modules: fs: accept build targets as fs.copyfile() source

Allow CustomTarget, CustomTargetIndex, and BuildTarget as the first
argument to fs.copyfile(), so that build artifacts can be copied
without resorting to a manual custom_target.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

docs/markdown/Fs-module.md

@@ -259,7 +259,9 @@ returns:
 Copy a file from the source directory to the build directory at build time.
 
 Has the following positional arguments:
-   - src `File | str`: the file to copy
+   - src `File | str | build_tgt | custom_tgt | custom_idx`: the file to copy.
+     *Since 1.12.0* build targets, custom targets, and custom target indices are
+     also accepted.
 
 Has the following optional arguments:
    - dest `str`: the name of the output file. If unset will be the basename of

docs/markdown/snippets/fs-copyfile-build-targets.md

@@ -0,0 +1,5 @@
+## `fs.copyfile()` now accepts build targets as input
+
+`fs.copyfile()` now accepts `build_tgt`, `custom_tgt`, and `custom_idx`
+as the source argument, in addition to `File` and `str`. This makes it
+possible to copy build artifacts without resorting to a `custom_target`.

mesonbuild/modules/fs.py

@@ -280,7 +280,7 @@ class FSModule(ExtensionModule):
         return data
 
     @FeatureNew('fs.copyfile', '0.64.0')
-    @typed_pos_args('fs.copyfile', (File, str), optargs=[str])
+    @typed_pos_args('fs.copyfile', (File, str, CustomTarget, CustomTargetIndex, BuildTarget), optargs=[str])
     @typed_kwargs(
         'fs.copyfile',
         INSTALL_KW,
@@ -289,17 +289,28 @@ class FSModule(ExtensionModule):
         KwargInfo('install_dir', (str, NoneType)),
         BUILD_SUBDIR_KW.evolve(since='1.12.0'),
     )
-    def copyfile(self, state: ModuleState, args: T.Tuple[FileOrString, T.Optional[str]],
+    def copyfile(self, state: ModuleState, args: T.Tuple[T.Union[FileOrString, BuildTargetTypes], T.Optional[str]],
                  kwargs: CopyKw) -> ModuleReturnValue:
         """Copy a file into the build directory at build time."""
         if kwargs['install'] and not kwargs['install_dir']:
             raise InvalidArguments('"install_dir" must be specified when "install" is true')
 
-        src = self.interpreter.source_strings_to_files([args[0]])[0]
+        src: T.Union[File, BuildTarget, CustomTarget, CustomTargetIndex]
+        if isinstance(args[0], (CustomTarget, CustomTargetIndex, BuildTarget)):
+            FeatureNew.single_use('fs.copyfile with build_tgt, custom_tgt, and custom_idx', '1.12.0', state.subproject, location=state.current_node)
+            if isinstance(args[0], CustomTarget) and len(args[0].get_outputs()) > 1:
+                raise InvalidArguments(
+                    f'custom_target {args[0].name!r} has more than one output! '
+                    f'Use `{args[0].name}[<n>]` to select the output to copy.')
+            src = args[0]
+            default_name = src.get_filename()
+        else:
+            src = self.interpreter.source_strings_to_files([args[0]])[0]
+            # The input is allowed to have path separators, but the output may not,
+            # so use the basename for the default case
+            default_name = os.path.basename(src.fname)
 
-        # The input is allowed to have path separators, but the output may not,
-        # so use the basename for the default case
-        dest = args[1] if args[1] else os.path.basename(src.fname)
+        dest = args[1] if args[1] else default_name
         if has_path_sep(dest):
             raise InvalidArguments('Destination path may not have path separators')
 

test cases/common/220 fs module/meson.build

@@ -7,6 +7,9 @@ fs = import('fs')
 f = files('meson.build')
 btgt = executable('btgt', 'btgt.c')
 ctgt = fs.copyfile('ctgt.txt')
+ctgt_copy = fs.copyfile(ctgt, 'ctgt_copy.txt')
+ctgt_idx_copy = fs.copyfile(ctgt[0], 'ctgt_idx_copy.txt')
+btgt_copy = fs.copyfile(btgt, 'btgt_copy')
 
 assert(fs.exists('meson.build'), 'Existing file reported as missing.')
 assert(not fs.exists('nonexisting'), 'Nonexisting file was found.')
@@ -199,3 +202,13 @@ subproject('subbie')
 testcase expect_error('File notfound does not exist.')
   fs.read('notfound')
 endtestcase
+
+multi_out = custom_target('multi_out',
+  output: ['a.txt', 'b.txt'],
+  command: [find_program('cp'), '@INPUT@', '@OUTPUT@'],
+  input: 'meson.build',
+)
+
+testcase expect_error('custom_target \'multi_out\' has more than one output! Use `multi_out[<n>]` to select the output to copy.')
+  fs.copyfile(multi_out)
+endtestcase