PkgConfigDependency: Move CLI handling into its own abstraction

This makes the code cleaner and will allow to have other implementations
in the future.

9 files changed, 254 insertions, 199 deletions

diff --git a/mesonbuild/dependencies/hdf5.py b/mesonbuild/dependencies/hdf5.py
index 84f2812..501e89d 100644
--- a/mesonbuild/dependencies/hdf5.py
+++ b/mesonbuild/dependencies/hdf5.py
@@ -18,15 +18,13 @@ from __future__ import annotations
 import functools
 import os
 import re
-import subprocess
 from pathlib import Path
 
-from ..mesonlib import Popen_safe, OrderedSet, join_args
-from ..programs import ExternalProgram
+from ..mesonlib import OrderedSet, join_args
 from .base import DependencyException, DependencyMethods
 from .configtool import ConfigToolDependency
 from .detect import packages
-from .pkgconfig import PkgConfigDependency
+from .pkgconfig import PkgConfigDependency, PkgConfigInterface
 from .factory import factory_methods
 import typing as T
 
@@ -157,19 +155,14 @@ def hdf5_factory(env: 'Environment', for_machine: 'MachineChoice',
     if DependencyMethods.PKGCONFIG in methods:
         # Use an ordered set so that these remain the first tried pkg-config files
         pkgconfig_files = OrderedSet(['hdf5', 'hdf5-serial'])
-        PCEXE = PkgConfigDependency._detect_pkgbin(False, env, for_machine)
-        pcenv = PkgConfigDependency.setup_env(os.environ, env, for_machine)
-        if PCEXE:
-            assert isinstance(PCEXE, ExternalProgram)
+        pkg = PkgConfigInterface.instance(env, for_machine, silent=False)
+        if pkg:
             # some distros put hdf5-1.2.3.pc with version number in .pc filename.
-            ret, stdout, _ = Popen_safe(PCEXE.get_command() + ['--list-all'], stderr=subprocess.DEVNULL, env=pcenv)
-            if ret.returncode == 0:
-                for pkg in stdout.split('\n'):
-                    if pkg.startswith('hdf5'):
-                        pkgconfig_files.add(pkg.split(' ', 1)[0])
-
-        for pkg in pkgconfig_files:
-            candidates.append(functools.partial(HDF5PkgConfigDependency, pkg, env, kwargs, language))
+            for mod in pkg.list_all():
+                if mod.startswith('hdf5'):
+                    pkgconfig_files.add(mod)
+        for mod in pkgconfig_files:
+            candidates.append(functools.partial(HDF5PkgConfigDependency, mod, env, kwargs, language))
 
     if DependencyMethods.CONFIG_TOOL in methods:
         candidates.append(functools.partial(HDF5ConfigToolDependency, 'hdf5', env, kwargs, language))
diff --git a/mesonbuild/dependencies/pkgconfig.py b/mesonbuild/dependencies/pkgconfig.py
index 37f2ecb..cfe9cbb 100644
--- a/mesonbuild/dependencies/pkgconfig.py
+++ b/mesonbuild/dependencies/pkgconfig.py
@@ -31,64 +31,142 @@ if T.TYPE_CHECKING:
     from ..utils.core import EnvironOrDict
     from .._typing import ImmutableListProtocol
 
-class PkgConfigDependency(ExternalDependency):
+class PkgConfigInterface:
+    '''Base class wrapping a pkg-config implementation'''
+
+    @staticmethod
+    def instance(env: Environment, for_machine: MachineChoice, silent: bool) -> T.Optional[PkgConfigInterface]:
+        impl = PkgConfigCLI(env, for_machine, silent)
+        if not impl.found():
+            return None
+        return impl
+
+    def found(self) -> bool:
+        '''Return whether pkg-config is supported'''
+        raise NotImplementedError
+
+    def version(self, name: str) -> T.Optional[str]:
+        '''Return module version or None if not found'''
+        raise NotImplementedError
+
+    def cflags(self, name: str, allow_system: bool = False,
+               define_variable: T.Optional[ImmutableListProtocol[str]] = None) -> T.List[str]:
+        '''Return module cflags
+           @allow_system: If False, remove default system include paths
+        '''
+        raise NotImplementedError
+
+    def libs(self, name: str, static: bool = False, allow_system: bool = False,
+             define_variable: T.Optional[ImmutableListProtocol[str]] = None) -> T.List[str]:
+        '''Return module libs
+           @static: If True, also include private libraries
+           @allow_system: If False, remove default system libraries search paths
+        '''
+        raise NotImplementedError
+
+    def variable(self, name: str, variable_name: str,
+                 define_variable: ImmutableListProtocol[str]) -> T.Optional[str]:
+        '''Return module variable or None if variable is not defined'''
+        raise NotImplementedError
+
+    def list_all(self) -> T.List[str]:
+        '''Return all available pkg-config modules'''
+        raise NotImplementedError
+
+class PkgConfigCLI(PkgConfigInterface):
+    '''pkg-config CLI implementation'''
+
     # The class's copy of the pkg-config path. Avoids having to search for it
     # multiple times in the same Meson invocation.
-    class_pkgbin: PerMachine[T.Union[None, bool, ExternalProgram]] = PerMachine(None, None)
+    class_pkgbin: PerMachine[T.Union[None, T.Literal[False], ExternalProgram]] = PerMachine(None, None)
     # We cache all pkg-config subprocess invocations to avoid redundant calls
     pkgbin_cache: T.Dict[
         T.Tuple[ExternalProgram, T.Tuple[str, ...], T.FrozenSet[T.Tuple[str, str]]],
         T.Tuple[int, str, str]
     ] = {}
 
-    def __init__(self, name: str, environment: 'Environment', kwargs: T.Dict[str, T.Any], language: T.Optional[str] = None) -> None:
-        super().__init__(DependencyTypeName('pkgconfig'), environment, kwargs, language=language)
-        self.name = name
-        self.is_libtool = False
+    def __init__(self, env: Environment, for_machine: MachineChoice, silent: bool) -> None:
+        self.env = env
+        self.for_machine = for_machine
         # Store a copy of the pkg-config path on the object itself so it is
         # stored in the pickled coredata and recovered.
-        self.pkgbin = self._detect_pkgbin(self.silent, self.env, self.for_machine)
-        if self.pkgbin is False:
-            self.pkgbin = None
-            msg = f'Pkg-config binary for machine {self.for_machine} not found. Giving up.'
-            if self.required:
-                raise DependencyException(msg)
-            else:
-                mlog.debug(msg)
-                return
+        self.pkgbin = self._detect_pkgbin(env, for_machine, silent)
 
-        assert isinstance(self.pkgbin, ExternalProgram)
-        mlog.debug('Determining dependency {!r} with pkg-config executable '
-                   '{!r}'.format(name, self.pkgbin.get_path()))
-        ret, self.version, _ = self._call_pkgbin(['--modversion', name])
+    def found(self) -> bool:
+        return bool(self.pkgbin)
+
+    def version(self, name: str) -> T.Optional[str]:
+        mlog.debug(f'Determining dependency {name!r} with pkg-config executable {self.pkgbin.get_path()!r}')
+        ret, version, _ = self._call_pkgbin(['--modversion', name])
+        return version if ret == 0 else None
+
+    @staticmethod
+    def _define_variable_args(define_variable: T.Optional[ImmutableListProtocol[str]]) -> T.List[str]:
+        if define_variable:
+            return ['--define-variable=' + '='.join(define_variable)]
+        return []
+
+    def cflags(self, name: str, allow_system: bool = False,
+               define_variable: T.Optional[ImmutableListProtocol[str]] = None) -> T.List[str]:
+        env = None
+        if allow_system:
+            env = os.environ.copy()
+            env['PKG_CONFIG_ALLOW_SYSTEM_CFLAGS'] = '1'
+        args: T.List[str] = []
+        args += self._define_variable_args(define_variable)
+        args += ['--cflags', name]
+        ret, out, err = self._call_pkgbin(args, env=env)
         if ret != 0:
-            return
+            raise DependencyException(f'Could not generate cflags for {name}:\n{err}\n')
+        return self._split_args(out)
 
-        self.is_found = True
+    def libs(self, name: str, static: bool = False, allow_system: bool = False,
+             define_variable: T.Optional[ImmutableListProtocol[str]] = None) -> T.List[str]:
+        env = None
+        if allow_system:
+            env = os.environ.copy()
+            env['PKG_CONFIG_ALLOW_SYSTEM_LIBS'] = '1'
+        args: T.List[str] = []
+        args += self._define_variable_args(define_variable)
+        if static:
+            args.append('--static')
+        args += ['--libs', name]
+        ret, out, err = self._call_pkgbin(args, env=env)
+        if ret != 0:
+            raise DependencyException(f'Could not generate libs for {name}:\n{err}\n')
+        return self._split_args(out)
+
+    def variable(self, name: str, variable_name: str,
+                 define_variable: ImmutableListProtocol[str]) -> T.Optional[str]:
+        args: T.List[str] = []
+        args += self._define_variable_args(define_variable)
+        args += ['--variable=' + variable_name, name]
+        ret, out, err = self._call_pkgbin(args)
+        if ret != 0:
+            raise DependencyException(f'Could not get variable for {name}:\n{err}\n')
+        variable = out.strip()
+        # pkg-config doesn't distinguish between empty and nonexistent variables
+        # use the variable list to check for variable existence
+        if not variable:
+            ret, out, _ = self._call_pkgbin(['--print-variables', name])
+            if not re.search(rf'^{variable_name}$', out, re.MULTILINE):
+                return None
+        mlog.debug(f'Got pkg-config variable {variable_name} : {variable}')
+        return variable
 
-        try:
-            # Fetch cargs to be used while using this dependency
-            self._set_cargs()
-            # Fetch the libraries and library paths needed for using this
-            self._set_libs()
-        except DependencyException as e:
-            mlog.debug(f"pkg-config error with '{name}': {e}")
-            if self.required:
-                raise
-            else:
-                self.compile_args = []
-                self.link_args = []
-                self.is_found = False
-                self.reason = e
+    def list_all(self) -> T.List[str]:
+        ret, out, err = self._call_pkgbin(['--list-all'])
+        if ret != 0:
+            raise DependencyException(f'could not list modules:\n{err}\n')
+        return [i.split(' ', 1)[0] for i in out.splitlines()]
 
-    def __repr__(self) -> str:
-        s = '<{0} {1}: {2} {3}>'
-        return s.format(self.__class__.__name__, self.name, self.is_found,
-                        self.version_reqs)
+    def _split_args(self, cmd: str) -> T.List[str]:
+        # pkg-config paths follow Unix conventions, even on Windows; split the
+        # output using shlex.split rather than mesonlib.split_args
+        return shlex.split(cmd)
 
     @classmethod
-    def _detect_pkgbin(cls, silent: bool, env: Environment,
-                       for_machine: MachineChoice) -> T.Union[None, bool, ExternalProgram]:
+    def _detect_pkgbin(cls, env: Environment, for_machine: MachineChoice, silent: bool) -> T.Optional[ExternalProgram]:
         # Only search for pkg-config for each machine the first time and store
         # the result in the class definition
         if cls.class_pkgbin[for_machine] is False:
@@ -111,12 +189,12 @@ class PkgConfigDependency(ExternalDependency):
                 break
             else:
                 if not silent:
-                    mlog.log('Found Pkg-config:', mlog.red('NO'))
+                    mlog.log('Found pkg-config:', mlog.red('NO'))
                 # Set to False instead of None to signify that we've already
                 # searched for it and not found it
                 cls.class_pkgbin[for_machine] = False
 
-        return cls.class_pkgbin[for_machine]
+        return cls.class_pkgbin[for_machine] or None
 
     def _call_pkgbin_real(self, args: T.List[str], env: T.Dict[str, str]) -> T.Tuple[int, str, str]:
         assert isinstance(self.pkgbin, ExternalProgram)
@@ -125,8 +203,34 @@ class PkgConfigDependency(ExternalDependency):
         return p.returncode, out.strip(), err.strip()
 
     @staticmethod
-    def get_env(environment: 'Environment', for_machine: MachineChoice,
-                uninstalled: bool = False) -> 'EnvironmentVariables':
+    def check_pkgconfig(env: Environment, pkgbin: ExternalProgram) -> T.Optional[str]:
+        if not pkgbin.found():
+            mlog.log(f'Did not find pkg-config by name {pkgbin.name!r}')
+            return None
+        command_as_string = ' '.join(pkgbin.get_command())
+        try:
+            helptext = Popen_safe(pkgbin.get_command() + ['--help'])[1]
+            if 'Pure-Perl' in helptext:
+                mlog.log(f'Found pkg-config {command_as_string!r} but it is Strawberry Perl and thus broken. Ignoring...')
+                return None
+            p, out = Popen_safe(pkgbin.get_command() + ['--version'])[0:2]
+            if p.returncode != 0:
+                mlog.warning(f'Found pkg-config {command_as_string!r} but it failed when ran')
+                return None
+        except FileNotFoundError:
+            mlog.warning(f'We thought we found pkg-config {command_as_string!r} but now it\'s not there. How odd!')
+            return None
+        except PermissionError:
+            msg = f'Found pkg-config {command_as_string!r} but didn\'t have permissions to run it.'
+            if not env.machines.build.is_windows():
+                msg += '\n\nOn Unix-like systems this is often caused by scripts that are not executable.'
+            mlog.warning(msg)
+            return None
+        return out.strip()
+
+    @staticmethod
+    def get_env(environment: Environment, for_machine: MachineChoice,
+                uninstalled: bool = False) -> EnvironmentVariables:
         env = EnvironmentVariables()
         key = OptionKey('pkg_config_path', machine=for_machine)
         extra_paths: T.List[str] = environment.coredata.options[key].value[:]
@@ -144,9 +248,9 @@ class PkgConfigDependency(ExternalDependency):
         return env
 
     @staticmethod
-    def setup_env(env: EnvironOrDict, environment: 'Environment', for_machine: MachineChoice,
+    def setup_env(env: EnvironOrDict, environment: Environment, for_machine: MachineChoice,
                   uninstalled: bool = False) -> T.Dict[str, str]:
-        envvars = PkgConfigDependency.get_env(environment, for_machine, uninstalled)
+        envvars = PkgConfigCLI.get_env(environment, for_machine, uninstalled)
         env = envvars.get_env(env)
         # Dump all PKG_CONFIG environment variables
         for key, value in env.items():
@@ -157,15 +261,57 @@ class PkgConfigDependency(ExternalDependency):
     def _call_pkgbin(self, args: T.List[str], env: T.Optional[EnvironOrDict] = None) -> T.Tuple[int, str, str]:
         assert isinstance(self.pkgbin, ExternalProgram)
         env = env or os.environ
-        env = PkgConfigDependency.setup_env(env, self.env, self.for_machine)
+        env = self.setup_env(env, self.env, self.for_machine)
 
         fenv = frozenset(env.items())
         targs = tuple(args)
-        cache = PkgConfigDependency.pkgbin_cache
+        cache = self.pkgbin_cache
         if (self.pkgbin, targs, fenv) not in cache:
             cache[(self.pkgbin, targs, fenv)] = self._call_pkgbin_real(args, env)
         return cache[(self.pkgbin, targs, fenv)]
 
+
+class PkgConfigDependency(ExternalDependency):
+
+    def __init__(self, name: str, environment: Environment, kwargs: T.Dict[str, T.Any], language: T.Optional[str] = None) -> None:
+        super().__init__(DependencyTypeName('pkgconfig'), environment, kwargs, language=language)
+        self.name = name
+        self.is_libtool = False
+        self.pkgconfig = PkgConfigInterface.instance(self.env, self.for_machine, self.silent)
+        if not self.pkgconfig:
+            msg = f'Pkg-config for machine {self.for_machine} not found. Giving up.'
+            if self.required:
+                raise DependencyException(msg)
+            mlog.debug(msg)
+            return
+
+        version = self.pkgconfig.version(name)
+        if version is None:
+            return
+
+        self.version = version
+        self.is_found = True
+
+        try:
+            # Fetch cargs to be used while using this dependency
+            self._set_cargs()
+            # Fetch the libraries and library paths needed for using this
+            self._set_libs()
+        except DependencyException as e:
+            mlog.debug(f"Pkg-config error with '{name}': {e}")
+            if self.required:
+                raise
+            else:
+                self.compile_args = []
+                self.link_args = []
+                self.is_found = False
+                self.reason = e
+
+    def __repr__(self) -> str:
+        s = '<{0} {1}: {2} {3}>'
+        return s.format(self.__class__.__name__, self.name, self.is_found,
+                        self.version_reqs)
+
     def _convert_mingw_paths(self, args: T.List[str]) -> T.List[str]:
         '''
         Both MSVC and native Python on Windows cannot handle MinGW-esque /c/foo
@@ -197,27 +343,19 @@ class PkgConfigDependency(ExternalDependency):
             converted.append(arg)
         return converted
 
-    def _split_args(self, cmd: str) -> T.List[str]:
-        # pkg-config paths follow Unix conventions, even on Windows; split the
-        # output using shlex.split rather than mesonlib.split_args
-        return shlex.split(cmd)
-
     def _set_cargs(self) -> None:
-        env = None
+        allow_system = False
         if self.language == 'fortran':
             # gfortran doesn't appear to look in system paths for INCLUDE files,
             # so don't allow pkg-config to suppress -I flags for system paths
-            env = os.environ.copy()
-            env['PKG_CONFIG_ALLOW_SYSTEM_CFLAGS'] = '1'
-        ret, out, err = self._call_pkgbin(['--cflags', self.name], env=env)
-        if ret != 0:
-            raise DependencyException(f'Could not generate cargs for {self.name}:\n{err}\n')
-        self.compile_args = self._convert_mingw_paths(self._split_args(out))
+            allow_system = True
+        cflags = self.pkgconfig.cflags(self.name, allow_system)
+        self.compile_args = self._convert_mingw_paths(cflags)
 
-    def _search_libs(self, out: str, out_raw: str) -> T.Tuple[T.List[str], T.List[str]]:
+    def _search_libs(self, libs_in: T.List[str], raw_libs_in: T.List[str]) -> T.Tuple[T.List[str], T.List[str]]:
         '''
-        @out: PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 pkg-config --libs
-        @out_raw: pkg-config --libs
+        @libs_in: PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 pkg-config --libs
+        @raw_libs_in: pkg-config --libs
 
         We always look for the file ourselves instead of depending on the
         compiler to find it with -lfoo or foo.lib (if possible) because:
@@ -241,7 +379,7 @@ class PkgConfigDependency(ExternalDependency):
         # always searched first.
         prefix_libpaths: OrderedSet[str] = OrderedSet()
         # We also store this raw_link_args on the object later
-        raw_link_args = self._convert_mingw_paths(self._split_args(out_raw))
+        raw_link_args = self._convert_mingw_paths(raw_libs_in)
         for arg in raw_link_args:
             if arg.startswith('-L') and not arg.startswith(('-L-l', '-L-L')):
                 path = arg[2:]
@@ -262,7 +400,7 @@ class PkgConfigDependency(ExternalDependency):
         pkg_config_path = self._convert_mingw_paths(pkg_config_path)
         prefix_libpaths = OrderedSet(sort_libpaths(list(prefix_libpaths), pkg_config_path))
         system_libpaths: OrderedSet[str] = OrderedSet()
-        full_args = self._convert_mingw_paths(self._split_args(out))
+        full_args = self._convert_mingw_paths(libs_in)
         for arg in full_args:
             if arg.startswith(('-L-l', '-L-L')):
                 # These are D language arguments, not library paths
@@ -367,84 +505,25 @@ class PkgConfigDependency(ExternalDependency):
         return link_args, raw_link_args
 
     def _set_libs(self) -> None:
-        env = None
-        libcmd = ['--libs']
-
-        if self.static:
-            libcmd.append('--static')
-
-        libcmd.append(self.name)
-
         # Force pkg-config to output -L fields even if they are system
         # paths so we can do manual searching with cc.find_library() later.
-        env = os.environ.copy()
-        env['PKG_CONFIG_ALLOW_SYSTEM_LIBS'] = '1'
-        ret, out, err = self._call_pkgbin(libcmd, env=env)
-        if ret != 0:
-            raise DependencyException(f'Could not generate libs for {self.name}:\n{err}\n')
+        libs = self.pkgconfig.libs(self.name, self.static, allow_system=True)
         # Also get the 'raw' output without -Lfoo system paths for adding -L
         # args with -lfoo when a library can't be found, and also in
         # gnome.generate_gir + gnome.gtkdoc which need -L -l arguments.
-        ret, out_raw, err_raw = self._call_pkgbin(libcmd)
-        if ret != 0:
-            raise DependencyException(f'Could not generate libs for {self.name}:\n\n{out_raw}')
-        self.link_args, self.raw_link_args = self._search_libs(out, out_raw)
+        raw_libs = self.pkgconfig.libs(self.name, self.static, allow_system=False)
+        self.link_args, self.raw_link_args = self._search_libs(libs, raw_libs)
 
     def get_pkgconfig_variable(self, variable_name: str,
-                               define_variable: 'ImmutableListProtocol[str]',
+                               define_variable: ImmutableListProtocol[str],
                                default: T.Optional[str]) -> str:
-        options = ['--variable=' + variable_name, self.name]
-
-        if define_variable:
-            options = ['--define-variable=' + '='.join(define_variable)] + options
-
-        ret, out, err = self._call_pkgbin(options)
-        variable = ''
-        if ret != 0:
-            if self.required:
-                raise DependencyException(f'dependency {self.name} not found:\n{err}\n')
-        else:
-            variable = out.strip()
-
-            # pkg-config doesn't distinguish between empty and nonexistent variables
-            # use the variable list to check for variable existence
-            if not variable:
-                ret, out, _ = self._call_pkgbin(['--print-variables', self.name])
-                if not re.search(r'^' + variable_name + r'$', out, re.MULTILINE):
-                    if default is not None:
-                        variable = default
-                    else:
-                        mlog.warning(f"pkgconfig variable '{variable_name}' not defined for dependency {self.name}.")
-
-        mlog.debug(f'Got pkgconfig variable {variable_name} : {variable}')
+        variable = self.pkgconfig.variable(self.name, variable_name, define_variable)
+        if variable is None:
+            if default is None:
+                mlog.warning(f'Pkg-config variable {variable_name!r} not defined for dependency {self.name}.')
+            variable = default or ''
         return variable
 
-    @staticmethod
-    def check_pkgconfig(env: Environment, pkgbin: ExternalProgram) -> T.Optional[str]:
-        if not pkgbin.found():
-            mlog.log(f'Did not find pkg-config by name {pkgbin.name!r}')
-            return None
-        command_as_string = ' '.join(pkgbin.get_command())
-        try:
-            helptext = Popen_safe(pkgbin.get_command() + ['--help'])[1]
-            if 'Pure-Perl' in helptext:
-                mlog.log(f'found pkg-config {command_as_string!r} but it is Strawberry Perl and thus broken. Ignoring...')
-                return None
-            p, out = Popen_safe(pkgbin.get_command() + ['--version'])[0:2]
-            if p.returncode != 0:
-                mlog.warning(f'Found pkg-config {command_as_string!r} but it failed when run')
-                return None
-        except FileNotFoundError:
-            mlog.warning(f'We thought we found pkg-config {command_as_string!r} but now it\'s not there. How odd!')
-            return None
-        except PermissionError:
-            msg = f'Found pkg-config {command_as_string!r} but didn\'t have permissions to run it.'
-            if not env.machines.build.is_windows():
-                msg += '\n\nOn Unix-like systems this is often caused by scripts that are not executable.'
-            mlog.warning(msg)
-            return None
-        return out.strip()
-
     def extract_field(self, la_file: str, fieldname: str) -> T.Optional[str]:
         with open(la_file, encoding='utf-8') as f:
             for line in f:
diff --git a/mesonbuild/dependencies/scalapack.py b/mesonbuild/dependencies/scalapack.py
index 2442ede..fc2f720 100644
--- a/mesonbuild/dependencies/scalapack.py
+++ b/mesonbuild/dependencies/scalapack.py
@@ -20,7 +20,6 @@ import typing as T
 
 from ..mesonlib import OptionKey
 from .base import DependencyMethods
-from .base import DependencyException
 from .cmake import CMakeDependency
 from .detect import packages
 from .pkgconfig import PkgConfigDependency
@@ -144,17 +143,10 @@ class MKLPkgConfigDependency(PkgConfigDependency):
             self.link_args.insert(i + 1, '-lmkl_blacs_intelmpi_lp64')
 
     def _set_cargs(self) -> None:
-        env = None
+        allow_system = False
         if self.language == 'fortran':
             # gfortran doesn't appear to look in system paths for INCLUDE files,
             # so don't allow pkg-config to suppress -I flags for system paths
-            env = os.environ.copy()
-            env['PKG_CONFIG_ALLOW_SYSTEM_CFLAGS'] = '1'
-        ret, out, err = self._call_pkgbin([
-            '--cflags', self.name,
-            '--define-variable=prefix=' + self.__mklroot.as_posix()],
-            env=env)
-        if ret != 0:
-            raise DependencyException('Could not generate cargs for %s:\n%s\n' %
-                                      (self.name, err))
-        self.compile_args = self._convert_mingw_paths(self._split_args(out))
+            allow_system = True
+        cflags = self.pkgconfig.cflags(self.name, allow_system, define_variable=['prefix', self.__mklroot.as_posix()])
+        self.compile_args = self._convert_mingw_paths(cflags)
diff --git a/mesonbuild/modules/external_project.py b/mesonbuild/modules/external_project.py
index fd7e7c8..f7a72bc 100644
--- a/mesonbuild/modules/external_project.py
+++ b/mesonbuild/modules/external_project.py
@@ -24,7 +24,7 @@ from .. import mlog, build
 from ..compilers.compilers import CFLAGS_MAPPING
 from ..envconfig import ENV_VAR_PROG_MAP
 from ..dependencies import InternalDependency
-from ..dependencies.pkgconfig import PkgConfigDependency
+from ..dependencies.pkgconfig import PkgConfigCLI
 from ..interpreterbase import FeatureNew
 from ..interpreter.type_checking import ENV_KW, DEPENDS_KW
 from ..interpreterbase.decorators import ContainerTypeInfo, KwargInfo, typed_kwargs, typed_pos_args
@@ -165,8 +165,8 @@ class ExternalProject(NewExtensionModule):
         self.run_env['LDFLAGS'] = self._quote_and_join(link_args)
 
         self.run_env = self.user_env.get_env(self.run_env)
-        self.run_env = PkgConfigDependency.setup_env(self.run_env, self.env, MachineChoice.HOST,
-                                                     uninstalled=True)
+        self.run_env = PkgConfigCLI.setup_env(self.run_env, self.env, MachineChoice.HOST,
+                                              uninstalled=True)
 
         self.build_dir.mkdir(parents=True, exist_ok=True)
         self._run('configure', configure_cmd, workdir)
diff --git a/mesonbuild/modules/gnome.py b/mesonbuild/modules/gnome.py
index 3249212..18862e7 100644
--- a/mesonbuild/modules/gnome.py
+++ b/mesonbuild/modules/gnome.py
@@ -34,7 +34,7 @@ from .. import mesonlib
 from .. import mlog
 from ..build import CustomTarget, CustomTargetIndex, Executable, GeneratedList, InvalidArguments
 from ..dependencies import Dependency, InternalDependency
-from ..dependencies.pkgconfig import PkgConfigDependency
+from ..dependencies.pkgconfig import PkgConfigDependency, PkgConfigCLI
 from ..interpreter.type_checking import DEPENDS_KW, DEPEND_FILES_KW, ENV_KW, INSTALL_DIR_KW, INSTALL_KW, NoneType, SOURCES_KW, in_set_validator
 from ..interpreterbase import noPosargs, noKwargs, FeatureNew, FeatureDeprecated
 from ..interpreterbase import typed_kwargs, KwargInfo, ContainerTypeInfo
@@ -967,7 +967,7 @@ class GnomeModule(ExtensionModule):
         # -uninstalled.pc files Meson generated. It also must respect pkgconfig
         # settings user could have set in machine file, like PKG_CONFIG_LIBDIR,
         # SYSROOT, etc.
-        run_env = PkgConfigDependency.get_env(state.environment, MachineChoice.HOST, uninstalled=True)
+        run_env = PkgConfigCLI.get_env(state.environment, MachineChoice.HOST, uninstalled=True)
         # g-ir-scanner uses Python's distutils to find the compiler, which uses 'CC'
         cc_exelist = state.environment.coredata.compilers.host['c'].get_exelist()
         run_env.set('CC', [quote_arg(x) for x in cc_exelist], ' ')
diff --git a/mesonbuild/modules/pkgconfig.py b/mesonbuild/modules/pkgconfig.py
index dd2efad..44182d7 100644
--- a/mesonbuild/modules/pkgconfig.py
+++ b/mesonbuild/modules/pkgconfig.py
@@ -26,7 +26,7 @@ from .. import dependencies
 from .. import mesonlib
 from .. import mlog
 from ..coredata import BUILTIN_DIR_OPTIONS
-from ..dependencies.pkgconfig import PkgConfigDependency
+from ..dependencies.pkgconfig import PkgConfigDependency, PkgConfigCLI
 from ..interpreter.type_checking import D_MODULE_VERSIONS_KW, INSTALL_DIR_KW, VARIABLES_KW, NoneType
 from ..interpreterbase import FeatureNew, FeatureDeprecated
 from ..interpreterbase.decorators import ContainerTypeInfo, KwargInfo, typed_kwargs, typed_pos_args
@@ -741,7 +741,7 @@ class PkgConfigModule(NewExtensionModule):
                     self._metadata[lib.get_id()] = MetaData(
                         filebase, name, state.current_node)
         if self.devenv is None:
-            self.devenv = PkgConfigDependency.get_env(state.environment, mesonlib.MachineChoice.HOST, uninstalled=True)
+            self.devenv = PkgConfigCLI.get_env(state.environment, mesonlib.MachineChoice.HOST, uninstalled=True)
         return ModuleReturnValue(res, [res])
 
 
diff --git a/run_tests.py b/run_tests.py
index 66341e4..cf06337 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -36,7 +36,7 @@ import typing as T
 
 from mesonbuild.compilers.c import CCompiler
 from mesonbuild.compilers.detect import detect_c_compiler
-from mesonbuild.dependencies.pkgconfig import PkgConfigDependency
+from mesonbuild.dependencies.pkgconfig import PkgConfigCLI
 from mesonbuild import mesonlib
 from mesonbuild import mesonmain
 from mesonbuild import mtest
@@ -302,8 +302,8 @@ def run_mtest_inprocess(commandlist: T.List[str]) -> T.Tuple[int, str, str]:
 def clear_meson_configure_class_caches() -> None:
     CCompiler.find_library_cache = {}
     CCompiler.find_framework_cache = {}
-    PkgConfigDependency.pkgbin_cache = {}
-    PkgConfigDependency.class_pkgbin = mesonlib.PerMachine(None, None)
+    PkgConfigCLI.pkgbin_cache = {}
+    PkgConfigCLI.class_pkgbin = mesonlib.PerMachine(None, None)
     mesonlib.project_meson_versions = collections.defaultdict(str)
 
 def run_configure_inprocess(commandlist: T.List[str], env: T.Optional[T.Dict[str, str]] = None, catch_exception: bool = False) -> T.Tuple[int, str, str]:
diff --git a/unittests/internaltests.py b/unittests/internaltests.py
index 672a5a0..86a30f8 100644
--- a/unittests/internaltests.py
+++ b/unittests/internaltests.py
@@ -47,7 +47,7 @@ from mesonbuild.mesonlib import (
     OptionType
 )
 from mesonbuild.interpreter.type_checking import in_set_validator, NoneType
-from mesonbuild.dependencies.pkgconfig import PkgConfigDependency
+from mesonbuild.dependencies.pkgconfig import PkgConfigDependency, PkgConfigInterface, PkgConfigCLI
 from mesonbuild.programs import ExternalProgram
 import mesonbuild.modules.pkgconfig
 
@@ -640,22 +640,19 @@ class InternalTests(unittest.TestCase):
             create_static_lib(p1 / 'libdl.a')
             create_static_lib(p1 / 'librt.a')
 
-            def fake_call_pkgbin(self, args, env=None):
-                if '--libs' not in args:
-                    return 0, '', ''
-                if args[-1] == 'foo':
-                    return 0, f'-L{p2.as_posix()} -lfoo -L{p1.as_posix()} -lbar', ''
-                if args[-1] == 'bar':
-                    return 0, f'-L{p2.as_posix()} -lbar', ''
-                if args[-1] == 'internal':
-                    return 0, f'-L{p1.as_posix()} -lpthread -lm -lc -lrt -ldl', ''
-
-            old_call = PkgConfigDependency._call_pkgbin
-            old_check = PkgConfigDependency.check_pkgconfig
-            PkgConfigDependency._call_pkgbin = fake_call_pkgbin
-            PkgConfigDependency.check_pkgconfig = lambda x, _: pkgbin
-            # Test begins
-            try:
+            class FakeInstance(PkgConfigCLI):
+                def _call_pkgbin(self, args, env=None):
+                    if '--libs' not in args:
+                        return 0, '', ''
+                    if args[-1] == 'foo':
+                        return 0, f'-L{p2.as_posix()} -lfoo -L{p1.as_posix()} -lbar', ''
+                    if args[-1] == 'bar':
+                        return 0, f'-L{p2.as_posix()} -lbar', ''
+                    if args[-1] == 'internal':
+                        return 0, f'-L{p1.as_posix()} -lpthread -lm -lc -lrt -ldl', ''
+
+            with mock.patch.object(PkgConfigInterface, 'instance') as instance_method:
+                instance_method.return_value = FakeInstance(env, MachineChoice.HOST, silent=True)
                 kwargs = {'required': True, 'silent': True}
                 foo_dep = PkgConfigDependency('foo', env, kwargs)
                 self.assertEqual(foo_dep.get_link_args(),
@@ -670,13 +667,6 @@ class InternalTests(unittest.TestCase):
                     for link_arg in link_args:
                         for lib in ('pthread', 'm', 'c', 'dl', 'rt'):
                             self.assertNotIn(f'lib{lib}.a', link_arg, msg=link_args)
-            finally:
-                # Test ends
-                PkgConfigDependency._call_pkgbin = old_call
-                PkgConfigDependency.check_pkgconfig = old_check
-                # Reset dependency class to ensure that in-process configure doesn't mess up
-                PkgConfigDependency.pkgbin_cache = {}
-                PkgConfigDependency.class_pkgbin = PerMachine(None, None)
 
     def test_version_compare(self):
         comparefunc = mesonbuild.mesonlib.version_compare_many
diff --git a/unittests/linuxliketests.py b/unittests/linuxliketests.py
index 7ebb575..bd73857 100644
--- a/unittests/linuxliketests.py
+++ b/unittests/linuxliketests.py
@@ -45,7 +45,7 @@ from mesonbuild.compilers.c import AppleClangCCompiler
 from mesonbuild.compilers.cpp import AppleClangCPPCompiler
 from mesonbuild.compilers.objc import AppleClangObjCCompiler
 from mesonbuild.compilers.objcpp import AppleClangObjCPPCompiler
-from mesonbuild.dependencies.pkgconfig import PkgConfigDependency
+from mesonbuild.dependencies.pkgconfig import PkgConfigDependency, PkgConfigCLI
 import mesonbuild.modules.pkgconfig
 
 PKG_CONFIG = os.environ.get('PKG_CONFIG', 'pkg-config')
@@ -173,7 +173,8 @@ class LinuxlikeTests(BasePlatformTests):
         self.assertEqual(libhello_nolib.get_compile_args(), [])
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('foo', [], None), 'bar')
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('prefix', [], None), self.prefix)
-        if version_compare(PkgConfigDependency.check_pkgconfig(env, libhello_nolib.pkgbin),">=0.29.1"):
+        impl = libhello_nolib.pkgconfig
+        if not isinstance(impl, PkgConfigCLI) or version_compare(PkgConfigCLI.check_pkgconfig(env, impl.pkgbin),">=0.29.1"):
             self.assertEqual(libhello_nolib.get_pkgconfig_variable('escaped_var', [], None), r'hello\ world')
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('unescaped_var', [], None), 'hello world')
 
@@ -1168,7 +1169,7 @@ class LinuxlikeTests(BasePlatformTests):
 
         # Regression test: This used to modify the value of `pkg_config_path`
         # option, adding the meson-uninstalled directory to it.
-        PkgConfigDependency.setup_env({}, env, MachineChoice.HOST, uninstalled=True)
+        PkgConfigCLI.setup_env({}, env, MachineChoice.HOST, uninstalled=True)
 
         pkg_config_path = env.coredata.options[OptionKey('pkg_config_path')].value
         self.assertEqual(pkg_config_path, [pkg_dir])