Wrap schemas using a relative default URI identifier (#1701)

Fixes: #1700
See: sourcemeta/jsonschema#338
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/core/jsonschema/jsonschema.cc

@@ -731,7 +731,10 @@ auto sourcemeta::core::wrap(const sourcemeta::core::JSON &schema,
   // at least an artificial one, otherwise a standalone instance of `$schema`
   // outside of the root of a schema resource is not valid according to
   // JSON Schema
-  constexpr auto WRAPPER_IDENTIFIER{"tag:core.sourcemeta.com,2025:wrap"};
+  // However, note that we use a relative URI so that references to
+  // other schemas whose top-level identifiers are relative URIs don't
+  // get affected. Otherwise, we would cause unintended base resolution.
+  constexpr auto WRAPPER_IDENTIFIER{"__sourcemeta-core-wrap__"};
   const auto id{identify(copy, resolver, SchemaIdentificationStrategy::Strict,
                          default_dialect)
                     .value_or(WRAPPER_IDENTIFIER)};

test/jsonschema/jsonschema_wrap_test.cc

@@ -54,11 +54,11 @@ TEST(JSONSchema_wrap, schema_without_identifier) {
 
   const auto expected{sourcemeta::core::parse_json(R"JSON({
     "$schema": "https://json-schema.org/draft/2020-12/schema",
-    "$ref": "tag:core.sourcemeta.com,2025:wrap#/items",
+    "$ref": "__sourcemeta-core-wrap__#/items",
     "$defs": {
       "schema": {
         "$schema": "https://json-schema.org/draft/2020-12/schema",
-        "$id": "tag:core.sourcemeta.com,2025:wrap",
+        "$id": "__sourcemeta-core-wrap__",
         "items": {
           "type": "string"
         }
@@ -69,6 +69,36 @@ TEST(JSONSchema_wrap, schema_without_identifier) {
   EXPECT_EQ(result, expected);
 }
 
+TEST(JSONSchema_wrap, schema_without_identifier_and_relative_uri) {
+  const auto schema{sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "items": {
+      "$ref": "relative"
+    }
+  })JSON")};
+
+  const auto result{sourcemeta::core::wrap(
+      schema, {"items"}, sourcemeta::core::schema_official_resolver)};
+
+  // We don't want the relative reference to be resolved against
+  // an absolute base
+  const auto expected{sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$ref": "__sourcemeta-core-wrap__#/items",
+    "$defs": {
+      "schema": {
+        "$schema": "https://json-schema.org/draft/2020-12/schema",
+        "$id": "__sourcemeta-core-wrap__",
+        "items": {
+          "$ref": "relative"
+        }
+      }
+    }
+  })JSON")};
+
+  EXPECT_EQ(result, expected);
+}
+
 TEST(JSONSchema_wrap, schema_without_identifier_with_default_dialect) {
   const auto schema{sourcemeta::core::parse_json(R"JSON({
     "items": {
@@ -82,11 +112,11 @@ TEST(JSONSchema_wrap, schema_without_identifier_with_default_dialect) {
 
   const auto expected{sourcemeta::core::parse_json(R"JSON({
     "$schema": "https://json-schema.org/draft/2020-12/schema",
-    "$ref": "tag:core.sourcemeta.com,2025:wrap#/items",
+    "$ref": "__sourcemeta-core-wrap__#/items",
     "$defs": {
       "schema": {
         "$schema": "https://json-schema.org/draft/2020-12/schema",
-        "$id": "tag:core.sourcemeta.com,2025:wrap",
+        "$id": "__sourcemeta-core-wrap__",
         "items": {
           "type": "string"
         }
@@ -112,11 +142,11 @@ TEST(JSONSchema_wrap,
 
   const auto expected{sourcemeta::core::parse_json(R"JSON({
     "$schema": "https://json-schema.org/draft/2020-12/schema",
-    "$ref": "tag:core.sourcemeta.com,2025:wrap#/items",
+    "$ref": "__sourcemeta-core-wrap__#/items",
     "$defs": {
       "schema": {
         "$schema": "https://json-schema.org/draft/2020-12/schema",
-        "$id": "tag:core.sourcemeta.com,2025:wrap",
+        "$id": "__sourcemeta-core-wrap__",
         "items": {
           "type": "string"
         }