fix: deref legacy symlinks (#127)

* fix: deref legacy syms before deploy

Deploy will completely overwrite symlinked dirs, so you'd lose all extra
content inside them
Also deref syms in config backup before deleting legacy dir

* fix: restore link if deref fails

src/caelestia/subcommands/install.py

@@ -4,7 +4,13 @@ from argparse import Namespace
 from pathlib import Path
 
 from caelestia.utils.dots.deployer import Deployer
-from caelestia.utils.dots.legacy import LEGACY_META_PKG, detect_legacy_repo, legacy_to_delete
+from caelestia.utils.dots.legacy import (
+    LEGACY_META_PKG,
+    detect_legacy_repo,
+    legacy_config_symlinks,
+    legacy_symlinks,
+    legacy_to_delete,
+)
 from caelestia.utils.dots.manifest import ComponentError, Manifest, ManifestError
 from caelestia.utils.dots.misc import build_local_packages, run_hooks
 from caelestia.utils.dots.packages import DEFAULT_AUR_HELPER, PackageError, PackageInstaller
@@ -23,6 +29,21 @@ def _parse_list_arg(value: str | None) -> list[str] | None:
     return [item.strip() for item in value.split(",") if item.strip()]
 
 
+def _deref_symlink(link: Path, target: Path) -> None:
+    """Replace symlink `link` with a real copy of `target`'s content."""
+
+    bak = link.rename(link.parent / f"{link.name}.bak")
+    try:
+        if target.is_dir():
+            shutil.copytree(target, link, symlinks=True)
+        else:
+            shutil.copy2(target, link)
+    except OSError:
+        bak.rename(link)
+        raise
+    bak.unlink()
+
+
 class Command:
     args: Namespace
 
@@ -43,6 +64,7 @@ class Command:
         except PackageError as e:
             fatal(e)
         run_hooks(manifest, "post_package")
+        self.dereference_legacy(legacy_dir)  # Copy legacy content into place before deploy overwrites the symlinks
         deployed = self.deploy_configs(source, manifest)
         run_hooks(manifest, "post_install")
 
@@ -171,6 +193,42 @@ class Command:
 
         return installer, packages, local_packages
 
+    def dereference_legacy(self, legacy_dir: Path | None) -> None:
+        """Replace legacy symlinks with real copies of their targets."""
+
+        symlinks = legacy_symlinks(legacy_dir)
+        if not symlinks:
+            return
+
+        print()
+        log("Preserving content from legacy symlinks...")
+        for path in symlinks:
+            target = path.resolve()
+            if not target.exists():
+                continue
+
+            try:
+                _deref_symlink(path, target)
+                info(f"Copied {target} -> {path}")
+            except OSError as e:
+                warn(f"failed to preserve {path}: {e}")
+
+    def deref_backup_syms(self, legacy_dir: Path | None) -> None:
+        """Deref the backup's legacy symlinks before the repo is cleared, so the backup keeps real content."""
+
+        if not config_backup_dir.is_dir():
+            return
+
+        for link in legacy_config_symlinks(config_backup_dir, legacy_dir):
+            target = link.resolve()
+            if not target.exists():
+                continue
+
+            try:
+                _deref_symlink(link, target)
+            except OSError as e:
+                warn(f"failed to preserve {link} in backup: {e}")
+
     def migrate_legacy(self, installer: PackageInstaller, legacy_dir: Path | None) -> None:
         """Clean up a previous install.fish setup (repo, symlinks and metapackage)."""
 
@@ -186,6 +244,7 @@ class Command:
 
         deployer = Deployer()
         try:
+            self.deref_backup_syms(legacy_dir)
             for path in to_delete:
                 deployer.remove(path)
                 info(f"Deleted {path}")

src/caelestia/utils/dots/legacy.py

@@ -46,6 +46,10 @@ def _find_legacy_repo(path: Path) -> Path | None:
         return path
 
 
+def _filter_candidates(candidates: list[Path], legacy_dir: Path) -> list[Path]:
+    return [path for path in candidates if path.is_symlink() and legacy_dir in path.resolve().parents]
+
+
 def detect_legacy_repo() -> Path | None:
     for conf in _confs:
         path = config_dir / conf
@@ -59,25 +63,32 @@ def detect_legacy_repo() -> Path | None:
     return _find_legacy_repo(data_dir / "caelestia")
 
 
+def legacy_config_symlinks(base: Path, legacy_dir: Path | None) -> list[Path]:
+    """Config-relative links install.fish created, resolved under `base` (the live config or a backup of it)."""
+
+    if not legacy_dir:
+        return []
+
+    candidates = [base / conf for conf in _confs]
+    return _filter_candidates(candidates, legacy_dir)
+
+
+def legacy_symlinks(legacy_dir: Path | None) -> list[Path]:
+    """All paths symlinked into the legacy repo (the links install.fish created)."""
+
+    if not legacy_dir:
+        return []
+
+    extras = [
+        *(Path.home() / ".zen").glob("*/chrome/userChrome.css"),
+        Path.home() / ".local/lib/caelestia/caelestiafox",
+    ]
+
+    return [*legacy_config_symlinks(config_dir, legacy_dir), *_filter_candidates(extras, legacy_dir)]
+
+
 def legacy_to_delete(legacy_dir: Path | None) -> list[Path]:
     if not legacy_dir:
         return []
 
-    to_delete = []
-
-    for conf in _confs:
-        path = config_dir / conf
-        if path.is_symlink() and legacy_dir in path.resolve().parents:
-            to_delete.append(path)
-
-    others = [
-        *(Path.home() / ".zen").glob("*/chrome/userChrome.css"),
-        Path.home() / ".local/lib/caelestia/caelestiafox",
-    ]
-    for path in others:
-        if path.is_symlink() and legacy_dir in path.resolve().parents:
-            to_delete.append(path)
-
-    to_delete.append(legacy_dir)
-
-    return to_delete
+    return [*legacy_symlinks(legacy_dir), legacy_dir]