Add some very basic cache invalidation

Let's compare the packages, build packages, repositories and the
contents of the prepare script. This doesn't cover everything but
should be sufficient to catch most changes without having to run
with "-ff".

diff --git a/mkosi/__init__.py b/mkosi/__init__.py
index 16c2b9abceebe57269f2d9e8d90a2316c4bbef70..643da964b9a49a94b058e2fa2bff96601ad79d0c 100644 (file)
--- a/mkosi/__init__.py
+++ b/mkosi/__init__.py
@@ -1032,7 +1032,7 @@ def unlink_output(args: MkosiArgs, config: MkosiConfig) -> None:
     if remove_build_cache:
         for p in cache_tree_paths(config):
             if p.exists():
-                with complete_step(f"Removing cache directory {p}…"):
+                with complete_step(f"Removing cache entry {p}…"):
                     unlink_try_hard(p)
 
         if config.build_dir and config.build_dir.exists() and any(config.build_dir.iterdir()):
@@ -1049,9 +1049,13 @@ def unlink_output(args: MkosiArgs, config: MkosiConfig) -> None:
                 empty_directory(config.cache_dir)
 
 
-def cache_tree_paths(config: MkosiConfig) -> tuple[Path, Path]:
+def cache_tree_paths(config: MkosiConfig) -> tuple[Path, Path, Path]:
     assert config.cache_dir
-    return config.cache_dir / f"{config.output}.cache", config.cache_dir / f"{config.output}.build.cache"
+    return (
+        config.cache_dir / f"{config.output}.cache",
+        config.cache_dir / f"{config.output}.build.cache",
+        config.cache_dir / f"{config.output}.manifest",
+    )
 
 
 def check_tree_input(path: Optional[Path]) -> None:
@@ -1456,7 +1460,7 @@ def save_cache(state: MkosiState) -> None:
     if not state.config.incremental:
         return
 
-    final, build = cache_tree_paths(state.config)
+    final, build, manifest = cache_tree_paths(state.config)
 
     with complete_step("Installing cache copies"):
         unlink_try_hard(final)
@@ -1472,15 +1476,22 @@ def save_cache(state: MkosiState) -> None:
             unlink_try_hard(build)
             shutil.move(state.workspace / "build-overlay", build)
 
+        manifest.write_text(json.dumps(state.config.cache_manifest()))
+
 
 def reuse_cache(state: MkosiState) -> bool:
     if not state.config.incremental:
         return False
 
-    final, build = cache_tree_paths(state.config)
+    final, build, manifest = cache_tree_paths(state.config)
     if not final.exists() or (state.config.build_script and not build.exists()):
         return False
 
+    if manifest.exists():
+        prev = json.loads(manifest.read_text())
+        if prev != state.config.cache_manifest():
+            return False
+
     with complete_step("Copying cached trees"):
         btrfs_maybe_snapshot_subvolume(state.config, final, state.root)
         if state.config.build_script:

diff --git a/mkosi/config.py b/mkosi/config.py
index 55220ec877b9374b3c23ed4955c416d36a58a645..ebd4871ce567273370c08a08ea60c3906143cdec 100644 (file)
--- a/mkosi/config.py
+++ b/mkosi/config.py
@@ -1,4 +1,5 @@
 import argparse
+import base64
 import configparser
 import copy
 import dataclasses
@@ -716,6 +717,18 @@ class MkosiConfig:
     def output_changelog(self) -> str:
         return f"{self.output_with_version}.changelog"
 
+    def cache_manifest(self) -> dict[str, Any]:
+        manifest: dict[str, Any] = {
+            "packages": self.packages,
+            "build_packages": self.build_packages,
+            "repositories": self.repositories,
+        }
+
+        if self.prepare_script:
+            manifest["prepare_script"] = base64.b64encode(self.prepare_script.read_bytes()).decode()
+
+        return manifest
+
 
 class MkosiConfigParser:
     SETTINGS = (