environment: make fully type safe

This as much as anything is to stop lying to envconfig about the
potential types it will be given.

mesonbuild/compilers/compilers.py

@@ -1424,6 +1424,8 @@ def get_global_options(lang: str,
 
     comp_options = env.options.get(comp_key, [])
     link_options = env.options.get(largkey, [])
+    assert isinstance(comp_options, (str, list)), 'for mypy'
+    assert isinstance(link_options, (str, list)), 'for mypy'
 
     cargs = options.UserStringArrayOption(
         argkey.name,

mesonbuild/envconfig.py

@@ -13,6 +13,9 @@
 from . import mlog
 from pathlib import Path
 
+if T.TYPE_CHECKING:
+    from .options import ElementaryOptionValues
+
 
 # These classes contains all the data pulled from configuration files (native
 # and cross file currently), and also assists with the reading environment
@@ -153,7 +156,7 @@ class CMakeSkipCompilerTest(Enum):
 class Properties:
     def __init__(
             self,
-            properties: T.Optional[T.Dict[str, T.Optional[T.Union[str, bool, int, T.List[str]]]]] = None,
+            properties: T.Optional[T.Dict[str, ElementaryOptionValues]] = None,
     ):
         self.properties = properties or {}
 
@@ -270,7 +273,13 @@ def __repr__(self) -> str:
         return f'<MachineInfo: {self.system} {self.cpu_family} ({self.cpu})>'
 
     @classmethod
-    def from_literal(cls, literal: T.Dict[str, str]) -> 'MachineInfo':
+    def from_literal(cls, raw: T.Dict[str, ElementaryOptionValues]) -> 'MachineInfo':
+        # We don't have enough type information to be sure of what we loaded
+        # So we need to accept that this might have ElementaryOptionValues, but
+        # then ensure that it's actually strings, since that's what the
+        # [*_machine] section should have.
+        assert all(isinstance(v, str) for v in raw.values()), 'for mypy'
+        literal = T.cast('T.Dict[str, str]', raw)
         minimum_literal = {'cpu', 'cpu_family', 'endian', 'system'}
         if set(literal) < minimum_literal:
             raise EnvironmentException(
@@ -389,7 +398,7 @@ class BinaryTable:
 
     def __init__(
             self,
-            binaries: T.Optional[T.Dict[str, T.Union[str, T.List[str]]]] = None,
+            binaries: T.Optional[T.Mapping[str, ElementaryOptionValues]] = None,
     ):
         self.binaries: T.Dict[str, T.List[str]] = {}
         if binaries:

mesonbuild/environment.py

@@ -41,10 +41,9 @@
 from mesonbuild import envconfig
 
 if T.TYPE_CHECKING:
-    from configparser import ConfigParser
-
     from .compilers import Compiler
     from .compilers.mixins.visualstudio import VisualStudioLikeCompiler
+    from .options import ElementaryOptionValues
     from .wrap.wrap import Resolver
     from . import cargo
 
@@ -633,7 +632,7 @@ def __init__(self, source_dir: str, build_dir: str, cmd_options: coredata.Shared
         #
         # Note that order matters because of 'buildtype', if it is after
         # 'optimization' and 'debug' keys, it override them.
-        self.options: T.MutableMapping[OptionKey, T.Union[str, T.List[str]]] = collections.OrderedDict()
+        self.options: T.MutableMapping[OptionKey, ElementaryOptionValues] = collections.OrderedDict()
 
         self.machinestore = machinefile.MachineFileStore(self.coredata.config_files, self.coredata.cross_files, self.source_dir)
 
@@ -701,7 +700,7 @@ def __init__(self, source_dir: str, build_dir: str, cmd_options: coredata.Shared
         # Store a global state of Cargo dependencies
         self.cargo: T.Optional[cargo.Interpreter] = None
 
-    def mfilestr2key(self, machine_file_string: str, section_subproject: str, machine: MachineChoice):
+    def mfilestr2key(self, machine_file_string: str, section_subproject: str, machine: MachineChoice) -> OptionKey:
         key = OptionKey.from_string(machine_file_string)
         assert key.machine == MachineChoice.HOST
         if key.subproject:
@@ -712,7 +711,8 @@ def mfilestr2key(self, machine_file_string: str, section_subproject: str, machin
             return key.evolve(machine=machine)
         return key
 
-    def _load_machine_file_options(self, config: 'ConfigParser', properties: Properties, machine: MachineChoice) -> None:
+    def _load_machine_file_options(self, config: T.Mapping[str, T.Mapping[str, ElementaryOptionValues]],
+                                   properties: Properties, machine: MachineChoice) -> None:
         """Read the contents of a Machine file and put it in the options store."""
 
         # Look for any options in the deprecated paths section, warn about

run_mypy.py

@@ -36,6 +36,7 @@
     # 'mesonbuild/coredata.py',
     'mesonbuild/depfile.py',
     'mesonbuild/envconfig.py',
+    'mesonbuild/environment.py',
     'mesonbuild/interpreter/compiler.py',
     'mesonbuild/interpreter/mesonmain.py',
     'mesonbuild/interpreter/interpreterobjects.py',