Introduce preset dependencies

Instead of building presets in alphanumerical order, let's introduce
a proper concept of dependencies. Dependencies are configured with
the new "Dependencies=" option in the new "[Preset]" section. All
presets configured with "Dependencies=" are built before the current
preset.

We drop the alphanumerical preset in favor of explicit dependencies.

diff --git a/mkosi.md b/mkosi.md
index 39ba9163d70400421194c5e53c205f5bb5c7c537..1ebe4ed59581eed7a1b6950f2d2c831b7e4daca1 100644 (file)
--- a/mkosi.md
+++ b/mkosi.md
@@ -190,9 +190,10 @@ Those settings cannot be configured in the configuration files.
 
 `--preset=`
 
-: If specified, only build the given preset. Can be specified multiple
-  times to build multiple presets. If not specified, all presets are
-  built. See the `Presets` section for more information.
+: If specified, only build the given presets. Can be specified multiple
+  times to build multiple presets. All the given presets and their
+  dependencies are built. If not specified, all presets are built. See
+  the `Presets` section for more information.
 
 ## Supported output formats
 
@@ -300,6 +301,15 @@ they should be specified with a boolean argument: either "1", "yes", or "true" t
 | `ImageVersion=` | no    | yes              | match fails             |
 | `Bootable=`     | no    | no               | match auto feature      |
 
+### [Preset] Section
+
+`Dependencies=`, `--dependency=`
+
+: The presets that this preset depends on specified as a comma-separated
+  list. All presets configured in this option will be built before this
+  preset and will be pulled in as dependencies of this preset when
+  `--preset` is used.
+
 ### [Distribution] Section
 
 `Distribution=`, `--distribution=`, `-d`
@@ -1337,22 +1347,18 @@ directories containing mkosi configuration files or regular files with
 the `.conf` extension.
 
 When presets are found in `mkosi.presets/`, mkosi will build the
-configured presets (or all of them if none were explicitly configured
-using `--preset=`) in alphanumerical order. To enforce a certain build
-order, preset names can be numerically prefixed (e.g. `00-initrd.conf`).
-The numerical prefix will be removed from the preset name during parsing,
-along with the `.conf` suffix (`00-initrd.conf` becomes `initrd`). The
-preset name is used for display purposes and also as the default output
-name if none is explicitly configured.
+configured preset and its dependencies (or all of them if no presets
+were explicitly configured using `--preset=`). To add dependencies
+between presets, the `Dependencies=` setting can be used.
 
 When presets are defined, mkosi will first read the global configuration
 (configuration outside of the `mkosi.presets/` directory), followed by
 the preset specific configuration. This means that global configuration
 takes precedence over preset specific configuration.
 
-Later presets can refer to outputs of earlier presets. Specifically, for
-the following options, mkosi will only check whether the inputs exist
-just before building the preset:
+Presets can refer to outputs of presets they depend on. Specifically,
+for the following options, mkosi will only check whether the inputs
+exist just before building the preset:
 
 - `BaseTrees=`
 - `PackageManagerTrees=`
@@ -1361,9 +1367,9 @@ just before building the preset:
 - `ToolsTree=`
 - `Initrds=`
 
-To refer to outputs of earlier presets, simply configure any of these
-options with a relative path to the location of the output to use in the
-earlier preset's output directory.
+To refer to outputs of a preset's dependencies, simply configure any of
+these options with a relative path to the output to use in the output
+directory of the dependency.
 
 A good example on how to use presets can be found in the systemd
 repository: https://github.com/systemd/systemd/tree/main/mkosi.presets.

diff --git a/mkosi/config.py b/mkosi/config.py
index 808f97ee0cd2a330ec2b183fd7964b079731c799..50de80fec0627cecf5fccb2931e53984cfa0d089 100644 (file)
--- a/mkosi/config.py
+++ b/mkosi/config.py
@@ -8,13 +8,13 @@ import dataclasses
 import enum
 import fnmatch
 import functools
+import graphlib
 import inspect
 import operator
 import os.path
 import platform
 import shlex
 import shutil
-import string
 import subprocess
 import sys
 import textwrap
@@ -628,6 +628,7 @@ class MkosiConfig:
     access the value from state.
     """
 
+    dependencies: tuple[str]
     distribution: Distribution
     release: str
     mirror: Optional[str]
@@ -798,6 +799,13 @@ class MkosiConfig:
 
 class MkosiConfigParser:
     SETTINGS = (
+        MkosiConfigSetting(
+            dest="dependencies",
+            long="--dependency",
+            section="Preset",
+            parse=config_make_list_parser(delimiter=","),
+            help="Specify other presets that this preset depends on",
+        ),
         MkosiConfigSetting(
             dest="distribution",
             short="-d",
@@ -1703,8 +1711,9 @@ class MkosiConfigParser:
             "--preset",
             action="append",
             dest="presets",
+            metavar="PRESET",
             default=[],
-            help="Build the specified preset",
+            help="Build the specified presets and their dependencies",
         )
         parser.add_argument(
             "--nspawn-keep-unit",
@@ -1767,6 +1776,32 @@ class MkosiConfigParser:
             delattr(namespace, "cache")
             print("Warning: --cache is no longer supported")
 
+    def resolve_deps(self, args: MkosiArgs, presets: Sequence[MkosiConfig]) -> list[MkosiConfig]:
+        graph = {p.preset: p.dependencies for p in presets}
+
+        if args.presets:
+            if any((missing := p) not in graph for p in args.presets):
+                die(f"No preset found with name {missing}")
+
+            deps = set()
+            queue = [*args.presets]
+
+            while queue:
+                if (preset := queue.pop(0)) not in deps:
+                    deps.add(preset)
+                    queue.extend(graph[preset])
+
+            presets = [p for p in presets if p.preset in deps]
+
+        graph = {p.preset: p.dependencies for p in presets}
+
+        try:
+            order = list(graphlib.TopologicalSorter(graph).static_order())
+        except graphlib.CycleError as e:
+            die(f"Preset dependency cycle detected: {' => '.join(e.args[1])}")
+
+        return sorted(presets, key=lambda p: order.index(p.preset))
+
     def parse(self, argv: Optional[Sequence[str]] = None) -> tuple[MkosiArgs, tuple[MkosiConfig, ...]]:
         presets = []
         namespace = argparse.Namespace()
@@ -1808,15 +1843,13 @@ class MkosiConfigParser:
             self.parse_config(Path("."), namespace)
 
             if Path("mkosi.presets").exists():
-                for p in sorted(Path("mkosi.presets").iterdir()):
+                for p in Path("mkosi.presets").iterdir():
                     if not p.is_dir() and not p.suffix == ".conf":
                         continue
 
-                    name = p.name.lstrip(string.digits + "-").removesuffix(".conf")
+                    name = p.name.removesuffix(".conf")
                     if not name:
                         die(f"{p} is not a valid preset name")
-                    if args.presets and name not in args.presets:
-                        continue
 
                     cp = copy.deepcopy(namespace)
 
@@ -1853,7 +1886,10 @@ class MkosiConfigParser:
         # infrastructure scripts rather than image-specific configuration.
         self.backward_compat_stubs(namespace)
 
-        return args, tuple(load_config(ns) for ns in presets)
+        presets = [load_config(ns) for ns in presets]
+        presets = self.resolve_deps(args, presets)
+
+        return args, tuple(presets)
 
 
 def load_credentials(args: argparse.Namespace) -> dict[str, str]:
@@ -2090,6 +2126,9 @@ def summary(args: MkosiArgs, config: MkosiConfig) -> str:
                           Verb: {bold(args.verb)}
                        Cmdline: {bold(" ".join(args.cmdline))}
 
+    {bold("PRESET")}:
+                  Dependencies: {line_join_list(config.dependencies)}
+
     {bold("DISTRIBUTION")}:
                   Distribution: {bold(config.distribution)}
                        Release: {bold(none_to_na(config.release))}