Immutable Extracts

internal/project/project_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"reflect"
 	"slices"
 	"strings"
 	"testing"
@@ -254,6 +255,15 @@ extract:
   layout: nwn_canonical_json
   hak_discovery: configured_haks
   cleanup_stale: false
+  merge:
+    gff_json:
+      - target: module/module.ifo.json
+        preserve_fields:
+          - Mod_Entry_Area
+        merge_lists:
+          - field: Mod_Area_list
+            key_field: Area_Name
+            strategy: preserve_existing_order_append_new
 topdata:
   wiki:
     source: topdata/wiki
@@ -305,6 +315,19 @@ autogen:
 	if effective.Extract.CleanupStale == nil || *effective.Extract.CleanupStale {
 		t.Fatalf("expected cleanup_stale false, got %#v", effective.Extract.CleanupStale)
 	}
+	if got, want := len(effective.Extract.Merge.GFFJSON), 1; got != want {
+		t.Fatalf("expected %d gff json merge rule, got %d", want, got)
+	}
+	rule := effective.Extract.Merge.GFFJSON[0]
+	if got, want := rule.Target, "module/module.ifo.json"; got != want {
+		t.Fatalf("expected merge target %q, got %q", want, got)
+	}
+	if got, want := rule.PreserveFields, []string{"Mod_Entry_Area"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("expected preserve fields %#v, got %#v", want, got)
+	}
+	if got, want := rule.MergeLists[0].Strategy, "preserve_existing_order_append_new"; got != want {
+		t.Fatalf("expected merge list strategy %q, got %q", want, got)
+	}
 	if got, want := effective.TopData.Wiki.DeployManifest, "wiki-manifest.json"; got != want {
 		t.Fatalf("expected wiki deploy manifest %q, got %q", want, got)
 	}
@@ -346,6 +369,91 @@ autogen:
 	}
 }
 
+func TestValidateLayoutRejectsInvalidExtractMergeRules(t *testing.T) {
+	tests := []struct {
+		name    string
+		config  string
+		wantErr string
+	}{
+		{
+			name: "empty target",
+			config: `
+extract:
+  merge:
+    gff_json:
+      - target: ""
+        preserve_fields: [Mod_Entry_Area]
+`,
+			wantErr: "extract.merge.gff_json[0].target must not be empty",
+		},
+		{
+			name: "duplicate target",
+			config: `
+extract:
+  merge:
+    gff_json:
+      - target: module/module.ifo.json
+      - target: module/module.ifo.json
+`,
+			wantErr: "extract.merge.gff_json target \"module/module.ifo.json\" is configured more than once",
+		},
+		{
+			name: "empty merge list field",
+			config: `
+extract:
+  merge:
+    gff_json:
+      - target: module/module.ifo.json
+        merge_lists:
+          - field: ""
+            key_field: Area_Name
+            strategy: preserve_existing_order_append_new
+`,
+			wantErr: "extract.merge.gff_json[0].merge_lists[0].field must not be empty",
+		},
+		{
+			name: "unsupported strategy",
+			config: `
+extract:
+  merge:
+    gff_json:
+      - target: module/module.ifo.json
+        merge_lists:
+          - field: Mod_Area_list
+            key_field: Area_Name
+            strategy: replace
+`,
+			wantErr: "extract.merge.gff_json[0].merge_lists[0].strategy \"replace\" is not supported",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			root := t.TempDir()
+			writeProjectFile(t, filepath.Join(root, ConfigFile), `
+module:
+  name: Test Module
+  resref: testmod
+paths:
+  source: src
+  build: build
+`+tt.config)
+
+			proj, err := Load(root)
+			if err != nil {
+				t.Fatalf("Load returned error: %v", err)
+			}
+			err = proj.ValidateLayout()
+			if err == nil {
+				t.Fatalf("expected validation error containing %q", tt.wantErr)
+			}
+			if !strings.Contains(err.Error(), tt.wantErr) {
+				t.Fatalf("expected validation error containing %q, got %v", tt.wantErr, err)
+			}
+		})
+	}
+}
+
 func TestActiveOverridesAreVisibleAndSensitiveValuesAreMasked(t *testing.T) {
 	root := t.TempDir()
 	writeProjectFile(t, filepath.Join(root, ConfigFile), `