fs configure_file_list function

This function produces, at build time, a file containing the list of
files given as argument. It is used when a command uses, as argument, a file
containing the list of files to process. One usecase is to provide to `xgettext` the
list of files to process, from the list of source files, when this list is too
long to be provided to the command line as individual files.

docs/markdown/Fs-module.md

@@ -264,3 +264,32 @@ returns:
 ```meson
 copy = fs.copyfile('input-file', 'output-file')
 ```
+
+### configure_file_list
+
+*Since 1.4.0*
+
+Write paths from a list of files to a configuration file, to be used as argument
+to a command. The result file is generated at build time, and is updated when
+any input file is updated.
+
+Has the following positional arguments:
+   - name `str`: name of the resulting file
+   - sources `str | file | custom_tgt | custom_idx | build_tgt`: file paths to
+     write to the result file
+
+Has the following keyword arguments:
+   - quote `bool`: if `true`, add quote and escape chars to the file paths
+     (default `false`)
+   - separator `str`: characters used to separate the paths (default `\n`)
+   - end `str`: characters to put at the end of the file (default `\n`)
+   - relative_paths `bool`: if `true`, write relative paths, if `false`, write
+     absolute paths (default: `false`)
+
+returns:
+   - a [[custom_target]] object
+
+```meson
+src_files = files(...)
+file_list = fs.configure_file_list('filelist.txt', src_files)
+```

docs/markdown/snippets/fs_configure_file_list.md

@@ -0,0 +1,7 @@
+## `fs.configure_file_list()`
+
+This function produces, at build time, a file containing the list of files given
+as argument. It is used when a command uses, as argument, a file containing the
+list of files to process. One usecase is to provide to `xgettext` the list of
+files to process, from the list of source files, when this list is too long to
+be provided to the command line as individual files.

mesonbuild/modules/fs.py

@@ -12,7 +12,7 @@
 from ..build import BuildTarget, CustomTarget, CustomTargetIndex, InvalidArguments
 from ..interpreter.type_checking import INSTALL_KW, INSTALL_MODE_KW, INSTALL_TAG_KW, NoneType
 from ..interpreterbase import FeatureNew, KwargInfo, typed_kwargs, typed_pos_args, noKwargs
-from ..mesonlib import File, MesonException, has_path_sep, path_is_in_root, relpath
+from ..mesonlib import File, MesonException, has_path_sep, path_is_in_root, relpath, quote_arg
 
 if T.TYPE_CHECKING:
     from . import ModuleState
@@ -37,6 +37,13 @@ class CopyKw(TypedDict):
         install_mode: FileMode
         install_tag: T.Optional[str]
 
+    class ConfigureFileListKw(TypedDict):
+
+        quote: bool
+        separator: str
+        end: str
+        relative_paths: bool
+
 
 class FSModule(ExtensionModule):
 
@@ -62,6 +69,7 @@ def __init__(self, interpreter: 'Interpreter') -> None:
             'read': self.read,
             'copyfile': self.copyfile,
             'relative_to': self.relative_to,
+            'configure_file_list': self.configure_file_list,
         })
 
     def _absolute_dir(self, state: 'ModuleState', arg: 'FileOrString') -> Path:
@@ -317,6 +325,69 @@ def to_path(arg: T.Union[FileOrString, CustomTarget, CustomTargetIndex, BuildTar
 
         return relpath(t, f)
 
+    @FeatureNew('fs.configure_file_list', '1.4.0')
+    @typed_pos_args('fs.configure_file_list', str, varargs=(str, File, CustomTarget, CustomTargetIndex, BuildTarget))
+    @typed_kwargs(
+        'fs.configure_file_list',
+        KwargInfo('quote', bool, default=False),
+        KwargInfo('separator', str, default='\n'),
+        KwargInfo('end', str, default='\n'),
+        KwargInfo('relative_paths', bool, default=False),
+    )
+    def configure_file_list(self, state: ModuleState, args: T.Tuple[str, T.List[T.Union[FileOrString, BuildTargetTypes]]], kwargs: ConfigureFileListKw) -> ModuleReturnValue:
+        current_build_dir = Path(state.environment.build_dir, state.subdir)
+        file_list_dir = current_build_dir / 'file_list.p'
+        file_list_dir.mkdir(exist_ok=True)
+        name = args[0]
+
+        input_file = file_list_dir / name
+        output_file = current_build_dir / name
+
+        separator = kwargs['separator']
+        is_relative = kwargs['relative_paths']
+        quote = kwargs['quote']
+
+        # We generate the output now because we know how...
+        sources = args[1].copy()
+        nargs = len(sources)
+        with input_file.open('w', encoding='utf-8') as f:
+            for i, a in enumerate(sources, 1):
+                if isinstance(a, str):
+                    a = File(False, state.subdir, a)
+
+                elif isinstance(a, (BuildTarget, CustomTarget, CustomTargetIndex)):
+                    a = File(True, a.get_subdir(), a.get_outputs()[0])
+
+                assert isinstance(a, File), 'for mypy'
+                if is_relative:
+                    line = a.relative_name()
+                else:
+                    line = a.absolute_path(state.environment.source_dir, state.environment.build_dir)
+
+                if quote:
+                    line = quote_arg(line)
+
+                if i == nargs:
+                    separator = kwargs['end']
+                print(line, end=separator, file=f)
+
+        sources.insert(0, input_file.as_posix())
+
+        # ...but we copy it later, to ensure it is touched when an input is modified
+        ct = CustomTarget(
+            name,
+            state.subdir,
+            state.subproject,
+            state.environment,
+            state.environment.get_build_command() + ['--internal', 'copy', '@INPUT0@', '@OUTPUT@'],
+            sources,
+            [output_file.name],
+            build_by_default=True,
+            backend=state.backend,
+            description='Generating file list {}',
+        )
+        return ModuleReturnValue(ct, [ct])
+
 
 def initialize(*args: T.Any, **kwargs: T.Any) -> FSModule:
     return FSModule(*args, **kwargs)

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

@@ -168,6 +168,21 @@ subdir('subdir')
 
 subproject('subbie')
 
+
+# configure_file_list
+test_file_list = find_program('testfilelist.py')
+cfl = fs.configure_file_list(
+  'fl.txt',
+  'meson.build',
+  subdirfiles,
+  [btgt, ctgt],
+)
+test(
+  'fs.configure_file_list',
+  test_file_list,
+  args: cfl,
+)
+
 testcase expect_error('File notfound does not exist.')
   fs.read('notfound')
 endtestcase

test cases/common/220 fs module/testfilelist.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+
+import sys
+from pathlib import Path
+
+input_file = Path(sys.argv[-1])
+if not input_file.exists():
+    sys.exit('Input file not found')
+
+with input_file.open('r', encoding='utf-8') as f:
+    for line in f:
+        line = line.strip()
+        if not Path(line).exists():
+            sys.exit(f'File {line} not found')
+
+sys.exit(0)