osinfo: read blueprints from variants

doc/20-advanced/20-bootc/05-sources-of-configuration.md

@@ -275,9 +275,48 @@ partition_table:
 > [!WARNING]
 > *LUKS configurations currently do not work with bootable containers in `image-builder`. See [here](https://github.com/osbuild/images/issues/2228).*
 
+### `blueprint.json` / `blueprint.toml`
+
+A JSON or TOML file containing blueprint customizations to apply when building an image from the container. The canonical location is `/usr/lib/image-builder/bootc/blueprint.json` (or `blueprint.toml`). Only the `customizations` section of the blueprint is used; fields like `packages` do not apply to bootc images since the package set comes from the container itself.
+
+This allows containers to ship default customizations (users, kernel arguments, services, firewall rules, etc.) so that images built from the container are configured correctly without requiring the end-user to supply a separate blueprint.
+
+Example `blueprint.json`:
+
+```json
+{
+  "customizations": {
+    "user": [
+      {
+        "name": "admin",
+        "groups": ["wheel"]
+      }
+    ],
+    "kernel": {
+      "append": "quiet"
+    }
+  }
+}
+```
+
+Equivalent `blueprint.toml`:
+
+```toml
+[[customizations.user]]
+name = "admin"
+groups = ["wheel"]
+
+[customizations.kernel]
+append = "quiet"
+```
+
+For backward compatibility, `config.json` and `config.toml` are also recognized at the same locations. The `blueprint.*` filenames take precedence when both exist.
+
+Like `disk.yaml`, these files support [deployment variant](#deployment-variants) overrides.
+
 ### Deployment Variants
 
-Containers can ship multiple `disk.yaml`, `iso.yaml`, and/or `extras.yaml` configurations as *deployment variants*. Variants allow a single container image to produce different disk layouts depending on the target environment, for example a `secure-execution` variant with verity partitions for s390x, or `btrfs` vs `ext4` variants for Fedora images.
+Containers can ship multiple `disk.yaml`, `iso.yaml`, `extras.yaml`, and/or `blueprint.json`/`blueprint.toml` configurations as *deployment variants*. Variants allow a single container image to produce different configurations depending on the target environment, for example a `secure-execution` variant with verity partitions for s390x, or `btrfs` vs `ext4` variants for Fedora images.
 
 Variants are placed in the `variant.d/` subdirectory, with each variant in its own named directory:
 
@@ -286,15 +325,17 @@ Variants are placed in the `variant.d/` subdirectory, with each variant in its o
 ├── disk.yaml              # default configuration
 ├── iso.yaml               # default ISO configuration
 ├── extras.yaml            # default extras configuration
+├── blueprint.json         # default blueprint customizations
 └── variant.d/
     ├── btrfs/
     │   ├── disk.yaml      # btrfs partition layout
     │   └── extras.yaml    # btrfs-specific extras
     └── secure-execution/
-        └── disk.yaml      # s390x SE partition layout
+        ├── disk.yaml      # s390x SE partition layout
+        └── blueprint.json # s390x SE customizations
 ```
 
-Each variant directory may contain a `disk.yaml`, `iso.yaml`, and/or `extras.yaml`. When a variant is selected at build time with `--bootc-variant`, `image-builder` uses the variant's configuration files. For any file not provided by the variant, `image-builder` falls back to the default configuration.
+Each variant directory may contain a `disk.yaml`, `iso.yaml`, `extras.yaml`, and/or `blueprint.json`/`blueprint.toml`. When a variant is selected at build time with `--bootc-variant`, `image-builder` uses the variant's configuration files. For any file not provided by the variant, `image-builder` falls back to the default configuration.
 
 Users can list available variants and select one at build time:
 

pkg/bib/osinfo/osinfo.go

@@ -192,28 +192,29 @@ func readSelinuxPolicy(fsys fs.FS) (string, error) {
 	return policy, nil
 }
 
-func readImageCustomization(fsys fs.FS) (*blueprint.Customizations, error) {
-	// note that we only look at the 'old' search path here, we do want to
-	// look in the new path as well but i'd like to only support the actual
-	// blueprint format there instead of buildconfig as well
-	prefix := searchPaths[1]
-
-	config, err := blueprintload.LoadFS(fsys, path.Join(prefix, "config.json"))
-	if err != nil && !os.IsNotExist(err) {
-		return nil, err
-	}
-	if config == nil {
-		config, err = blueprintload.LoadFS(fsys, path.Join(prefix, "config.toml"))
-		if err != nil && !os.IsNotExist(err) {
-			return nil, err
+func readImageCustomization(fsys fs.FS, prefix, variant string) (*blueprint.Customizations, error) {
+	searchDirs := []string{prefix}
+	if variant != "" {
+		searchDirs = []string{
+			path.Join(prefix, "variant.d", variant),
+			prefix,
 		}
 	}
-	// no config found in either toml/json
-	if config == nil {
-		return nil, nil
+
+	for _, dir := range searchDirs {
+		for _, filename := range []string{"blueprint.json", "blueprint.toml", "config.json", "config.toml"} {
+			config, err := blueprintload.LoadFS(fsys, path.Join(dir, filename))
+			if err != nil {
+				if os.IsNotExist(err) {
+					continue
+				}
+				return nil, err
+			}
+			return config.Customizations, nil
+		}
 	}
 
-	return config.Customizations, nil
+	return nil, nil
 }
 
 type diskYAML struct {
@@ -438,7 +439,7 @@ func Load(fsys fs.FS, variant string) (*Info, error) {
 		return nil, fmt.Errorf("variant %q not found", variant)
 	}
 
-	customization, err := readImageCustomization(fsys)
+	customization, err := readImageCustomization(fsys, prefix, variant)
 	if err != nil {
 		return nil, err
 	}

pkg/bib/osinfo/osinfo_test.go

@@ -57,10 +57,13 @@ func createBootupdEFI(t *testing.T, root, uefiVendor string) {
 	require.NoError(t, err)
 }
 
-func createImageCustomization(t *testing.T, root, custType string) {
+func createImageCustomization(t *testing.T, root, custType string, variant ...string) {
 	t.Helper()
 
 	bibDir := path.Join(root, "usr/lib/bootc-image-builder/")
+	if len(variant) > 0 && variant[0] != "" {
+		bibDir = path.Join(root, "usr/lib/bootc-image-builder/variant.d", variant[0])
+	}
 	err := os.MkdirAll(bibDir, 0755)
 	require.NoError(t, err)
 
@@ -179,6 +182,58 @@ func TestLoadInfo(t *testing.T) {
 	}
 }
 
+var testCustomizationJSON = `{
+	"customizations": {
+		"disk": {
+			"partitions": [
+				{
+					"label": "var",
+					"mountpoint": "/var",
+					"fs_type": "ext4",
+					"minsize": "3 GiB"
+				}
+			]
+		}
+	}
+}`
+
+func TestLoadInfoVariantCustomization(t *testing.T) {
+	root := t.TempDir()
+	writeOSRelease(t, root, "fedora", "40", "Fedora Linux", "platform:f40", "coreos", "")
+	createBootupdEFI(t, root, "fedora")
+
+	variantDir := path.Join(root, "usr/lib/image-builder/bootc/variant.d/myvariant")
+	require.NoError(t, os.MkdirAll(variantDir, 0755))
+	require.NoError(t, os.WriteFile(path.Join(variantDir, "blueprint.json"), []byte(testCustomizationJSON), 0644))
+
+	info, err := Load(os.DirFS(root), "myvariant")
+	require.NoError(t, err)
+	require.NotNil(t, info.ImageCustomization)
+	require.NotNil(t, info.ImageCustomization.Disk)
+	require.NotEmpty(t, info.ImageCustomization.Disk.Partitions)
+	assert.Equal(t, "var", info.ImageCustomization.Disk.Partitions[0].Label)
+}
+
+func TestLoadInfoVariantFallback(t *testing.T) {
+	root := t.TempDir()
+	writeOSRelease(t, root, "fedora", "40", "Fedora Linux", "platform:f40", "coreos", "")
+	createBootupdEFI(t, root, "fedora")
+
+	baseDir := path.Join(root, "usr/lib/image-builder/bootc")
+	require.NoError(t, os.MkdirAll(baseDir, 0755))
+	require.NoError(t, os.WriteFile(path.Join(baseDir, "blueprint.json"), []byte(testCustomizationJSON), 0644))
+
+	variantDir := path.Join(baseDir, "variant.d/myvariant")
+	require.NoError(t, os.MkdirAll(variantDir, 0755))
+
+	info, err := Load(os.DirFS(root), "myvariant")
+	require.NoError(t, err)
+	require.NotNil(t, info.ImageCustomization)
+	require.NotNil(t, info.ImageCustomization.Disk)
+	require.NotEmpty(t, info.ImageCustomization.Disk.Partitions)
+	assert.Equal(t, "var", info.ImageCustomization.Disk.Partitions[0].Label)
+}
+
 func TestLoadInfoKernel(t *testing.T) {
 	type testCase struct {
 		desc     string