move OptionKey to mesonlib

There's starting to be a lot of things including coredata that coredata
needs to itself include. putting it in mesonlib makes more sense

19 files changed, 240 insertions, 238 deletions

diff --git a/mesonbuild/ast/introspection.py b/mesonbuild/ast/introspection.py
index 030ca8b..83b6843 100644
--- a/mesonbuild/ast/introspection.py
+++ b/mesonbuild/ast/introspection.py
@@ -19,7 +19,7 @@ from .interpreter import AstInterpreter
 from .visitor import AstVisitor
 from .. import compilers, environment, mesonlib, optinterpreter
 from .. import coredata as cdata
-from ..mesonlib import MachineChoice
+from ..mesonlib import MachineChoice, OptionKey
 from ..interpreterbase import InvalidArguments, TYPE_nvar
 from ..build import BuildTarget, Executable, Jar, SharedLibrary, SharedModule, StaticLibrary
 from ..mparser import BaseNode, ArithmeticNode, ArrayNode, ElementaryNode, IdNode, FunctionNode, StringNode
@@ -65,7 +65,7 @@ class IntrospectionInterpreter(AstInterpreter):
         self.coredata = self.environment.get_coredata()
         self.option_file = os.path.join(self.source_root, self.subdir, 'meson_options.txt')
         self.backend = backend
-        self.default_options = {cdata.OptionKey('backend'): self.backend}
+        self.default_options = {OptionKey('backend'): self.backend}
         self.project_data = {}    # type: T.Dict[str, T.Any]
         self.targets = []         # type: T.List[T.Dict[str, T.Any]]
         self.dependencies = []    # type: T.List[T.Dict[str, T.Any]]
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 39e0645..a4cdefd 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -43,11 +43,10 @@ from ..mesonlib import (
     File, LibType, MachineChoice, MesonException, OrderedSet, PerMachine,
     ProgressBar, quote_arg, unholder,
 )
-from ..mesonlib import get_compiler_for_source, has_path_sep
+from ..mesonlib import get_compiler_for_source, has_path_sep, OptionKey
 from .backends import CleanTrees
 from ..build import InvalidArguments
 from ..interpreter import Interpreter
-from ..coredata import OptionKey
 
 if T.TYPE_CHECKING:
     from ..linkers import StaticLinker
diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index f893e8f..8af83e6 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -28,10 +28,9 @@ from .. import mlog
 from .. import compilers
 from ..interpreter import Interpreter
 from ..mesonlib import (
-    MesonException, File, python_command, replace_if_different
+    MesonException, File, python_command, replace_if_different, OptionKey,
 )
 from ..environment import Environment, build_filename
-from ..coredata import OptionKey
 
 def autodetect_vs_version(build: T.Optional[build.Build], interpreter: T.Optional[Interpreter]):
     vs_version = os.getenv('VisualStudioVersion', None)
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 3b7e10d..d61ca73 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -28,7 +28,8 @@ from . import mlog
 from .mesonlib import (
     File, MesonException, MachineChoice, PerMachine, OrderedSet, listify,
     extract_as_list, typeslistify, stringlistify, classify_unity_sources,
-    get_filenames_templates_dict, substitute_values, has_path_sep, unholder
+    get_filenames_templates_dict, substitute_values, has_path_sep, unholder,
+    OptionKey,
 )
 from .compilers import (
     Compiler, all_languages, is_object, clink_langs, sort_clink, lang_suffixes,
@@ -36,7 +37,6 @@ from .compilers import (
 )
 from .linkers import StaticLinker
 from .interpreterbase import FeatureNew
-from .coredata import OptionKey
 
 if T.TYPE_CHECKING:
     from .coredata import KeyedOptionDictType, OptionDictType
diff --git a/mesonbuild/cmake/interpreter.py b/mesonbuild/cmake/interpreter.py
index 6125f15..5931fd1 100644
--- a/mesonbuild/cmake/interpreter.py
+++ b/mesonbuild/cmake/interpreter.py
@@ -22,7 +22,7 @@ from .executor import CMakeExecutor
 from .toolchain import CMakeToolchain, CMakeExecScope
 from .traceparser import CMakeTraceParser, CMakeGeneratorTarget
 from .. import mlog, mesonlib
-from ..mesonlib import MachineChoice, OrderedSet, version_compare, path_is_in_root, relative_to_if_possible
+from ..mesonlib import MachineChoice, OrderedSet, version_compare, path_is_in_root, relative_to_if_possible, OptionKey
 from ..mesondata import mesondata
 from ..compilers.compilers import lang_suffixes, header_suffixes, obj_suffixes, lib_suffixes, is_header
 from enum import Enum
@@ -31,7 +31,6 @@ from pathlib import Path
 import typing as T
 import re
 from os import environ
-from ..coredata import OptionKey
 
 from ..mparser import (
     Token,
diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index fe5f465..311e65a 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -16,7 +16,7 @@ import os.path
 import typing as T
 
 from .. import coredata
-from ..mesonlib import MachineChoice, MesonException, mlog, version_compare
+from ..mesonlib import MachineChoice, MesonException, mlog, version_compare, OptionKey
 from ..linkers import LinkerEnvVarsMixin
 from .c_function_attributes import C_FUNC_ATTRIBUTES
 from .mixins.clike import CLikeCompiler
@@ -37,7 +37,6 @@ from .compilers import (
     msvc_winlibs,
     Compiler,
 )
-from ..coredata import OptionKey
 
 if T.TYPE_CHECKING:
     from ..coredata import KeyedOptionDictType
diff --git a/mesonbuild/compilers/compilers.py b/mesonbuild/compilers/compilers.py
index acf3823..40bb9e6 100644
--- a/mesonbuild/compilers/compilers.py
+++ b/mesonbuild/compilers/compilers.py
@@ -25,14 +25,13 @@ from .. import mesonlib
 from ..linkers import LinkerEnvVarsMixin
 from ..mesonlib import (
     EnvironmentException, MachineChoice, MesonException,
-    Popen_safe, split_args, LibType, TemporaryDirectoryWinProof
+    Popen_safe, split_args, LibType, TemporaryDirectoryWinProof, OptionKey,
 )
 from ..envconfig import (
     get_env_var
 )
 
 from ..arglist import CompilerArgs
-from ..coredata import OptionKey
 
 if T.TYPE_CHECKING:
     from ..build import BuildTarget
diff --git a/mesonbuild/compilers/cpp.py b/mesonbuild/compilers/cpp.py
index 578e362..b94beb6 100644
--- a/mesonbuild/compilers/cpp.py
+++ b/mesonbuild/compilers/cpp.py
@@ -19,7 +19,7 @@ import typing as T
 
 from .. import coredata
 from .. import mlog
-from ..mesonlib import MesonException, MachineChoice, version_compare
+from ..mesonlib import MesonException, MachineChoice, version_compare, OptionKey
 
 from ..linkers import LinkerEnvVarsMixin
 from .compilers import (
@@ -41,8 +41,6 @@ from .mixins.elbrus import ElbrusCompiler
 from .mixins.pgi import PGICompiler
 from .mixins.emscripten import EmscriptenMixin
 
-from ..coredata import OptionKey
-
 if T.TYPE_CHECKING:
     from ..coredata import KeyedOptionDictType
     from ..dependencies import Dependency, ExternalProgram
diff --git a/mesonbuild/compilers/cuda.py b/mesonbuild/compilers/cuda.py
index da1e002..7fa3e4f 100644
--- a/mesonbuild/compilers/cuda.py
+++ b/mesonbuild/compilers/cuda.py
@@ -17,9 +17,11 @@ import os.path
 import typing as T
 
 from .. import coredata
-from ..coredata import OptionKey
 from .. import mlog
-from ..mesonlib import EnvironmentException, MachineChoice, Popen_safe, OptionOverrideProxy, is_windows, LibType
+from ..mesonlib import (
+    EnvironmentException, MachineChoice, Popen_safe, OptionOverrideProxy,
+    is_windows, LibType, OptionKey,
+)
 from .compilers import (Compiler, cuda_buildtype_args, cuda_optimization_args,
                         cuda_debug_args)
 
diff --git a/mesonbuild/compilers/fortran.py b/mesonbuild/compilers/fortran.py
index edd7911..d65d585 100644
--- a/mesonbuild/compilers/fortran.py
+++ b/mesonbuild/compilers/fortran.py
@@ -17,7 +17,6 @@ import typing as T
 import subprocess, os
 
 from .. import coredata
-from ..coredata import OptionKey
 from .compilers import (
     clike_debug_args,
     Compiler,
@@ -32,7 +31,8 @@ from .mixins.elbrus import ElbrusCompiler
 from .mixins.pgi import PGICompiler
 
 from mesonbuild.mesonlib import (
-    version_compare, EnvironmentException, MesonException, MachineChoice, LibType
+    version_compare, EnvironmentException, MesonException, MachineChoice,
+    LibType, OptionKey,
 )
 
 if T.TYPE_CHECKING:
diff --git a/mesonbuild/compilers/mixins/emscripten.py b/mesonbuild/compilers/mixins/emscripten.py
index aacea15..b480de3 100644
--- a/mesonbuild/compilers/mixins/emscripten.py
+++ b/mesonbuild/compilers/mixins/emscripten.py
@@ -18,6 +18,7 @@ import os.path
 import typing as T
 
 from ... import coredata
+from ...mesonlib import OptionKey
 
 if T.TYPE_CHECKING:
     from ...environment import Environment
@@ -50,14 +51,14 @@ class EmscriptenMixin(Compiler):
 
     def thread_link_flags(self, env: 'Environment') -> T.List[str]:
         args = ['-s', 'USE_PTHREADS=1']
-        count: int = env.coredata.compiler_options[coredata.OptionKey('thread_count', lang=self.language, machine=self.for_machine)].value  # type: ignore
+        count: int = env.coredata.compiler_options[OptionKey('thread_count', lang=self.language, machine=self.for_machine)].value  # type: ignore
         if count:
             args.extend(['-s', 'PTHREAD_POOL_SIZE={}'.format(count)])
         return args
 
     def get_options(self) -> 'coredata.KeyedOptionDictType':
         opts = super().get_options()
-        key = coredata.OptionKey('thread_count', machine=self.for_machine, lang=self.language)
+        key = OptionKey('thread_count', machine=self.for_machine, lang=self.language)
         opts.update({
             key: coredata.UserIntegerOption(
                 'Number of threads to use in web assembly, set to 0 to disable',
diff --git a/mesonbuild/compilers/rust.py b/mesonbuild/compilers/rust.py
index cf1af0a..8a1acc7 100644
--- a/mesonbuild/compilers/rust.py
+++ b/mesonbuild/compilers/rust.py
@@ -17,8 +17,10 @@ import textwrap
 import typing as T
 
 from .. import coredata
-from ..coredata import OptionKey
-from ..mesonlib import EnvironmentException, MachineChoice, MesonException, Popen_safe
+from ..mesonlib import (
+    EnvironmentException, MachineChoice, MesonException, Popen_safe,
+    OptionKey,
+)
 from .compilers import Compiler, rust_buildtype_args, clike_debug_args
 
 if T.TYPE_CHECKING:
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 97f5fff..f09c398 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -20,7 +20,8 @@ from pathlib import PurePath
 from collections import OrderedDict, defaultdict
 from .mesonlib import (
     MesonException, EnvironmentException, MachineChoice, PerMachine,
-    default_libdir, default_libexecdir, default_prefix, split_args
+    default_libdir, default_libexecdir, default_prefix, split_args,
+    OptionKey,
 )
 from .wrap import WrapMode
 import ast
@@ -49,201 +50,6 @@ default_yielding = False
 _T = T.TypeVar('_T')
 
 
-class OptionType(enum.Enum):
-
-    """Enum used to specify what kind of argument a thing is."""
-
-    BUILTIN = 0
-    BASE = 1
-    COMPILER = 2
-    PROJECT = 3
-    BACKEND = 4
-
-
-def classify_argument(key: 'OptionKey') -> OptionType:
-    """Classify arguments into groups so we know which dict to assign them to."""
-
-    from .compilers import base_options
-    all_builtins = set(BUILTIN_OPTIONS) | set(BUILTIN_OPTIONS_PER_MACHINE) | set(builtin_dir_noprefix_options)
-
-    if key.name in base_options:
-        assert key.machine is MachineChoice.HOST, str(key)
-        return OptionType.BASE
-    elif key.lang is not None:
-        return OptionType.COMPILER
-    elif key.name in all_builtins:
-        return OptionType.BUILTIN
-    elif key.name.startswith('backend_'):
-        assert key.machine is MachineChoice.HOST, str(key)
-        return OptionType.BACKEND
-    else:
-        assert key.machine is MachineChoice.HOST, str(key)
-        return OptionType.PROJECT
-
-
-class OptionKey:
-
-    """Represents an option key in the various option dictionaries.
-
-    This provides a flexible, powerful way to map option names from their
-    external form (things like subproject:build.option) to something that
-    internally easier to reason about and produce.
-    """
-
-    __slots__ = ['name', 'subproject', 'machine', 'lang', '_hash', 'type']
-
-    name: str
-    subproject: str
-    machine: MachineChoice
-    lang: T.Optional[str]
-    _hash: int
-    type: OptionType
-
-    def __init__(self, name: str, subproject: str = '',
-                 machine: MachineChoice = MachineChoice.HOST,
-                 lang: T.Optional[str] = None, _type: T.Optional[OptionType] = None):
-        # the _type option to the constructor is kinda private. We want to be
-        # able tos ave the state and avoid the lookup function when
-        # pickling/unpickling, but we need to be able to calculate it when
-        # constructing a new OptionKey
-        object.__setattr__(self, 'name', name)
-        object.__setattr__(self, 'subproject', subproject)
-        object.__setattr__(self, 'machine', machine)
-        object.__setattr__(self, 'lang', lang)
-        object.__setattr__(self, '_hash', hash((name, subproject, machine, lang)))
-        if _type is None:
-            _type = classify_argument(self)
-        object.__setattr__(self, 'type', _type)
-
-    def __setattr__(self, key: str, value: T.Any) -> None:
-        raise AttributeError('OptionKey instances do not support mutation.')
-
-    def __getstate__(self) -> T.Dict[str, T.Any]:
-        return {
-            'name': self.name,
-            'subproject': self.subproject,
-            'machine': self.machine,
-            'lang': self.lang,
-            '_type': self.type,
-        }
-
-    def __setstate__(self, state: T.Dict[str, T.Any]) -> None:
-        """De-serialize the state of a pickle.
-
-        This is very clever. __init__ is not a constructor, it's an
-        initializer, therefore it's safe to call more than once. We create a
-        state in the custom __getstate__ method, which is valid to pass
-        unsplatted to the initializer.
-        """
-        self.__init__(**state)
-
-    def __hash__(self) -> int:
-        return self._hash
-
-    def __eq__(self, other: object) -> bool:
-        if isinstance(other, OptionKey):
-            return (
-                self.name == other.name and
-                self.subproject == other.subproject and
-                self.machine is other.machine and
-                self.lang == other.lang)
-        return NotImplemented
-
-    def __str__(self) -> str:
-        out = self.name
-        if self.lang:
-            out = f'{self.lang}_{out}'
-        if self.machine is MachineChoice.BUILD:
-            out = f'build.{out}'
-        if self.subproject:
-            out = f'{self.subproject}:{out}'
-        return out
-
-    def __repr__(self) -> str:
-        return f'OptionKey({repr(self.name)}, {repr(self.subproject)}, {repr(self.machine)}, {repr(self.lang)})'
-
-    @classmethod
-    def from_string(cls, raw: str) -> 'OptionKey':
-        """Parse the raw command line format into a three part tuple.
-
-        This takes strings like `mysubproject:build.myoption` and Creates an
-        OptionKey out of them.
-        """
-
-        try:
-            subproject, raw2 = raw.split(':')
-        except ValueError:
-            subproject, raw2 = '', raw
-
-        if raw2.startswith('build.'):
-            raw3 = raw2.lstrip('build.')
-            for_machine = MachineChoice.BUILD
-        else:
-            raw3 = raw2
-            for_machine = MachineChoice.HOST
-
-        from .compilers import all_languages
-        if any(raw3.startswith(f'{l}_') for l in all_languages):
-            lang, opt = raw3.split('_', 1)
-        else:
-            lang, opt = None, raw3
-        assert ':' not in opt
-        assert 'build.' not in opt
-
-        return cls(opt, subproject, for_machine, lang)
-
-    def evolve(self, name: T.Optional[str] = None, subproject: T.Optional[str] = None,
-               machine: T.Optional[MachineChoice] = None, lang: T.Optional[str] = '') -> 'OptionKey':
-        """Create a new copy of this key, but with alterted members.
-
-        For example:
-        >>> a = OptionKey('foo', '', MachineChoice.Host)
-        >>> b = OptionKey('foo', 'bar', MachineChoice.Host)
-        >>> b == a.evolve(subproject='bar')
-        True
-        """
-        # We have to be a little clever with lang here, because lang is valid
-        # as None, for non-compiler options
-        return OptionKey(
-            name if name is not None else self.name,
-            subproject if subproject is not None else self.subproject,
-            machine if machine is not None else self.machine,
-            lang if lang != '' else self.lang,
-        )
-
-    def as_root(self) -> 'OptionKey':
-        """Convenience method for key.evolve(subproject='')."""
-        return self.evolve(subproject='')
-
-    def as_build(self) -> 'OptionKey':
-        """Convenience method for key.evolve(machine=MachinceChoice.BUILD)."""
-        return self.evolve(machine=MachineChoice.BUILD)
-
-    def as_host(self) -> 'OptionKey':
-        """Convenience method for key.evolve(machine=MachinceChoice.HOST)."""
-        return self.evolve(machine=MachineChoice.HOST)
-
-    def is_backend(self) -> bool:
-        """Convenience method to check if this is a backend option."""
-        return self.type is OptionType.BACKEND
-
-    def is_builtin(self) -> bool:
-        """Convenience method to check if this is a builtin option."""
-        return self.type is OptionType.BUILTIN
-
-    def is_compiler(self) -> bool:
-        """Convenience method to check if this is a builtin option."""
-        return self.type is OptionType.COMPILER
-
-    def is_project(self) -> bool:
-        """Convenience method to check if this is a project option."""
-        return self.type is OptionType.PROJECT
-
-    def is_base(self) -> bool:
-        """Convenience method to check if this is a base option."""
-        return self.type is OptionType.BASE
-
-
 class MesonVersionMismatchException(MesonException):
     '''Build directory generated with Meson version is incompatible with current version'''
     def __init__(self, old_version: str, current_version: str) -> None:
diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index 3120279..3ea078a 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -23,7 +23,7 @@ from .linkers import ArLinker, ArmarLinker, VisualStudioLinker, DLinker, CcrxLin
 from . import mesonlib
 from .mesonlib import (
     MesonException, EnvironmentException, MachineChoice, Popen_safe,
-    PerMachineDefaultable, PerThreeMachineDefaultable, split_args, quote_arg
+    PerMachineDefaultable, PerThreeMachineDefaultable, split_args, quote_arg, OptionKey
 )
 from . import mlog
 
@@ -605,7 +605,7 @@ class Environment:
         #
         # Note that order matters because of 'buildtype', if it is after
         # 'optimization' and 'debug' keys, it override them.
-        self.options: T.MutableMapping[coredata.OptionKey, str] = collections.OrderedDict()
+        self.options: T.MutableMapping[OptionKey, str] = collections.OrderedDict()
 
         ## Read in native file(s) to override build machine configuration
 
@@ -655,9 +655,9 @@ class Environment:
 
         # Warn if the user is using two different ways of setting build-type
         # options that override each other
-        bt = coredata.OptionKey('buildtype')
-        db = coredata.OptionKey('debug')
-        op = coredata.OptionKey('optimization')
+        bt = OptionKey('buildtype')
+        db = OptionKey('debug')
+        op = OptionKey('optimization')
         if bt in self.options and (db in self.options or op in self.options):
             mlog.warning('Recommend using either -Dbuildtype or -Doptimization + -Ddebug. '
                          'Using both is redundant since they override each other. '
@@ -723,7 +723,7 @@ class Environment:
         if paths:
             mlog.deprecation('The [paths] section is deprecated, use the [built-in options] section instead.')
             for k, v in paths.items():
-                self.options[coredata.OptionKey.from_string(k).evolve(machine=machine)] = v
+                self.options[OptionKey.from_string(k).evolve(machine=machine)] = v
         deprecated_properties = set()
         for lang in compilers.all_languages:
             deprecated_properties.add(lang + '_args')
@@ -731,7 +731,7 @@ class Environment:
         for k, v in properties.properties.copy().items():
             if k in deprecated_properties:
                 mlog.deprecation('{} in the [properties] section of the machine file is deprecated, use the [built-in options] section.'.format(k))
-                self.options[coredata.OptionKey.from_string(k).evolve(machine=machine)] = v
+                self.options[OptionKey.from_string(k).evolve(machine=machine)] = v
                 del properties.properties[k]
         for section, values in config.items():
             if ':' in section:
@@ -740,12 +740,12 @@ class Environment:
                 subproject = ''
             if section == 'built-in options':
                 for k, v in values.items():
-                    key = coredata.OptionKey.from_string(k).evolve(subproject=subproject, machine=machine)
+                    key = OptionKey.from_string(k).evolve(subproject=subproject, machine=machine)
                     self.options[key] = v
             elif section == 'project options':
                 for k, v in values.items():
                     # Project options are always for the machine machine
-                    key = coredata.OptionKey.from_string(k).evolve(subproject=subproject)
+                    key = OptionKey.from_string(k).evolve(subproject=subproject)
                     self.options[key] = v
 
     def set_default_options_from_env(self) -> None:
@@ -763,7 +763,7 @@ class Environment:
                     # FIXME: We should remember if we took the value from env to warn
                     # if it changes on future invocations.
                     if self.first_invocation:
-                        key = coredata.OptionKey(keyname, machine=for_machine)
+                        key = OptionKey(keyname, machine=for_machine)
                         self.options.setdefault(key, p_list)
 
     def create_new_coredata(self, options: 'argparse.Namespace') -> None:
@@ -938,7 +938,7 @@ class Environment:
         elif isinstance(comp_class.LINKER_PREFIX, list):
             check_args = comp_class.LINKER_PREFIX + ['/logo'] + comp_class.LINKER_PREFIX + ['--version']
 
-        check_args += self.coredata.compiler_options[coredata.OptionKey('args', lang=comp_class.language, machine=for_machine)].value
+        check_args += self.coredata.compiler_options[OptionKey('args', lang=comp_class.language, machine=for_machine)].value
 
         override = []  # type: T.List[str]
         value = self.lookup_binary_entry(for_machine, comp_class.language + '_ld')
@@ -1004,7 +1004,7 @@ class Environment:
         """
         self.coredata.add_lang_args(comp_class.language, comp_class, for_machine, self)
         extra_args = extra_args or []
-        extra_args += self.coredata.compiler_options[coredata.OptionKey('args', lang=comp_class.language, machine=for_machine)].value
+        extra_args += self.coredata.compiler_options[OptionKey('args', lang=comp_class.language, machine=for_machine)].value
 
         if isinstance(comp_class.LINKER_PREFIX, str):
             check_args = [comp_class.LINKER_PREFIX + '--version'] + extra_args
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 6aba3e7..b4336eb 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -3067,7 +3067,7 @@ external dependencies (including libraries) must go to "dependencies".''')
             if v is not None:
                 return v
 
-        key = coredata.OptionKey.from_string(optname)
+        key = mesonlib.OptionKey.from_string(optname)
         for opts in [self.coredata.compiler_options]:
             v = opts.get(key)
             if v is None or v.yielding:
diff --git a/mesonbuild/mconf.py b/mesonbuild/mconf.py
index c14d701..70d6806 100644
--- a/mesonbuild/mconf.py
+++ b/mesonbuild/mconf.py
@@ -21,7 +21,8 @@ from .mesonlib import MachineChoice
 
 if T.TYPE_CHECKING:
     import argparse
-    from .coredata import OptionKey, UserOption
+    from .coredata import UserOption
+    from .mesonlib import OptionKey
 
 def add_arguments(parser: 'argparse.ArgumentParser') -> None:
     coredata.register_builtin_arguments(parser)
diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index 805e679..8252f79 100644
--- a/mesonbuild/mesonlib.py
+++ b/mesonbuild/mesonlib.py
@@ -14,6 +14,7 @@
 
 """A library of random helper functionality."""
 from pathlib import Path
+import enum
 import sys
 import stat
 import time
@@ -1780,3 +1781,199 @@ class OptionOverrideProxy(collections.abc.MutableMapping):
 
     def copy(self) -> 'OptionOverrideProxy':
         return OptionOverrideProxy(self.overrides.copy(), self.options.copy())
+
+
+class OptionType(enum.Enum):
+
+    """Enum used to specify what kind of argument a thing is."""
+
+    BUILTIN = 0
+    BASE = 1
+    COMPILER = 2
+    PROJECT = 3
+    BACKEND = 4
+
+
+def _classify_argument(key: 'OptionKey') -> OptionType:
+    """Classify arguments into groups so we know which dict to assign them to."""
+
+    from .compilers import base_options
+    from .coredata import BUILTIN_OPTIONS, BUILTIN_OPTIONS_PER_MACHINE, builtin_dir_noprefix_options
+    all_builtins = set(BUILTIN_OPTIONS) | set(BUILTIN_OPTIONS_PER_MACHINE) | set(builtin_dir_noprefix_options)
+
+    if key.name in base_options:
+        assert key.machine is MachineChoice.HOST, str(key)
+        return OptionType.BASE
+    elif key.lang is not None:
+        return OptionType.COMPILER
+    elif key.name in all_builtins:
+        return OptionType.BUILTIN
+    elif key.name.startswith('backend_'):
+        assert key.machine is MachineChoice.HOST, str(key)
+        return OptionType.BACKEND
+    else:
+        assert key.machine is MachineChoice.HOST, str(key)
+        return OptionType.PROJECT
+
+
+class OptionKey:
+
+    """Represents an option key in the various option dictionaries.
+
+    This provides a flexible, powerful way to map option names from their
+    external form (things like subproject:build.option) to something that
+    internally easier to reason about and produce.
+    """
+
+    __slots__ = ['name', 'subproject', 'machine', 'lang', '_hash', 'type']
+
+    name: str
+    subproject: str
+    machine: MachineChoice
+    lang: T.Optional[str]
+    _hash: int
+    type: OptionType
+
+    def __init__(self, name: str, subproject: str = '',
+                 machine: MachineChoice = MachineChoice.HOST,
+                 lang: T.Optional[str] = None, _type: T.Optional[OptionType] = None):
+        # the _type option to the constructor is kinda private. We want to be
+        # able tos ave the state and avoid the lookup function when
+        # pickling/unpickling, but we need to be able to calculate it when
+        # constructing a new OptionKey
+        object.__setattr__(self, 'name', name)
+        object.__setattr__(self, 'subproject', subproject)
+        object.__setattr__(self, 'machine', machine)
+        object.__setattr__(self, 'lang', lang)
+        object.__setattr__(self, '_hash', hash((name, subproject, machine, lang)))
+        if _type is None:
+            _type = _classify_argument(self)
+        object.__setattr__(self, 'type', _type)
+
+    def __setattr__(self, key: str, value: T.Any) -> None:
+        raise AttributeError('OptionKey instances do not support mutation.')
+
+    def __getstate__(self) -> T.Dict[str, T.Any]:
+        return {
+            'name': self.name,
+            'subproject': self.subproject,
+            'machine': self.machine,
+            'lang': self.lang,
+            '_type': self.type,
+        }
+
+    def __setstate__(self, state: T.Dict[str, T.Any]) -> None:
+        """De-serialize the state of a pickle.
+
+        This is very clever. __init__ is not a constructor, it's an
+        initializer, therefore it's safe to call more than once. We create a
+        state in the custom __getstate__ method, which is valid to pass
+        unsplatted to the initializer.
+        """
+        self.__init__(**state)
+
+    def __hash__(self) -> int:
+        return self._hash
+
+    def __eq__(self, other: object) -> bool:
+        if isinstance(other, OptionKey):
+            return (
+                self.name == other.name and
+                self.subproject == other.subproject and
+                self.machine is other.machine and
+                self.lang == other.lang)
+        return NotImplemented
+
+    def __str__(self) -> str:
+        out = self.name
+        if self.lang:
+            out = f'{self.lang}_{out}'
+        if self.machine is MachineChoice.BUILD:
+            out = f'build.{out}'
+        if self.subproject:
+            out = f'{self.subproject}:{out}'
+        return out
+
+    def __repr__(self) -> str:
+        return f'OptionKey({repr(self.name)}, {repr(self.subproject)}, {repr(self.machine)}, {repr(self.lang)})'
+
+    @classmethod
+    def from_string(cls, raw: str) -> 'OptionKey':
+        """Parse the raw command line format into a three part tuple.
+
+        This takes strings like `mysubproject:build.myoption` and Creates an
+        OptionKey out of them.
+        """
+
+        try:
+            subproject, raw2 = raw.split(':')
+        except ValueError:
+            subproject, raw2 = '', raw
+
+        if raw2.startswith('build.'):
+            raw3 = raw2.lstrip('build.')
+            for_machine = MachineChoice.BUILD
+        else:
+            raw3 = raw2
+            for_machine = MachineChoice.HOST
+
+        from .compilers import all_languages
+        if any(raw3.startswith(f'{l}_') for l in all_languages):
+            lang, opt = raw3.split('_', 1)
+        else:
+            lang, opt = None, raw3
+        assert ':' not in opt
+        assert 'build.' not in opt
+
+        return cls(opt, subproject, for_machine, lang)
+
+    def evolve(self, name: T.Optional[str] = None, subproject: T.Optional[str] = None,
+               machine: T.Optional[MachineChoice] = None, lang: T.Optional[str] = '') -> 'OptionKey':
+        """Create a new copy of this key, but with alterted members.
+
+        For example:
+        >>> a = OptionKey('foo', '', MachineChoice.Host)
+        >>> b = OptionKey('foo', 'bar', MachineChoice.Host)
+        >>> b == a.evolve(subproject='bar')
+        True
+        """
+        # We have to be a little clever with lang here, because lang is valid
+        # as None, for non-compiler options
+        return OptionKey(
+            name if name is not None else self.name,
+            subproject if subproject is not None else self.subproject,
+            machine if machine is not None else self.machine,
+            lang if lang != '' else self.lang,
+        )
+
+    def as_root(self) -> 'OptionKey':
+        """Convenience method for key.evolve(subproject='')."""
+        return self.evolve(subproject='')
+
+    def as_build(self) -> 'OptionKey':
+        """Convenience method for key.evolve(machine=MachinceChoice.BUILD)."""
+        return self.evolve(machine=MachineChoice.BUILD)
+
+    def as_host(self) -> 'OptionKey':
+        """Convenience method for key.evolve(machine=MachinceChoice.HOST)."""
+        return self.evolve(machine=MachineChoice.HOST)
+
+    def is_backend(self) -> bool:
+        """Convenience method to check if this is a backend option."""
+        return self.type is OptionType.BACKEND
+
+    def is_builtin(self) -> bool:
+        """Convenience method to check if this is a builtin option."""
+        return self.type is OptionType.BUILTIN
+
+    def is_compiler(self) -> bool:
+        """Convenience method to check if this is a builtin option."""
+        return self.type is OptionType.COMPILER
+
+    def is_project(self) -> bool:
+        """Convenience method to check if this is a project option."""
+        return self.type is OptionType.PROJECT
+
+    def is_base(self) -> bool:
+        """Convenience method to check if this is a base option."""
+        return self.type is OptionType.BASE
\ No newline at end of file
diff --git a/run_tests.py b/run_tests.py
index 15e643a..ec58ac0 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -34,7 +34,8 @@ from mesonbuild import mesonmain
 from mesonbuild import mtest
 from mesonbuild import mlog
 from mesonbuild.environment import Environment, detect_ninja
-from mesonbuild.coredata import backendlist, version as meson_version, OptionKey
+from mesonbuild.coredata import backendlist, version as meson_version
+from mesonbuild.mesonlib import OptionKey
 
 NINJA_1_9_OR_NEWER = False
 NINJA_CMD = None
diff --git a/run_unittests.py b/run_unittests.py
index 0236909..744556e 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -59,12 +59,11 @@ from mesonbuild.mesonlib import (
     quote_arg, relpath, is_linux, git, GIT
 )
 from mesonbuild.environment import detect_ninja
-from mesonbuild.mesonlib import MesonException, EnvironmentException
+from mesonbuild.mesonlib import MesonException, EnvironmentException, OptionKey
 from mesonbuild.dependencies import PkgConfigDependency, ExternalProgram
 import mesonbuild.dependencies.base
 from mesonbuild.build import Target, ConfigurationData
 import mesonbuild.modules.pkgconfig
-from mesonbuild.coredata import OptionKey
 
 from mesonbuild.mtest import TAPParser, TestResult