Make deprecated Note a standard Error, disabled by default

While working on the relase of mypy 1.14 we noticed a large number of
notes for deprecated. Speaking with Jukka, he suggested we make this
disabled by default. And if it's disabled by default, having it as a
note is not as useful. We also don't have many stand alone notes. Most
notes are "attached" with an error.

This PR makes the deprecated error disabled by default, removes the flag
to report it as error and always reports it as error when enabled.

Author: svalentin

docs/source/command_line.rst

@@ -537,12 +537,6 @@ potentially problematic or redundant in some way.
 
         This limitation will be removed in future releases of mypy.
 
-.. option:: --report-deprecated-as-error
-
-    By default, mypy emits notes if your code imports or uses deprecated
-    features.    This flag converts such notes to errors, causing mypy to
-    eventually finish with a non-zero exit code.  Features are considered
-    deprecated when decorated with ``warnings.deprecated``.
 
 .. _miscellaneous-strictness-flags:
 

docs/source/error_code_list2.rst

@@ -236,13 +236,12 @@ incorrect control flow or conditional checks that are accidentally always true o
 Check that imported or used feature is deprecated [deprecated]
 --------------------------------------------------------------
 
-By default, mypy generates a note if your code imports a deprecated feature explicitly with a
+If you use :option:`--enable-error-code deprecated <mypy --enable-error-code>`,
+mypy generates an error if your code imports a deprecated feature explicitly with a
 ``from mod import depr`` statement or uses a deprecated feature imported otherwise or defined
 locally.  Features are considered deprecated when decorated with ``warnings.deprecated``, as
-specified in `PEP 702 <https://peps.python.org/pep-0702>`_.  You can silence single notes via
+specified in `PEP 702 <https://peps.python.org/pep-0702>`_.  You can silence single errors via
 ``# type: ignore[deprecated]`` or turn off this check completely via ``--disable-error-code=deprecated``.
-Use the :option:`--report-deprecated-as-error <mypy --report-deprecated-as-error>` option for
-more strictness, which turns all such notes into errors.
 
 .. note::
 

mypy/checker.py

@@ -7696,8 +7696,7 @@ def warn_deprecated(self, node: SymbolNode | None, context: Context) -> None:
             and ((deprecated := node.deprecated) is not None)
             and not self.is_typeshed_stub
         ):
-            warn = self.msg.fail if self.options.report_deprecated_as_error else self.msg.note
-            warn(deprecated, context, code=codes.DEPRECATED)
+            self.msg.fail(deprecated, context, code=codes.DEPRECATED)
 
 
 class CollectArgTypeVarTypes(TypeTraverserVisitor):

mypy/errorcodes.py

@@ -308,6 +308,7 @@ def __hash__(self) -> int:
     "deprecated",
     "Warn when importing or using deprecated (overloaded) functions, methods or classes",
     "General",
+    default_enabled=False,
 )
 
 # This copy will not include any error codes defined later in the plugins.

mypy/errors.py

@@ -20,7 +20,7 @@
 
 # Show error codes for some note-level messages (these usually appear alone
 # and not as a comment for a previous error-level message).
-SHOW_NOTE_CODES: Final = {codes.ANNOTATION_UNCHECKED, codes.DEPRECATED}
+SHOW_NOTE_CODES: Final = {codes.ANNOTATION_UNCHECKED}
 
 # Do not add notes with links to error code docs to errors with these codes.
 # We can tweak this set as we get more experience about what is helpful and what is not.

mypy/main.py

@@ -804,13 +804,6 @@ def add_invertible_flag(
         help="Warn about statements or expressions inferred to be unreachable",
         group=lint_group,
     )
-    add_invertible_flag(
-        "--report-deprecated-as-error",
-        default=False,
-        strict_flag=False,
-        help="Report importing or using deprecated features as errors instead of notes",
-        group=lint_group,
-    )
 
     # Note: this group is intentionally added here even though we don't add
     # --strict to this group near the end.

mypy/options.py

@@ -173,9 +173,6 @@ def __init__(self) -> None:
         # declared with a precise type
         self.warn_return_any = False
 
-        # Report importing or using deprecated features as errors instead of notes.
-        self.report_deprecated_as_error = False
-
         # Warn about unused '# type: ignore' comments
         self.warn_unused_ignores = False
 

mypy/typeanal.py

@@ -790,8 +790,7 @@ def check_and_warn_deprecated(self, info: TypeInfo, ctx: Context) -> None:
                 if isinstance(imp, ImportFrom) and any(info.name == n[0] for n in imp.names):
                     break
             else:
-                warn = self.fail if self.options.report_deprecated_as_error else self.note
-                warn(deprecated, ctx, code=codes.DEPRECATED)
+                self.fail(deprecated, ctx, code=codes.DEPRECATED)
 
     def analyze_type_with_type_info(
         self, info: TypeInfo, args: Sequence[Type], ctx: Context, empty_tuple_index: bool