

@@ -522,8 +522,8 @@ class FancyFormatter:
     This currently only works on Linux and Mac.
     """
 
-    def __init__(self, f_out: IO[str], f_err: IO[str], show_error_codes: bool) -> None:
-        self.show_error_codes = show_error_codes
+    def __init__(self, f_out: IO[str], f_err: IO[str], hide_error_codes: bool) -> None:
+        self.hide_error_codes = hide_error_codes
         # Check if we are in a human-facing terminal on a supported platform.
         if sys.platform not in ("linux", "darwin", "win32"):
             self.dummy_term = True
@@ -681,7 +681,7 @@ def colorize(self, error: str) -> str:
         """Colorize an output line by highlighting the status and error code."""
         if ": error:" in error:
             loc, msg = error.split("error:", maxsplit=1)
-            if not self.show_error_codes:
+            if self.hide_error_codes:
                 return (
                     loc + self.style("error:", "red", bold=True) + self.highlight_quote_groups(msg)
                 )

mypy_self_check.ini

@@ -5,7 +5,6 @@ warn_no_return = True
 strict_optional = True
 disallow_any_unimported = True
 show_traceback = True
-show_error_codes = True
 pretty = True
 always_false = MYPYC
 plugins = misc/proper_plugin.py