interpreter: simplify and export env validator/convertor

mypy is now able to deal with extra optional arguments.
Also export env_validator instead of fishing it out of ENV_KW.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/interpreter/interpreter.py

diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index 707e856..fa8ee55 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -98,7 +98,8 @@
     TEST_KWS,
     NoneType,
     in_set_validator,
-    env_convertor_with_method
+    env_convertor,
+    env_validator,
 )
 from . import primitives as P_OBJ
 
@@ -3226,13 +3227,13 @@
         init = args[0]
         if init is not None:
             FeatureNew.single_use('environment positional arguments', '0.52.0', self.subproject, location=node)
-            msg = ENV_KW.validator(init)
+            msg = env_validator(init)
             if msg:
                 raise InvalidArguments(f'"environment": {msg}')
             if isinstance(init, dict) and any(i for i in init.values() if isinstance(i, list)):
                 FeatureNew.single_use('List of string in dictionary value', '0.62.0', self.subproject, location=node)
             # the validator call above ensured that we have the correct type
-            return env_convertor_with_method(T.cast('FullEnvInitValueType', init), kwargs['method'], kwargs['separator'])
+            return env_convertor(T.cast('FullEnvInitValueType', init), kwargs['method'], kwargs['separator'])
         return EnvironmentVariables()
 
     @typed_pos_args('join_paths', varargs=str, min_varargs=1)

mesonbuild/interpreter/mesonmain.py

diff --git a/mesonbuild/interpreter/mesonmain.py b/mesonbuild/interpreter/mesonmain.py
index 9501131..c1436ed 100644
--- a/mesonbuild/interpreter/mesonmain.py
+++ b/mesonbuild/interpreter/mesonmain.py
@@ -15,13 +15,13 @@
 from ..mesonlib import MachineChoice
 from ..options import OptionKey
 from ..programs import Program, ExternalProgram
-from ..interpreter.type_checking import ENV_KW, ENV_METHOD_KW, ENV_SEPARATOR_KW, env_convertor_with_method
+from ..interpreter.type_checking import ENV_METHOD_KW, ENV_SEPARATOR_KW, env_convertor
 from ..interpreterbase import (MesonInterpreterObject, FeatureNew, FeatureDeprecated, FeatureBroken,
                                typed_pos_args,  noArgsFlattening, noPosargs, noKwargs,
                                typed_kwargs, KwargInfo, InterpreterException, InterpreterObject)
 from .decorators import apply_machine_map
 from .primitives import MesonVersionString
-from .type_checking import NATIVE_KW, NoneType
+from .type_checking import NATIVE_KW, NoneType, env_validator
 
 if T.TYPE_CHECKING:
     from typing_extensions import Literal, TypedDict
@@ -488,10 +488,10 @@
     def add_devenv_method(self, args: T.Tuple[T.Union[str, list, dict, mesonlib.EnvironmentVariables]],
                           kwargs: 'AddDevenvKW') -> None:
         env = args[0]
-        msg = ENV_KW.validator(env)
+        msg = env_validator(env)
         if msg:
             raise build.InvalidArguments(f'"add_devenv": {msg}')
-        converted = env_convertor_with_method(env, kwargs['method'], kwargs['separator'])
+        converted = env_convertor(env, kwargs['method'], kwargs['separator'])
         assert isinstance(converted, mesonlib.EnvironmentVariables)
         self.build.devenv.append(converted)
 

mesonbuild/interpreter/type_checking.py

diff --git a/mesonbuild/interpreter/type_checking.py b/mesonbuild/interpreter/type_checking.py
index 03bf408..6f255db 100644
--- a/mesonbuild/interpreter/type_checking.py
+++ b/mesonbuild/interpreter/type_checking.py
@@ -196,8 +196,8 @@
 
 DISABLER_KW: KwargInfo[bool] = KwargInfo('disabler', bool, default=False)
 
-def _env_validator(value: T.Union[EnvironmentVariables, T.List['TYPE_var'], T.Dict[str, 'TYPE_var'], str, None],
-                   only_dict_str: bool = True) -> T.Optional[str]:
+def env_validator(value: T.Union[EnvironmentVariables, T.List['TYPE_var'], T.Dict[str, 'TYPE_var'], str, None],
+                  only_dict_str: bool = True) -> T.Optional[str]:
     def _splitter(v: str) -> T.Optional[str]:
         split = v.split('=', 1)
         if len(split) == 1:
@@ -232,7 +232,7 @@
 
 def _options_validator(value: T.Union[EnvironmentVariables, T.List['TYPE_var'], T.Dict[str, 'TYPE_var'], str, None]) -> T.Optional[str]:
     # Reusing the env validator is a little overkill, but nicer than duplicating the code
-    return _env_validator(value, only_dict_str=False)
+    return env_validator(value, only_dict_str=False)
 
 def split_equal_string(input: str) -> T.Tuple[str, str]:
     """Split a string in the form `x=y`
@@ -242,11 +242,9 @@
     a, b = input.split('=', 1)
     return (a, b)
 
-# Split _env_convertor() and env_convertor_with_method() to make mypy happy.
-# It does not want extra arguments in KwargInfo convertor callable.
-def env_convertor_with_method(value: FullEnvInitValueType,
-                              init_method: Literal['set', 'prepend', 'append'] = 'set',
-                              separator: str = os.pathsep) -> EnvironmentVariables:
+def env_convertor(value: FullEnvInitValueType,
+                  init_method: Literal['set', 'prepend', 'append'] = 'set',
+                  separator: str = os.pathsep) -> EnvironmentVariables:
     if isinstance(value, str):
         return EnvironmentVariables(dict([split_equal_string(value)]), init_method, separator)
     elif isinstance(value, list):
@@ -257,14 +255,11 @@
         return EnvironmentVariables()
     return value
 
-def _env_convertor(value: FullEnvInitValueType) -> EnvironmentVariables:
-    return env_convertor_with_method(value)
-
 ENV_KW: KwargInfo[T.Union[EnvironmentVariables, T.List, T.Dict, str, None]] = KwargInfo(
     'env',
     (EnvironmentVariables, list, dict, str, NoneType),
-    validator=_env_validator,
-    convertor=_env_convertor,
+    validator=env_validator,
+    convertor=env_convertor,
 )
 
 DEPFILE_KW: KwargInfo[T.Optional[str]] = KwargInfo(