Prepare reusable CLI override batches

internal/engine/override_test.go

@@ -446,6 +446,85 @@ func TestOverrideAggregateLimitsFailBeforeApplication(t *testing.T) {
 	}
 }
 
+func TestPreparedOverrideBatchDetachesInputsAndAllocatesSourcesInOrder(t *testing.T) {
+	base, diagnostics := composeDocuments(parseCompositionDocument(t, "base", "settings: {}\n"))
+	if len(diagnostics) != 0 {
+		t.Fatal(diagnostics)
+	}
+	sources := []SourceInfo{{ID: "source-1", Label: "base", Layer: LayerBase, Kind: SourceKindMapping}}
+	firstValue := map[string]any{"nested": map[string]any{"name": "original"}}
+	secondValue := []any{map[string]any{"enabled": true}}
+	batch, diagnostics := prepareOverrides(base, sources, []Override{
+		{Path: Keys("settings", "first"), Value: firstValue, Flag: "--first"},
+		{Path: Keys("settings", "second"), Value: secondValue, Flag: "--second"},
+	}, nil, defaultImportLimits())
+	if len(diagnostics) != 0 {
+		t.Fatalf("prepare overrides: %#v", diagnostics)
+	}
+	if len(batch.overrides) != 2 || len(batch.sources) != 3 {
+		t.Fatalf("prepared counts = %d overrides, %d sources", len(batch.overrides), len(batch.sources))
+	}
+	for index, want := range []string{"source-2", "source-3"} {
+		if batch.overrides[index].source.ID != want || batch.sources[index+1].ID != want {
+			t.Errorf("prepared source %d = %#v / %#v, want %s", index, batch.overrides[index].source, batch.sources[index+1], want)
+		}
+	}
+	if batch.sources[1].Label != "--first" || batch.sources[2].Label != "--second" {
+		t.Fatalf("synthetic source order = %#v", batch.sources)
+	}
+
+	firstValue["nested"].(map[string]any)["name"] = "changed after preparation"
+	preparedName, found := documentAtPath(batch.overrides[0].value, Keys("nested", "name"))
+	if !found || preparedName.Text != "original" {
+		t.Fatalf("prepared override aliases input value: %#v, %v", preparedName, found)
+	}
+	preparedName.Text = "changed prepared snapshot"
+	if firstValue["nested"].(map[string]any)["name"] != "changed after preparation" {
+		t.Fatal("prepared override mutation changed caller input")
+	}
+	batch.sources[0].Label = "changed batch source"
+	if sources[0].Label != "base" {
+		t.Fatal("prepared source list aliases the input source list")
+	}
+	if len(base.root.Mapping) != 1 || base.root.Mapping[0].Value.Kind != document.Mapping || len(base.root.Mapping[0].Value.Mapping) != 0 {
+		t.Fatalf("preparation mutated assembled input: %#v", base.root)
+	}
+}
+
+func TestPostStructuralOverridePreparationRejectsInheritanceDirectives(t *testing.T) {
+	base, diagnostics := composeDocuments(parseCompositionDocument(t, "base", "child: {}\nitems: []\n"))
+	if len(diagnostics) != 0 {
+		t.Fatal(diagnostics)
+	}
+	tests := []struct {
+		name     string
+		override Override
+		path     string
+	}{
+		{
+			name:     "supplied path",
+			override: Override{Path: Keys("child", "extends"), Value: "parent", Flag: "--extends"},
+			path:     "/child/extends",
+		},
+		{
+			name:     "nested value",
+			override: Override{Path: Keys("items"), Value: []any{map[string]any{"extends": "parent"}}, Flag: "--items"},
+			path:     "/items/0/extends",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if _, diagnostics := prepareOverrides(base, nil, []Override{test.override}, nil, defaultImportLimits()); len(diagnostics) != 0 {
+				t.Fatalf("legacy preparation changed before lifecycle activation: %#v", diagnostics)
+			}
+			_, diagnostics := preparePostStructuralOverrides(overridePreparationInputFor(base), nil, []Override{test.override}, nil, defaultImportLimits())
+			if len(diagnostics) != 1 || diagnostics[0].Code != CodeOverrideDirective || diagnostics[0].Path.String() != test.path {
+				t.Fatalf("post-structural diagnostics = %#v, want directive at %s", diagnostics, test.path)
+			}
+		})
+	}
+}
+
 func historyLayers(history []Change) []Layer {
 	layers := make([]Layer, len(history))
 	for index, change := range history {