install_{data,headers,subdir}: implement follow_symlinks

This permits users who rely on following symlinks to stay on the old
default of following them.

docs/markdown/snippets/install_follow_symlink_arg.md

@@ -0,0 +1,7 @@
+## Added follow_symlinks arg to install_data, install_header, and install_subdir
+
+The [[install_data]], [[install_headers]], [[install_subdir]] functions now
+have an optional argument `follow_symlinks` that, if set to `true`, makes it so
+symbolic links in the source are followed, rather than copied into the
+destination tree, to match the old behavior.  The default, which is currently
+to follow links, is subject to change in the future.

docs/yaml/functions/install_data.yaml

@@ -69,3 +69,11 @@ kwargs:
   sources:
     type: list[file | str]
     description: Additional files to install.
+
+  follow_symlinks:
+    type: bool
+    since: 1.3.0
+    default: true
+    description: |
+      If true, dereferences links and copies their target instead.  The default
+      value will become false in the future.

docs/yaml/functions/install_headers.yaml

@@ -73,3 +73,11 @@ kwargs:
       Disable stripping child-directories from header files when installing.
 
       This is equivalent to GNU Automake's `nobase` option.
+
+  follow_symlinks:
+    type: bool
+    since: 1.3.0
+    default: true
+    description: |
+      If true, dereferences links and copies their target instead.  The default
+      value will become false in the future.

docs/yaml/functions/install_subdir.yaml

@@ -106,3 +106,11 @@ kwargs:
     description: |
       Install directory contents.
       If `strip_directory=true` only the last component of the source path is used.
+
+  follow_symlinks:
+    type: bool
+    since: 1.3.0
+    default: true
+    description: |
+      If true, dereferences links and copies their target instead.  The default
+      value will become false in the future.

mesonbuild/backend/backends.py

@@ -172,6 +172,7 @@ class InstallDataBase:
     subproject: str
     tag: T.Optional[str] = None
     data_type: T.Optional[str] = None
+    follow_symlinks: T.Optional[bool] = None
 
 @dataclass(eq=False)
 class InstallSymlinkData:
@@ -186,8 +187,9 @@ class InstallSymlinkData:
 class SubdirInstallData(InstallDataBase):
     def __init__(self, path: str, install_path: str, install_path_name: str,
                  install_mode: 'FileMode', exclude: T.Tuple[T.Set[str], T.Set[str]],
-                 subproject: str, tag: T.Optional[str] = None, data_type: T.Optional[str] = None):
-        super().__init__(path, install_path, install_path_name, install_mode, subproject, tag, data_type)
+                 subproject: str, tag: T.Optional[str] = None, data_type: T.Optional[str] = None,
+                 follow_symlinks: T.Optional[bool] = None):
+        super().__init__(path, install_path, install_path_name, install_mode, subproject, tag, data_type, follow_symlinks)
         self.exclude = exclude
 
 
@@ -1832,7 +1834,7 @@ class Backend:
                 if not isinstance(f, File):
                     raise MesonException(f'Invalid header type {f!r} can\'t be installed')
                 abspath = f.absolute_path(srcdir, builddir)
-                i = InstallDataBase(abspath, outdir, outdir_name, h.get_custom_install_mode(), h.subproject, tag='devel')
+                i = InstallDataBase(abspath, outdir, outdir_name, h.get_custom_install_mode(), h.subproject, tag='devel', follow_symlinks=h.follow_symlinks)
                 d.headers.append(i)
 
     def generate_man_install(self, d: InstallData) -> None:
@@ -1877,7 +1879,8 @@ class Backend:
                 dstdir_name = os.path.join(subdir_name, dst_name)
                 tag = de.install_tag or self.guess_install_tag(dst_abs)
                 i = InstallDataBase(src_file.absolute_path(srcdir, builddir), dst_abs, dstdir_name,
-                                    de.install_mode, de.subproject, tag=tag, data_type=de.data_type)
+                                    de.install_mode, de.subproject, tag=tag, data_type=de.data_type,
+                                    follow_symlinks=de.follow_symlinks)
                 d.data.append(i)
 
     def generate_symlink_install(self, d: InstallData) -> None:
@@ -1908,7 +1911,8 @@ class Backend:
                 dst_dir = os.path.join(dst_dir, os.path.basename(src_dir))
                 dst_name = os.path.join(dst_name, os.path.basename(src_dir))
             tag = sd.install_tag or self.guess_install_tag(os.path.join(sd.install_dir, 'dummy'))
-            i = SubdirInstallData(src_dir, dst_dir, dst_name, sd.install_mode, sd.exclude, sd.subproject, tag)
+            i = SubdirInstallData(src_dir, dst_dir, dst_name, sd.install_mode, sd.exclude, sd.subproject, tag,
+                                  follow_symlinks=sd.follow_symlinks)
             d.install_subdirs.append(i)
 
     def get_introspection_data(self, target_id: str, target: build.Target) -> T.List['TargetIntrospectionData']:

mesonbuild/build.py

@@ -156,6 +156,7 @@ class Headers(HoldableObject):
     custom_install_dir: T.Optional[str]
     custom_install_mode: 'FileMode'
     subproject: str
+    follow_symlinks: T.Optional[bool] = None
 
     # TODO: we really don't need any of these methods, but they're preserved to
     # keep APIs relying on them working.
@@ -214,6 +215,7 @@ class InstallDir(HoldableObject):
     subproject: str
     from_source_dir: bool = True
     install_tag: T.Optional[str] = None
+    follow_symlinks: T.Optional[bool] = None
 
 @dataclass(eq=False)
 class DepManifest:
@@ -2973,6 +2975,7 @@ class Data(HoldableObject):
     rename: T.List[str] = None
     install_tag: T.Optional[str] = None
     data_type: str = None
+    follow_symlinks: T.Optional[bool] = None
 
     def __post_init__(self) -> None:
         if self.rename is None:

mesonbuild/interpreter/interpreter.py

@@ -78,6 +78,7 @@ from .type_checking import (
     INSTALL_KW,
     INSTALL_DIR_KW,
     INSTALL_MODE_KW,
+    INSTALL_FOLLOW_SYMLINKS,
     LINK_WITH_KW,
     LINK_WHOLE_KW,
     CT_INSTALL_TAG_KW,
@@ -2238,6 +2239,7 @@ class Interpreter(InterpreterBase, HoldableObject):
         KwargInfo('subdir', (str, NoneType)),
         INSTALL_MODE_KW.evolve(since='0.47.0'),
         INSTALL_DIR_KW,
+        INSTALL_FOLLOW_SYMLINKS,
     )
     def func_install_headers(self, node: mparser.BaseNode,
                              args: T.Tuple[T.List['mesonlib.FileOrString']],
@@ -2264,7 +2266,8 @@ class Interpreter(InterpreterBase, HoldableObject):
 
         for childdir in dirs:
             h = build.Headers(dirs[childdir], os.path.join(install_subdir, childdir), kwargs['install_dir'],
-                              install_mode, self.subproject)
+                              install_mode, self.subproject,
+                              follow_symlinks=kwargs['follow_symlinks'])
             ret_headers.append(h)
             self.build.headers.append(h)
 
@@ -2459,6 +2462,7 @@ class Interpreter(InterpreterBase, HoldableObject):
         INSTALL_TAG_KW.evolve(since='0.60.0'),
         INSTALL_DIR_KW,
         PRESERVE_PATH_KW.evolve(since='0.64.0'),
+        INSTALL_FOLLOW_SYMLINKS,
     )
     def func_install_data(self, node: mparser.BaseNode,
                           args: T.Tuple[T.List['mesonlib.FileOrString']],
@@ -2486,15 +2490,16 @@ class Interpreter(InterpreterBase, HoldableObject):
 
         install_mode = self._warn_kwarg_install_mode_sticky(kwargs['install_mode'])
         return self.install_data_impl(sources, install_dir, install_mode, rename, kwargs['install_tag'],
-                                      preserve_path=kwargs['preserve_path'])
+                                      preserve_path=kwargs['preserve_path'],
+                                      follow_symlinks=kwargs['follow_symlinks'])
 
     def install_data_impl(self, sources: T.List[mesonlib.File], install_dir: str,
                           install_mode: FileMode, rename: T.Optional[str],
                           tag: T.Optional[str],
                           install_data_type: T.Optional[str] = None,
-                          preserve_path: bool = False) -> build.Data:
+                          preserve_path: bool = False,
+                          follow_symlinks: T.Optional[bool] = None) -> build.Data:
         install_dir_name = install_dir.optname if isinstance(install_dir, P_OBJ.OptionString) else install_dir
-
         dirs = collections.defaultdict(list)
         if preserve_path:
             for file in sources:
@@ -2506,7 +2511,8 @@ class Interpreter(InterpreterBase, HoldableObject):
         ret_data = []
         for childdir, files in dirs.items():
             d = build.Data(files, os.path.join(install_dir, childdir), os.path.join(install_dir_name, childdir),
-                           install_mode, self.subproject, rename, tag, install_data_type)
+                           install_mode, self.subproject, rename, tag, install_data_type,
+                           follow_symlinks)
             ret_data.append(d)
 
         self.build.data.extend(ret_data)
@@ -2525,6 +2531,7 @@ class Interpreter(InterpreterBase, HoldableObject):
                   validator=lambda x: 'cannot be absolute' if any(os.path.isabs(d) for d in x) else None),
         INSTALL_MODE_KW.evolve(since='0.38.0'),
         INSTALL_TAG_KW.evolve(since='0.60.0'),
+        INSTALL_FOLLOW_SYMLINKS,
     )
     def func_install_subdir(self, node: mparser.BaseNode, args: T.Tuple[str],
                             kwargs: 'kwtypes.FuncInstallSubdir') -> build.InstallDir:
@@ -2550,7 +2557,8 @@ class Interpreter(InterpreterBase, HoldableObject):
             exclude,
             kwargs['strip_directory'],
             self.subproject,
-            install_tag=kwargs['install_tag'])
+            install_tag=kwargs['install_tag'],
+            follow_symlinks=kwargs['follow_symlinks'])
         self.build.install_dirs.append(idir)
         return idir
 

mesonbuild/interpreter/kwargs.py

@@ -124,6 +124,7 @@ class FuncInstallSubdir(TypedDict):
     exclude_files: T.List[str]
     exclude_directories: T.List[str]
     install_mode: FileMode
+    follow_symlinks: T.Optional[bool]
 
 
 class FuncInstallData(TypedDict):
@@ -132,6 +133,7 @@ class FuncInstallData(TypedDict):
     sources: T.List[FileOrString]
     rename: T.List[str]
     install_mode: FileMode
+    follow_symlinks: T.Optional[bool]
 
 
 class FuncInstallHeaders(TypedDict):
@@ -139,6 +141,7 @@ class FuncInstallHeaders(TypedDict):
     install_dir: T.Optional[str]
     install_mode: FileMode
     subdir: T.Optional[str]
+    follow_symlinks: T.Optional[bool]
 
 
 class FuncInstallMan(TypedDict):

mesonbuild/interpreter/type_checking.py

@@ -368,6 +368,12 @@ CT_INSTALL_TAG_KW: KwargInfo[T.List[T.Union[str, bool]]] = KwargInfo(
 
 INSTALL_TAG_KW: KwargInfo[T.Optional[str]] = KwargInfo('install_tag', (str, NoneType))
 
+INSTALL_FOLLOW_SYMLINKS: KwargInfo[T.Optional[bool]] = KwargInfo(
+    'follow_symlinks',
+    (bool, NoneType),
+    since='1.3.0',
+)
+
 INSTALL_KW = KwargInfo('install', bool, default=False)
 
 CT_INSTALL_DIR_KW: KwargInfo[T.List[T.Union[str, Literal[False]]]] = KwargInfo(

mesonbuild/minstall.py

@@ -64,9 +64,11 @@ if T.TYPE_CHECKING:
         strip: bool
 
 
-symlink_warning = '''Warning: trying to copy a symlink that points to a file. This will copy the file,
-but this will be changed in a future version of Meson to copy the symlink as is. Please update your
-build definitions so that it will not break when the change happens.'''
+symlink_warning = '''\
+Warning: trying to copy a symlink that points to a file. This currently copies
+the file by default, but will be changed in a future version of Meson to copy
+the link instead.  Set follow_symlinks to true to preserve current behavior, or
+false to copy the link.'''
 
 selinux_updates: T.List[str] = []
 
@@ -389,7 +391,8 @@ class Installer:
         return from_time <= to_time
 
     def do_copyfile(self, from_file: str, to_file: str,
-                    makedirs: T.Optional[T.Tuple[T.Any, str]] = None) -> bool:
+                    makedirs: T.Optional[T.Tuple[T.Any, str]] = None,
+                    follow_symlinks: T.Optional[bool] = None) -> bool:
         outdir = os.path.split(to_file)[0]
         if not os.path.isfile(from_file) and not os.path.islink(from_file):
             raise MesonException(f'Tried to install something that isn\'t a file: {from_file!r}')
@@ -417,10 +420,10 @@ class Installer:
                 # Dangling symlink. Replicate as is.
                 self.copy(from_file, outdir, follow_symlinks=False)
             else:
-                # Remove this entire branch when changing the behaviour to duplicate
-                # symlinks rather than copying what they point to.
-                print(symlink_warning)
-                self.copy2(from_file, to_file)
+                if follow_symlinks is None:
+                    follow_symlinks = True  # TODO: change to False when removing the warning
+                    print(symlink_warning)
+                self.copy2(from_file, to_file, follow_symlinks=follow_symlinks)
         else:
             self.copy2(from_file, to_file)
         selinux_updates.append(to_file)
@@ -454,7 +457,7 @@ class Installer:
 
     def do_copydir(self, data: InstallData, src_dir: str, dst_dir: str,
                    exclude: T.Optional[T.Tuple[T.Set[str], T.Set[str]]],
-                   install_mode: 'FileMode', dm: DirMaker) -> None:
+                   install_mode: 'FileMode', dm: DirMaker, follow_symlinks: T.Optional[bool] = None) -> None:
         '''
         Copies the contents of directory @src_dir into @dst_dir.
 
@@ -519,7 +522,7 @@ class Installer:
                     dm.makedirs(parent_dir)
                     self.copystat(os.path.dirname(abs_src), parent_dir)
                 # FIXME: what about symlinks?
-                self.do_copyfile(abs_src, abs_dst)
+                self.do_copyfile(abs_src, abs_dst, follow_symlinks=follow_symlinks)
                 self.set_mode(abs_dst, install_mode, data.install_umask)
 
     def do_install(self, datafilename: str) -> None:
@@ -613,7 +616,8 @@ class Installer:
             full_dst_dir = get_destdir_path(destdir, fullprefix, i.install_path)
             self.log(f'Installing subdir {i.path} to {full_dst_dir}')
             dm.makedirs(full_dst_dir, exist_ok=True)
-            self.do_copydir(d, i.path, full_dst_dir, i.exclude, i.install_mode, dm)
+            self.do_copydir(d, i.path, full_dst_dir, i.exclude, i.install_mode, dm,
+                            follow_symlinks=i.follow_symlinks)
 
     def install_data(self, d: InstallData, dm: DirMaker, destdir: str, fullprefix: str) -> None:
         for i in d.data:
@@ -622,7 +626,7 @@ class Installer:
             fullfilename = i.path
             outfilename = get_destdir_path(destdir, fullprefix, i.install_path)
             outdir = os.path.dirname(outfilename)
-            if self.do_copyfile(fullfilename, outfilename, makedirs=(dm, outdir)):
+            if self.do_copyfile(fullfilename, outfilename, makedirs=(dm, outdir), follow_symlinks=i.follow_symlinks):
                 self.did_install_something = True
             self.set_mode(outfilename, i.install_mode, d.install_umask)
 
@@ -668,7 +672,8 @@ class Installer:
             fname = os.path.basename(fullfilename)
             outdir = get_destdir_path(destdir, fullprefix, t.install_path)
             outfilename = os.path.join(outdir, fname)
-            if self.do_copyfile(fullfilename, outfilename, makedirs=(dm, outdir)):
+            if self.do_copyfile(fullfilename, outfilename, makedirs=(dm, outdir),
+                                follow_symlinks=t.follow_symlinks):
                 self.did_install_something = True
             self.set_mode(outfilename, t.install_mode, d.install_umask)
 

test cases/common/266 install functions and follow_symlinks/foo/file1

@@ -0,0 +1 @@
+test

test cases/common/266 install functions and follow_symlinks/foo/link1

@@ -0,0 +1 @@
+file1

test cases/common/266 install functions and follow_symlinks/foo/link2.h

@@ -0,0 +1 @@
+file1

test cases/common/266 install functions and follow_symlinks/meson.build

@@ -0,0 +1,38 @@
+project('install_data following symlinks')
+
+install_data(
+  'foo/link1',
+  install_dir: get_option('datadir') / 'followed',
+  follow_symlinks: true,
+)
+
+install_headers(
+  'foo/link2.h',
+  follow_symlinks: true,
+  subdir: 'followed'
+)
+
+install_data(
+  'foo/link1',
+  install_dir: get_option('datadir'),
+  follow_symlinks: false,
+)
+
+install_headers(
+  'foo/link2.h',
+  follow_symlinks: false,
+)
+
+install_subdir(
+  'foo',
+  install_dir: get_option('datadir') / 'subdir',
+  strip_directory: true,
+  follow_symlinks: false,
+)
+
+install_subdir(
+  'foo',
+  install_dir: get_option('datadir') / 'subdir_followed',
+  strip_directory: true,
+  follow_symlinks: true,
+)

test cases/common/266 install functions and follow_symlinks/test.json

@@ -0,0 +1,14 @@
+{
+  "installed": [
+    {"type": "link", "file": "usr/share/link1"},
+    {"type": "link", "file": "usr/include/link2.h"},
+    {"type": "file", "file": "usr/share/followed/link1"},
+    {"type": "file", "file": "usr/include/followed/link2.h"},
+    {"type": "link", "file": "usr/share/subdir/link1"},
+    {"type": "link", "file": "usr/share/subdir/link2.h"},
+    {"type": "file", "file": "usr/share/subdir/file1"},
+    {"type": "file", "file": "usr/share/subdir_followed/link1"},
+    {"type": "file", "file": "usr/share/subdir_followed/link2.h"},
+    {"type": "file", "file": "usr/share/subdir_followed/file1"}
+  ]
+}