pkgconfig: Use EnvironmentVariables to build PKG_CONFIG_* env

The new get_env() method that returns an EnvironmentVariables object
will be needed in next commit that will pass it to CustomTarget.

This has the side effect to use the proper os specific path separator
instead of hardcoding `:`. It is the obvious right thing to do here, but
has caused issues in the past. Hopefully issues have been fixed in the
meantime. If not, better deal with fallouts than keep doing the wrong
thing forever.

5 files changed, 36 insertions, 27 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index cb295bbef..3e7911f1c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -550,7 +550,7 @@ class EnvironmentVariables(HoldableObject):
         curr = env.get(name)
         return separator.join(values if curr is None else values + [curr])
 
-    def get_env(self, full_env: T.Dict[str, str]) -> T.Dict[str, str]:
+    def get_env(self, full_env: T.MutableMapping[str, str]) -> T.Dict[str, str]:
         env = full_env.copy()
         for method, name, values, separator in self.envvars:
             env[name] = method(env, name, values, separator)
diff --git a/mesonbuild/dependencies/pkgconfig.py b/mesonbuild/dependencies/pkgconfig.py
index 55a364cd1..e3f6e5c46 100644
--- a/mesonbuild/dependencies/pkgconfig.py
+++ b/mesonbuild/dependencies/pkgconfig.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 from __future__ import annotations
 
+from pathlib import Path
+
 from .base import ExternalDependency, DependencyException, sort_libpaths, DependencyTypeName
 from ..mesonlib import OptionKey, OrderedSet, PerMachine, Popen_safe
 from ..programs import find_external_program, ExternalProgram
@@ -27,6 +29,7 @@ if T.TYPE_CHECKING:
     from ..environment import Environment
     from ..mesonlib import MachineChoice
     from .._typing import ImmutableListProtocol
+    from ..build import EnvironmentVariables
 
 class PkgConfigDependency(ExternalDependency):
     # The class's copy of the pkg-config path. Avoids having to search for it
@@ -122,36 +125,40 @@ class PkgConfigDependency(ExternalDependency):
         return rc, out, err
 
     @staticmethod
-    def setup_env(env: T.MutableMapping[str, str], environment: 'Environment', for_machine: MachineChoice,
-                  extra_path: T.Optional[str] = None) -> None:
-        extra_paths: T.List[str] = environment.coredata.options[OptionKey('pkg_config_path', machine=for_machine)].value[:]
-        if extra_path and extra_path not in extra_paths:
-            extra_paths.append(extra_path)
+    def get_env(environment: 'Environment', for_machine: MachineChoice,
+                uninstalled: bool = False) -> 'EnvironmentVariables':
+        from ..build import EnvironmentVariables
+        env = EnvironmentVariables()
+        key = OptionKey('pkg_config_path', machine=for_machine)
+        extra_paths: T.List[str] = environment.coredata.options[key].value[:]
+        if uninstalled:
+            uninstalled_path = Path(environment.get_build_dir(), 'meson-uninstalled').as_posix()
+            if uninstalled_path not in extra_paths:
+                extra_paths.append(uninstalled_path)
+        env.set('PKG_CONFIG_PATH', extra_paths)
         sysroot = environment.properties[for_machine].get_sys_root()
         if sysroot:
-            env['PKG_CONFIG_SYSROOT_DIR'] = sysroot
-        new_pkg_config_path = ':'.join([p for p in extra_paths])
-        env['PKG_CONFIG_PATH'] = new_pkg_config_path
-
+            env.set('PKG_CONFIG_SYSROOT_DIR', [sysroot])
         pkg_config_libdir_prop = environment.properties[for_machine].get_pkg_config_libdir()
         if pkg_config_libdir_prop:
-            new_pkg_config_libdir = ':'.join([p for p in pkg_config_libdir_prop])
-            env['PKG_CONFIG_LIBDIR'] = new_pkg_config_libdir
+            env.set('PKG_CONFIG_LIBDIR', pkg_config_libdir_prop)
+        return env
+
+    @staticmethod
+    def setup_env(env: T.MutableMapping[str, str], environment: 'Environment', for_machine: MachineChoice,
+                  uninstalled: bool = False) -> T.Dict[str, str]:
+        envvars = PkgConfigDependency.get_env(environment, for_machine, uninstalled)
+        env = envvars.get_env(env)
         # Dump all PKG_CONFIG environment variables
         for key, value in env.items():
             if key.startswith('PKG_'):
                 mlog.debug(f'env[{key}]: {value}')
+        return env
 
-    def _call_pkgbin(self, args: T.List[str], env: T.Optional[T.Dict[str, str]] = None) -> T.Tuple[int, str, str]:
-        # Always copy the environment since we're going to modify it
-        # with pkg-config variables
-        if env is None:
-            env = os.environ.copy()
-        else:
-            env = env.copy()
-
+    def _call_pkgbin(self, args: T.List[str], env: T.Optional[T.MutableMapping[str, str]] = None) -> T.Tuple[int, str, str]:
         assert isinstance(self.pkgbin, ExternalProgram)
-        PkgConfigDependency.setup_env(env, self.env, self.for_machine)
+        env = env or os.environ
+        env = PkgConfigDependency.setup_env(env, self.env, self.for_machine)
 
         fenv = frozenset(env.items())
         targs = tuple(args)
diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index 5e8575a43..32141c9a4 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -654,7 +654,7 @@ class Environment:
                         _p_env = re.split(r':|;', p_env)
                     p_list = list(mesonlib.OrderedSet(_p_env))
                 elif keyname == 'pkg_config_path':
-                    p_list = list(mesonlib.OrderedSet(p_env.split(':')))
+                    p_list = list(mesonlib.OrderedSet(p_env.split(os.pathsep)))
                 else:
                     p_list = split_args(p_env)
                 p_list = [e for e in p_list if e]  # filter out any empty elements
diff --git a/mesonbuild/modules/unstable_external_project.py b/mesonbuild/modules/unstable_external_project.py
index d2c5b22e5..33a44d938 100644
--- a/mesonbuild/modules/unstable_external_project.py
+++ b/mesonbuild/modules/unstable_external_project.py
@@ -155,9 +155,8 @@ class ExternalProject(NewExtensionModule):
         self.run_env['LDFLAGS'] = self._quote_and_join(link_args)
 
         self.run_env = self.user_env.get_env(self.run_env)
-
-        PkgConfigDependency.setup_env(self.run_env, self.env, MachineChoice.HOST,
-                                      Path(self.env.get_build_dir(), 'meson-uninstalled').as_posix())
+        self.run_env = PkgConfigDependency.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/unittests/linuxliketests.py b/unittests/linuxliketests.py
index 2177cdd5a..ed6c95952 100644
--- a/unittests/linuxliketests.py
+++ b/unittests/linuxliketests.py
@@ -1152,9 +1152,12 @@ class LinuxlikeTests(BasePlatformTests):
         env = get_fake_env(testdir, self.builddir, self.prefix)
         env.coredata.set_options({OptionKey('pkg_config_path'): pkg_dir}, subproject='')
 
-        PkgConfigDependency.setup_env({}, env, MachineChoice.HOST, pkg_dir)
+        # 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)
+
         pkg_config_path = env.coredata.options[OptionKey('pkg_config_path')].value
-        self.assertEqual(len(pkg_config_path), 1)
+        self.assertEqual(pkg_config_path, [pkg_dir])
 
     @skipIfNoPkgconfig
     def test_pkgconfig_internal_libraries(self):