clean up function signatures in preparation for dataclasses

FeatureCheck always immediately sets extra_message to '' if it isn't
explicitly passed, so there is really no point in using None as a
sentinel that is never used.

Names used in init functions are sometimes pointlessly different from
the class instance attributes they are immediately assigned to. They
would make more sense if defined properly.

mesonbuild/build.py

@@ -139,12 +139,12 @@ class DependencyOverride(HoldableObject):
 class Headers(HoldableObject):
 
     def __init__(self, sources: T.List[File], install_subdir: T.Optional[str],
-                 install_dir: T.Optional[str], install_mode: 'FileMode',
+                 custom_install_dir: T.Optional[str], custom_install_mode: 'FileMode',
                  subproject: str):
         self.sources = sources
         self.install_subdir = install_subdir
-        self.custom_install_dir = install_dir
-        self.custom_install_mode = install_mode
+        self.custom_install_dir = custom_install_dir
+        self.custom_install_mode = custom_install_mode
         self.subproject = subproject
 
     # TODO: we really don't need any of these methods, but they're preserved to
@@ -168,12 +168,12 @@ class Headers(HoldableObject):
 
 class Man(HoldableObject):
 
-    def __init__(self, sources: T.List[File], install_dir: T.Optional[str],
-                 install_mode: 'FileMode', subproject: str,
+    def __init__(self, sources: T.List[File], custom_install_dir: T.Optional[str],
+                 custom_install_mode: 'FileMode', subproject: str,
                  locale: T.Optional[str]):
         self.sources = sources
-        self.custom_install_dir = install_dir
-        self.custom_install_mode = install_mode
+        self.custom_install_dir = custom_install_dir
+        self.custom_install_mode = custom_install_mode
         self.subproject = subproject
         self.locale = locale
 
@@ -199,14 +199,14 @@ class EmptyDir(HoldableObject):
 
 class InstallDir(HoldableObject):
 
-    def __init__(self, src_subdir: str, inst_subdir: str, install_dir: str,
+    def __init__(self, source_subdir: str, installable_subdir: str, install_dir: str,
                  install_mode: 'FileMode',
                  exclude: T.Tuple[T.Set[str], T.Set[str]],
                  strip_directory: bool, subproject: str,
                  from_source_dir: bool = True,
                  install_tag: T.Optional[str] = None):
-        self.source_subdir = src_subdir
-        self.installable_subdir = inst_subdir
+        self.source_subdir = source_subdir
+        self.installable_subdir = installable_subdir
         self.install_dir = install_dir
         self.install_mode = install_mode
         self.exclude = exclude
@@ -367,9 +367,9 @@ class IncludeDirs(HoldableObject):
 
     """Internal representation of an include_directories call."""
 
-    def __init__(self, curdir: str, dirs: T.List[str], is_system: bool, extra_build_dirs: T.Optional[T.List[str]] = None):
+    def __init__(self, curdir: str, incdirs: T.List[str], is_system: bool, extra_build_dirs: T.Optional[T.List[str]] = None):
         self.curdir = curdir
-        self.incdirs = dirs
+        self.incdirs = incdirs
         self.is_system = is_system
 
         # Interpreter has validated that all given directories

mesonbuild/interpreterbase/decorators.py

@@ -569,10 +569,10 @@ class FeatureCheckBase(metaclass=abc.ABCMeta):
     feature_registry: T.ClassVar[T.Dict[str, T.Dict[str, T.Set[T.Tuple[str, T.Optional['mparser.BaseNode']]]]]]
     emit_notice = False
 
-    def __init__(self, feature_name: str, version: str, extra_message: T.Optional[str] = None, location: T.Optional['mparser.BaseNode'] = None):
+    def __init__(self, feature_name: str, feature_version: str, extra_message: str = '', location: T.Optional['mparser.BaseNode'] = None):
         self.feature_name = feature_name  # type: str
-        self.feature_version = version    # type: str
-        self.extra_message = extra_message or ''  # type: str
+        self.feature_version = feature_version    # type: str
+        self.extra_message = extra_message  # type: str
         self.location = location
 
     @staticmethod
@@ -656,7 +656,7 @@ class FeatureCheckBase(metaclass=abc.ABCMeta):
 
     @classmethod
     def single_use(cls, feature_name: str, version: str, subproject: str,
-                   extra_message: T.Optional[str] = None, location: T.Optional['mparser.BaseNode'] = None) -> None:
+                   extra_message: str = '', location: T.Optional['mparser.BaseNode'] = None) -> None:
         """Oneline version that instantiates and calls use()."""
         cls(feature_name, version, extra_message, location).use(subproject)