move a bunch of imports into TYPE_CHECKING blocks

These are only used for type checking, so don't bother importing them at
runtime.

Generally add future annotations at the same time, to make sure that
existing uses of these imports don't need to be quoted.

mesonbuild/dependencies/pkgconfig.py

@@ -11,9 +11,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 
 from .base import ExternalDependency, DependencyException, sort_libpaths, DependencyTypeName
-from ..mesonlib import MachineChoice, OptionKey, OrderedSet, PerMachine, Popen_safe
+from ..mesonlib import OptionKey, OrderedSet, PerMachine, Popen_safe
 from ..programs import find_external_program, ExternalProgram
 from .. import mlog
 from pathlib import PurePath
@@ -24,6 +25,7 @@ import typing as T
 
 if T.TYPE_CHECKING:
     from ..environment import Environment
+    from ..mesonlib import MachineChoice
     from .._typing import ImmutableListProtocol
 
 class PkgConfigDependency(ExternalDependency):

mesonbuild/interpreter/interpreter.py

@@ -33,10 +33,9 @@ from ..interpreterbase import InterpreterException, InvalidArguments, InvalidCod
 from ..interpreterbase import Disabler, disablerIfNotFound
 from ..interpreterbase import FeatureNew, FeatureDeprecated, FeatureNewKwargs, FeatureDeprecatedKwargs
 from ..interpreterbase import ObjectHolder
-from ..interpreterbase.baseobjects import InterpreterObject, TYPE_var, TYPE_kwargs
 from ..modules import ExtensionModule, ModuleObject, MutableModuleObject, NewExtensionModule, NotFoundExtensionModule
 from ..cmake import CMakeInterpreter
-from ..backend.backends import Backend, ExecutableSerialisation
+from ..backend.backends import ExecutableSerialisation
 
 from . import interpreterobjects as OBJ
 from . import compiler as compilerOBJ
@@ -96,6 +95,8 @@ if T.TYPE_CHECKING:
     from typing_extensions import Literal
 
     from . import kwargs
+    from ..backend.backends import Backend
+    from ..interpreterbase.baseobjects import InterpreterObject, TYPE_var, TYPE_kwargs
     from ..programs import OverrideProgram
 
     # Input source types passed to Targets

mesonbuild/interpreter/primitives/array.py

@@ -1,5 +1,6 @@
 # Copyright 2021 The Meson development team
 # SPDX-license-identifier: Apache-2.0
+from __future__ import annotations
 
 import typing as T
 
@@ -15,7 +16,6 @@ from ...interpreterbase import (
     FeatureNew,
 
     TYPE_var,
-    TYPE_kwargs,
 
     InvalidArguments,
 )
@@ -24,6 +24,7 @@ from ...mparser import PlusAssignmentNode
 if T.TYPE_CHECKING:
     # Object holders need the actual interpreter
     from ...interpreter import Interpreter
+    from ...interpreterbase import TYPE_kwargs
 
 class ArrayHolder(ObjectHolder[T.List[TYPE_var]], IterableObject):
     def __init__(self, obj: T.List[TYPE_var], interpreter: 'Interpreter') -> None:

mesonbuild/interpreter/primitives/dict.py

@@ -1,5 +1,6 @@
 # Copyright 2021 The Meson development team
 # SPDX-license-identifier: Apache-2.0
+from __future__ import annotations
 
 import typing as T
 
@@ -14,7 +15,6 @@ from ...interpreterbase import (
     typed_pos_args,
 
     TYPE_var,
-    TYPE_kwargs,
 
     InvalidArguments,
 )
@@ -22,6 +22,7 @@ from ...interpreterbase import (
 if T.TYPE_CHECKING:
     # Object holders need the actual interpreter
     from ...interpreter import Interpreter
+    from ...interpreterbase import TYPE_kwargs
 
 class DictHolder(ObjectHolder[T.Dict[str, TYPE_var]], IterableObject):
     def __init__(self, obj: T.Dict[str, TYPE_var], interpreter: 'Interpreter') -> None:

mesonbuild/interpreter/primitives/integer.py

@@ -1,5 +1,6 @@
 # Copyright 2021 The Meson development team
 # SPDX-license-identifier: Apache-2.0
+from __future__ import annotations
 
 from ...interpreterbase import (
     ObjectHolder,
@@ -8,9 +9,6 @@ from ...interpreterbase import (
     noKwargs,
     noPosargs,
 
-    TYPE_var,
-    TYPE_kwargs,
-
     InvalidArguments
 )
 
@@ -19,6 +17,7 @@ import typing as T
 if T.TYPE_CHECKING:
     # Object holders need the actual interpreter
     from ...interpreter import Interpreter
+    from ...interpreterbase import TYPE_var, TYPE_kwargs
 
 class IntegerHolder(ObjectHolder[int]):
     def __init__(self, obj: int, interpreter: 'Interpreter') -> None:

mesonbuild/interpreter/primitives/string.py

@@ -1,5 +1,6 @@
 # Copyright 2021 The Meson development team
 # SPDX-license-identifier: Apache-2.0
+from __future__ import annotations
 
 import re
 import os
@@ -17,9 +18,6 @@ from ...interpreterbase import (
     noPosargs,
     typed_pos_args,
 
-    TYPE_var,
-    TYPE_kwargs,
-
     InvalidArguments,
 )
 
@@ -27,6 +25,7 @@ from ...interpreterbase import (
 if T.TYPE_CHECKING:
     # Object holders need the actual interpreter
     from ...interpreter import Interpreter
+    from ...interpreterbase import TYPE_var, TYPE_kwargs
 
 class StringHolder(ObjectHolder[str]):
     def __init__(self, obj: str, interpreter: 'Interpreter') -> None:

mesonbuild/interpreter/type_checking.py

@@ -11,7 +11,6 @@ from .. import compilers
 from ..build import (EnvironmentVariables, EnvInitValueType, CustomTarget, BuildTarget,
                      CustomTargetIndex, ExtractedObjects, GeneratedList, IncludeDirs)
 from ..coredata import UserFeatureOption
-from ..interpreterbase import TYPE_var
 from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo
 from ..mesonlib import File, FileMode, MachineChoice, listify, has_path_sep, OptionKey
 from ..programs import ExternalProgram
@@ -22,6 +21,8 @@ NoneType: T.Type[None] = type(None)
 if T.TYPE_CHECKING:
     from typing_extensions import Literal
 
+    from ..interpreterbase import TYPE_var
+
 def in_set_validator(choices: T.Set[str]) -> T.Callable[[str], T.Optional[str]]:
     """Check that the choice given was one of the given set."""
 

mesonbuild/interpreterbase/decorators.py

@@ -11,12 +11,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 
 from .. import mesonlib, mlog
-from .baseobjects import TV_func, TYPE_var, TYPE_kwargs
 from .disabler import Disabler
 from .exceptions import InterpreterException, InvalidArguments
-from .operator import MesonOperator
 from ._unholder import _unholder
 
 from dataclasses import dataclass
@@ -30,8 +29,9 @@ if T.TYPE_CHECKING:
     from typing_extensions import Protocol
 
     from .. import mparser
-    from .baseobjects import InterpreterObject
+    from .baseobjects import InterpreterObject, TV_func, TYPE_var, TYPE_kwargs
     from .interpreterbase import SubProject
+    from .operator import MesonOperator
 
     _TV_IntegerObject = T.TypeVar('_TV_IntegerObject', bound=InterpreterObject, contravariant=True)
     _TV_ARG1 = T.TypeVar('_TV_ARG1', bound=TYPE_var, contravariant=True)

mesonbuild/interpreterbase/disabler.py

@@ -11,10 +11,15 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 
-from .baseobjects import MesonInterpreterObject, TYPE_var, TYPE_kwargs
 import typing as T
 
+from .baseobjects import MesonInterpreterObject
+
+if T.TYPE_CHECKING:
+    from .baseobjects import TYPE_var, TYPE_kwargs
+
 class Disabler(MesonInterpreterObject):
     def method_call(self, method_name: str, args: T.List[TYPE_var], kwargs: TYPE_kwargs) -> TYPE_var:
         if method_name == 'found':

mesonbuild/interpreterbase/interpreterbase.py

@@ -14,6 +14,7 @@
 
 # This class contains the basic functionality needed to run any interpreter
 # or an interpreter-based tool.
+from __future__ import annotations
 
 from .. import mparser, mesonlib
 from .. import environment
@@ -26,10 +27,7 @@ from .baseobjects import (
     ObjectHolder,
     IterableObject,
 
-    SubProject,
-
     TYPE_var,
-    TYPE_kwargs,
 
     HoldableTypes,
 )
@@ -54,6 +52,7 @@ import typing as T
 import textwrap
 
 if T.TYPE_CHECKING:
+    from .baseobjects import SubProject, TYPE_kwargs
     from ..interpreter import Interpreter
 
 HolderMapType = T.Dict[

mesonbuild/linkers/detect.py

@@ -12,14 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 from ..mesonlib import (
-    EnvironmentException, MachineChoice, OptionKey,
+    EnvironmentException, OptionKey,
     Popen_safe, search_version
 )
 from .linkers import (
-    DynamicLinker,
     AppleDynamicLinker,
-    GnuDynamicLinker,
     GnuGoldDynamicLinker,
     GnuBFDDynamicLinker,
     LLVMDynamicLinker,
@@ -36,8 +36,10 @@ import shlex
 import typing as T
 
 if T.TYPE_CHECKING:
+    from .linkers import DynamicLinker, GnuDynamicLinker
     from ..environment import Environment
     from ..compilers import Compiler
+    from ..mesonlib import MachineChoice
 
 defaults: T.Dict[str, T.List[str]] = {}
 defaults['static_linker'] = ['ar', 'gar']