full json merging

Signed-off-by: awphi <26072111+awphi@users.noreply.github.com>

Author: awphi

internal/testutil/testutil.go

@@ -3,6 +3,7 @@ package testutil
 import (
 	"encoding/json"
 	"fmt"
+	"maps"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -12,6 +13,7 @@ import (
 	"testing"
 
 	"github.com/arm/topo/internal/template"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -110,10 +112,10 @@ func AssertFileContents(t *testing.T, wantContents string, path string) {
 
 func AssertJsonGoldenFile(t *testing.T, got string, goldenPath string) {
 	t.Helper()
-	AssertJsonGoldenFileWithOverrides(t, got, goldenPath, map[string]any{})
+	AssertJsonGoldenFileWithOverrides(t, got, goldenPath, nil)
 }
 
-func AssertJsonGoldenFileWithOverrides(t *testing.T, got string, goldenPath string, overrides map[string]any) {
+func AssertJsonGoldenFileWithOverrides(t *testing.T, got string, goldenPath string, overrides any) {
 	t.Helper()
 
 	if os.Getenv("UPDATE_GOLDEN") == "1" {
@@ -122,37 +124,75 @@ func AssertJsonGoldenFileWithOverrides(t *testing.T, got string, goldenPath stri
 		t.Skipf("Updated golden file: %s", goldenPath)
 	}
 
-	gotObj := make(map[string]any)
-	err := json.Unmarshal([]byte(got), &gotObj)
+	wantBytes, err := os.ReadFile(goldenPath)
 	require.NoError(t, err)
 
-	wantBytes, err := os.ReadFile(goldenPath)
+	var wantValue any
+	err = json.Unmarshal(wantBytes, &wantValue)
 	require.NoError(t, err)
 
-	wantObj := make(map[string]any)
-	err = json.Unmarshal(wantBytes, &wantObj)
+	if hasJSONOverrides(overrides) {
+		wantValue = MergeJSONValues(wantValue, overrides)
+	}
+
+	wantWithOverrides, err := json.Marshal(wantValue)
 	require.NoError(t, err)
 
-	deepMergeMaps(wantObj, overrides)
+	assert.JSONEq(t, string(wantWithOverrides), got, "output did not match golden file %s", goldenPath)
+}
 
-	require.Equal(t, wantObj, gotObj, "output did not match golden file %s", goldenPath)
+func hasJSONOverrides(value any) bool {
+	switch typedValue := value.(type) {
+	case nil:
+		return false
+	case map[string]any:
+		return len(typedValue) > 0
+	case []any:
+		return len(typedValue) > 0
+	default:
+		return true
+	}
 }
 
-func deepMergeMaps(base, override map[string]any) {
+func MergeJSONValues(base, override any) any {
+	baseObj, baseIsObj := base.(map[string]any)
+	overrideObj, overrideIsObj := override.(map[string]any)
+	if baseIsObj && overrideIsObj {
+		return mergeJSONMaps(baseObj, overrideObj)
+	}
+
+	baseArray, baseIsArray := base.([]any)
+	overrideArray, overrideIsArray := override.([]any)
+	if baseIsArray && overrideIsArray {
+		return mergeJSONArrays(baseArray, overrideArray)
+	}
+
+	return override
+}
+
+func mergeJSONMaps(base, override map[string]any) map[string]any {
+	merged := maps.Clone(base)
 	for key, overrideValue := range override {
-		baseValue, ok := base[key]
+		baseValue, ok := merged[key]
 		if !ok {
-			base[key] = overrideValue
+			merged[key] = overrideValue
 			continue
 		}
 
-		baseObj, baseIsObj := baseValue.(map[string]any)
-		overrideObj, overrideIsObj := overrideValue.(map[string]any)
-		if baseIsObj && overrideIsObj {
-			deepMergeMaps(baseObj, overrideObj)
+		merged[key] = MergeJSONValues(baseValue, overrideValue)
+	}
+	return merged
+}
+
+func mergeJSONArrays(base, override []any) []any {
+	merged := slices.Clone(base)
+	for index, overrideValue := range override {
+		if index >= len(merged) {
+			merged = append(merged, overrideValue)
 			continue
 		}
 
-		base[key] = overrideValue
+		merged[index] = MergeJSONValues(merged[index], overrideValue)
 	}
+	return merged
 }

internal/testutil/testutil_test.go

@@ -0,0 +1,91 @@
+package testutil_test
+
+import (
+	"testing"
+
+	"github.com/arm/topo/internal/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMergeJSONValues(t *testing.T) {
+	tests := []struct {
+		name     string
+		base     any
+		override any
+		want     any
+	}{
+		{
+			name: "merges nested maps",
+			base: map[string]any{
+				"name": "service",
+				"metadata": map[string]any{
+					"version": "1.0",
+					"status":  "old",
+				},
+			},
+			override: map[string]any{
+				"metadata": map[string]any{
+					"status": "new",
+				},
+			},
+			want: map[string]any{
+				"name": "service",
+				"metadata": map[string]any{
+					"version": "1.0",
+					"status":  "new",
+				},
+			},
+		},
+		{
+			name: "merges nested arrays by index",
+			base: []any{
+				map[string]any{
+					"name": "first",
+					"checks": []any{
+						map[string]any{"status": "old", "name": "nested"},
+					},
+				},
+				map[string]any{"name": "second"},
+			},
+			override: []any{
+				map[string]any{
+					"checks": []any{
+						map[string]any{"status": "new"},
+					},
+				},
+			},
+			want: []any{
+				map[string]any{
+					"name": "first",
+					"checks": []any{
+						map[string]any{"status": "new", "name": "nested"},
+					},
+				},
+				map[string]any{"name": "second"},
+			},
+		},
+		{
+			name: "appends extra array overrides",
+			base: []any{"first"},
+			override: []any{
+				nil,
+				"second",
+			},
+			want: []any{nil, "second"},
+		},
+		{
+			name:     "replaces mismatched values",
+			base:     map[string]any{"name": "old"},
+			override: "new",
+			want:     "new",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := testutil.MergeJSONValues(tt.base, tt.override)
+
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}