install_{data,headers,subdir}: implement follow_symlinks

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

1 files changed, 18 insertions, 13 deletions

diff --git a/mesonbuild/minstall.py b/mesonbuild/minstall.py
index 0d397b2..5f8629b 100644
--- a/mesonbuild/minstall.py
+++ b/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)