Centralize trusted JSON value cloning

internal/jsonvalue/trusted_test.go

@@ -0,0 +1,27 @@
+package jsonvalue
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+type trustedNamed string
+
+func TestCloneTrustedPreservesTypesAndDetaches(t *testing.T) {
+	named := trustedNamed("value")
+	original := map[string]any{"": map[string]any{"number": json.Number("9007199254740993")}, "typed": []string{"original"}, "pointer": &named, "nilmap": map[string]any(nil), "nilslice": []string(nil), "empty": []any{}}
+	copy := CloneTrusted(original).(map[string]any)
+	if !reflect.DeepEqual(copy, original) {
+		t.Fatalf("clone = %#v", copy)
+	}
+	copy[""].(map[string]any)["number"] = json.Number("1")
+	copy["typed"].([]string)[0] = "changed"
+	*copy["pointer"].(*trustedNamed) = "changed"
+	if original[""].(map[string]any)["number"] != json.Number("9007199254740993") || original["typed"].([]string)[0] != "original" || named != "value" {
+		t.Fatal("clone shares mutable storage")
+	}
+	if copy["nilmap"].(map[string]any) != nil || copy["nilslice"].([]string) != nil || copy["empty"].([]any) == nil {
+		t.Fatal("nil/empty shape changed")
+	}
+}