Allow CustomTarget source for i18n.xgettext

Fixes #15054

6 files changed, 25 insertions, 3 deletions

diff --git a/docs/markdown/i18n-module.md b/docs/markdown/i18n-module.md
index ac6146dd5..6cdd74a28 100644
--- a/docs/markdown/i18n-module.md
+++ b/docs/markdown/i18n-module.md
@@ -90,7 +90,7 @@ for each executable.
 Positional arguments are the following:
 
 * name `str`: the name of the resulting pot file.
-* sources `array[str|File|build_tgt|custom_tgt]`:
+* sources `array[str|File|build_tgt|custom_tgt|custom_idx]`:
           source files or targets. May be a list of `string`, `File`, [[@build_tgt]],
           or [[@custom_tgt]] returned from other calls to this function.
 
@@ -120,4 +120,7 @@ included to generate the final pot file. Therefore, adding a dependency to
 source target will automatically add the translations of that dependency to the
 needed translations for that source target.
 
+*New in 1.10.0* sources can be result of [[@custom_tgt]] or [[@custom_idx]].
+Before 1.10.0, custom targets were silently ignored.
+
 *Added 1.8.0*
diff --git a/docs/markdown/snippets/xgettext-custom-tgt.md b/docs/markdown/snippets/xgettext-custom-tgt.md
new file mode 100644
index 000000000..37ec43823
--- /dev/null
+++ b/docs/markdown/snippets/xgettext-custom-tgt.md
@@ -0,0 +1,7 @@
+## `i18n.xgettext` now accepts CustomTarget and CustomTargetIndex as sources
+
+Previously, [[@custom_tgt]] were accepted but silently ignored, and
+[[@custom_idx]] were not accepted.
+
+Now, they both can be used, and the generated outputs will be scanned to extract
+translation strings.
diff --git a/mesonbuild/modules/i18n.py b/mesonbuild/modules/i18n.py
index 87baab203..8b8306584 100644
--- a/mesonbuild/modules/i18n.py
+++ b/mesonbuild/modules/i18n.py
@@ -75,7 +75,7 @@ if T.TYPE_CHECKING:
         install_dir: T.Optional[str]
         install_tag: T.Optional[str]
 
-    SourcesType = T.Union[str, mesonlib.File, build.BuildTarget, build.BothLibraries, build.CustomTarget]
+    SourcesType = T.Union[str, mesonlib.File, build.BuildTarget, build.BothLibraries, build.CustomTarget, build.CustomTargetIndex]
 
 
 _ARGS: KwargInfo[T.List[str]] = KwargInfo(
@@ -202,6 +202,8 @@ class XgettextProgram:
                 source_files.update(source.get_sources())
             elif isinstance(source, build.BothLibraries):
                 source_files.update(source.get('shared').get_sources())
+            elif isinstance(source, (build.CustomTarget, build.CustomTargetIndex)):
+                source_files.update(mesonlib.File.from_built_file(source.get_subdir(), f) for f in source.get_outputs())
         return source_files
 
     def _get_depends(self, sources: T.Iterable[SourcesType]) -> T.Set[build.CustomTarget]:
@@ -531,7 +533,7 @@ class I18nModule(ExtensionModule):
         return ModuleReturnValue(ct, [ct])
 
     @FeatureNew('i18n.xgettext', '1.8.0')
-    @typed_pos_args('i18n.xgettext', str, varargs=(str, mesonlib.File, build.BuildTarget, build.BothLibraries, build.CustomTarget), min_varargs=1)
+    @typed_pos_args('i18n.xgettext', str, varargs=(str, mesonlib.File, build.BuildTarget, build.BothLibraries, build.CustomTarget, build.CustomTargetIndex), min_varargs=1)
     @typed_kwargs(
         'i18n.xgettext',
         _ARGS,
@@ -541,6 +543,11 @@ class I18nModule(ExtensionModule):
         INSTALL_TAG_KW,
     )
     def xgettext(self, state: ModuleState, args: T.Tuple[str, T.List[SourcesType]], kwargs: XgettextProgramT) -> build.CustomTarget:
+        if any(isinstance(a, build.CustomTarget) for a in args[1]):
+            FeatureNew.single_use('i18n.xgettext with custom_target is broken until 1.10', '1.10.0', self.interpreter.subproject, location=self.interpreter.current_node)
+        if any(isinstance(a, build.CustomTargetIndex) for a in args[1]):
+            FeatureNew.single_use('i18n.xgettext with custom_target index', '1.10.0', self.interpreter.subproject, location=self.interpreter.current_node)
+
         toolname = 'xgettext'
         if self.tools[toolname] is None or not self.tools[toolname].found():
             self.tools[toolname] = state.find_program(toolname, required=True, for_machine=mesonlib.MachineChoice.BUILD)
diff --git a/test cases/frameworks/38 gettext extractor/src/lib3/foo.c b/test cases/frameworks/38 gettext extractor/src/lib3/foo.c
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/test cases/frameworks/38 gettext extractor/src/lib3/foo.c
diff --git a/test cases/frameworks/38 gettext extractor/src/lib3/meson.build b/test cases/frameworks/38 gettext extractor/src/lib3/meson.build
new file mode 100644
index 000000000..34afeeb4a
--- /dev/null
+++ b/test cases/frameworks/38 gettext extractor/src/lib3/meson.build
@@ -0,0 +1,4 @@
+fs = import('fs')
+
+foo = fs.copyfile('foo.c')
+i18n.xgettext('test', foo[0])
diff --git a/test cases/frameworks/38 gettext extractor/src/meson.build b/test cases/frameworks/38 gettext extractor/src/meson.build
index 27fc81326..b26646c1a 100644
--- a/test cases/frameworks/38 gettext extractor/src/meson.build
+++ b/test cases/frameworks/38 gettext extractor/src/meson.build
@@ -1,5 +1,6 @@
 subdir('lib1')
 subdir('lib2')
+subdir('lib3')
 
 main = executable('say', 'main.c', link_with: [lib2], include_directories: lib2_includes)