pkgconfig: Add support for CustomTarget objects in generator

Fixes: #8618.

7 files changed, 60 insertions, 9 deletions

diff --git a/docs/markdown/Pkgconfig-module.md b/docs/markdown/Pkgconfig-module.md
index 35396d6..9c66b33 100644
--- a/docs/markdown/Pkgconfig-module.md
+++ b/docs/markdown/Pkgconfig-module.md
@@ -30,11 +30,14 @@ keyword arguments.
   also be provided and they will be added into the `Libs` field. Since 0.45.0
   dependencies of built libraries will be automatically added, see the
   [Implicit dependencies](#implicit-dependencies) section below for the exact
-  rules.
+  rules. Since 0.58.0 custom_target() objects are supported as long as they are
+  linkable (has known extension such as `.a`, `.so`, etc).
 - `libraries_private` list of built libraries or strings to put in the
   `Libs.private` field. Since 0.45.0 dependencies of built libraries will be
   automatically added, see the [Implicit dependencies](#implicit-dependencies)
-  section below for the exact rules.
+  section below for the exact rules. Since 0.58.0 custom_target() objects are
+  supported as long as they are linkable (has known extension such as `.a`,
+  `.so`, etc).
 - `name` the name of this library, used to set the `Name:` field
 - `subdirs` which subdirs of `include` should be added to the header
   search path, for example if you install headers into
diff --git a/docs/markdown/snippets/pkgconfig_gen_ct.md b/docs/markdown/snippets/pkgconfig_gen_ct.md
new file mode 100644
index 0000000..ccf9415
--- /dev/null
+++ b/docs/markdown/snippets/pkgconfig_gen_ct.md
@@ -0,0 +1,5 @@
+## Passing `custom_target()` output to `pkg.generate()`
+
+It is now allowed to pass libraries generated by a `custom_target()` to
+pkg-config file generator. The output filename must have a known library extension
+such as `.a`, `.so`, etc.
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 69e853f..06e40f5 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -2601,6 +2601,9 @@ class CustomTargetIndex:
     def extract_all_objects_recurse(self):
         return self.target.extract_all_objects_recurse()
 
+    def get_custom_install_dir(self):
+        return self.target.get_custom_install_dir()
+
 class ConfigurationData:
     def __init__(self) -> None:
         super().__init__()
diff --git a/mesonbuild/modules/pkgconfig.py b/mesonbuild/modules/pkgconfig.py
index 3f06ed0..18815f6 100644
--- a/mesonbuild/modules/pkgconfig.py
+++ b/mesonbuild/modules/pkgconfig.py
@@ -153,6 +153,11 @@ class DependenciesHelper:
                                            obj.link_whole_targets,
                                            obj.external_deps,
                                            isinstance(obj, build.StaticLibrary) and public)
+            elif isinstance(obj, (build.CustomTarget, build.CustomTargetIndex)):
+                if not obj.is_linkable_target():
+                    raise mesonlib.MesonException('library argument contains a not linkable custom_target.')
+                FeatureNew.single_use('custom_target in pkgconfig.generate libraries', '0.58.0', self.state.subproject)
+                processed_libs.append(obj)
             elif isinstance(obj, str):
                 processed_libs.append(obj)
             else:
@@ -276,7 +281,13 @@ class DependenciesHelper:
 
 class PkgConfigModule(ExtensionModule):
 
-    def _get_lname(self, l, msg, pcfile):
+    def _get_lname(self, l, msg, pcfile, is_custom_target):
+        if is_custom_target:
+            basename = os.path.basename(l.get_filename())
+            name = os.path.splitext(basename)[0]
+            if name.startswith('lib'):
+                name = name[3:]
+            return name
         # Nothing special
         if not l.name_prefix_set:
             return l.name
@@ -373,7 +384,8 @@ class PkgConfigModule(ExtensionModule):
                             install_dir = l.get_custom_install_dir()[0]
                         if install_dir is False:
                             continue
-                        if 'cs' in l.compilers:
+                        is_custom_target = isinstance(l, (build.CustomTarget, build.CustomTargetIndex))
+                        if not is_custom_target and 'cs' in l.compilers:
                             if isinstance(install_dir, str):
                                 Lflag = '-r${{prefix}}/{}/{}'.format(self._escape(self._make_relative(prefix, install_dir)), l.filename)
                             else:  # install_dir is True
@@ -386,18 +398,18 @@ class PkgConfigModule(ExtensionModule):
                         if Lflag not in Lflags:
                             Lflags.append(Lflag)
                             yield Lflag
-                        lname = self._get_lname(l, msg, pcfile)
+                        lname = self._get_lname(l, msg, pcfile, is_custom_target)
                         # If using a custom suffix, the compiler may not be able to
                         # find the library
-                        if l.name_suffix_set:
+                        if not is_custom_target and l.name_suffix_set:
                             mlog.warning(msg.format(l.name, 'name_suffix', lname, pcfile))
-                        if 'cs' not in l.compilers:
+                        if is_custom_target or 'cs' not in l.compilers:
                             yield '-l%s' % lname
 
             def get_uninstalled_include_dirs(libs):
                 result = []
                 for l in libs:
-                    if isinstance(l, str):
+                    if isinstance(l, (str, build.CustomTarget, build.CustomTargetIndex)):
                         continue
                     if l.get_subdir() not in result:
                         result.append(l.get_subdir())
diff --git a/run_unittests.py b/run_unittests.py
index 2a2fb4c..b6e349d 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -6486,6 +6486,13 @@ class LinuxlikeTests(BasePlatformTests):
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('foo', {}), 'bar')
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('prefix', {}), self.prefix)
 
+        cc = env.detect_c_compiler(MachineChoice.HOST)
+        if cc.get_id() in {'gcc', 'clang'}:
+            for name in {'ct', 'ct0'}:
+                ct_dep = PkgConfigDependency(name, env, kwargs)
+                self.assertTrue(ct_dep.found())
+                self.assertIn('-lct', ct_dep.get_link_args())
+
     def test_pkgconfig_gen_deps(self):
         '''
         Test that generated pkg-config files correctly handle dependencies
diff --git a/test cases/common/45 pkgconfig-gen/meson.build b/test cases/common/45 pkgconfig-gen/meson.build
index 6a3b788..7885391 100644
--- a/test cases/common/45 pkgconfig-gen/meson.build
+++ b/test cases/common/45 pkgconfig-gen/meson.build
@@ -101,3 +101,22 @@ stat2 = static_library('stat2', 'simple.c', install: true)
 simple4 = library('simple4', 'simple.c', link_with: stat2)
 simple5 = library('simple5', 'simple5.c', link_with: simple4, link_whole: stat2)
 pkgg.generate(simple5)
+
+# Test passing a linkable CustomTarget and CustomTargetIndex to generator.
+# Do this only with gcc/clang to not have to deal with other compiler command
+# line specificities.
+if cc.get_id() in ['gcc', 'clang']
+  ct = custom_target('ct',
+    input: 'simple.c',
+    output: 'libct.so',
+    command: [cc.cmd_array(), '@INPUT@', '-shared', '-o', '@OUTPUT@'],
+  )
+  pkgg.generate(libraries: ct,
+    name: 'ct',
+    description: 'custom target'
+  )
+  pkgg.generate(libraries: ct[0],
+    name: 'ct0',
+    description: 'custom target index'
+  )
+endif
diff --git a/test cases/common/45 pkgconfig-gen/test.json b/test cases/common/45 pkgconfig-gen/test.json
index 702e7fe..e741a62 100644
--- a/test cases/common/45 pkgconfig-gen/test.json
+++ b/test cases/common/45 pkgconfig-gen/test.json
@@ -8,6 +8,8 @@
     {"type": "file", "file": "usr/lib/pkgconfig/libhello_nolib.pc"},
     {"type": "file", "file": "usr/lib/pkgconfig/simple2.pc"},
     {"type": "file", "file": "usr/lib/pkgconfig/simple3.pc"},
-    {"type": "file", "file": "usr/lib/pkgconfig/simple5.pc"}
+    {"type": "file", "file": "usr/lib/pkgconfig/simple5.pc"},
+    {"type": "file", "file": "usr/lib/pkgconfig/ct.pc"},
+    {"type": "file", "file": "usr/lib/pkgconfig/ct0.pc"}
   ]
 }