Temporarily put back --enable-recursive-aliases (as depreceated) (#13852)

The motivation here is to not penalize people who try early features
with breaking their CI. We can delete this flag after one-two releases.

Author: ilevkivskyi

mypy/main.py

@@ -979,6 +979,10 @@ def add_invertible_flag(
         action="store_true",
         help="Disable experimental support for recursive type aliases",
     )
+    # Deprecated reverse variant of the above.
+    internals_group.add_argument(
+        "--enable-recursive-aliases", action="store_true", help=argparse.SUPPRESS
+    )
     parser.add_argument(
         "--enable-incomplete-feature",
         action="append",
@@ -1336,6 +1340,12 @@ def set_strict_flags() -> None:
     if options.logical_deps:
         options.cache_fine_grained = True
 
+    if options.enable_recursive_aliases:
+        print(
+            "Warning: --enable-recursive-aliases is deprecated;"
+            " recursive types are enabled by default"
+        )
+
     # Set target.
     if special_opts.modules + special_opts.packages:
         options.build_type = BuildType.MODULE

mypy/options.py

@@ -326,6 +326,8 @@ def __init__(self) -> None:
         self.many_errors_threshold = defaults.MANY_ERRORS_THRESHOLD
         # Disable recursive type aliases (currently experimental)
         self.disable_recursive_aliases = False
+        # Deprecated reverse version of the above, do not use.
+        self.enable_recursive_aliases = False
 
     # To avoid breaking plugin compatibility, keep providing new_semantic_analyzer
     @property

test-data/unit/cmdline.test

@@ -1476,3 +1476,11 @@ note: A user-defined top-level module with name "typing" is not supported
 [out]
 Failed to find builtin module mypy_extensions, perhaps typeshed is broken?
 == Return code: 2
+
+[case testRecursiveAliasesFlagDeprecated]
+# cmd: mypy --enable-recursive-aliases a.py
+[file a.py]
+pass
+[out]
+Warning: --enable-recursive-aliases is deprecated; recursive types are enabled by default
+== Return code: 0