fix #100: only look for "unknown keyword" if the uri contains a pointer.

src/json-validator.cpp

@@ -177,6 +177,10 @@ public:
 			return schema->second;
 
 		// referencing an unknown keyword, turn it into schema
+		//
+		// an unknown keyword can only be referenced by a json-pointer,
+		// not by a plain name fragment
+		if (uri.pointer() != "") {
 			try {
 				auto &subschema = file.unknown_keywords.at(uri.pointer()); // null is returned if not existing
 				auto s = schema::make(subschema, this, {}, {{uri}});       //  A JSON Schema MUST be an object or a boolean.
@@ -186,6 +190,7 @@ public:
 				}
 			} catch (nlohmann::detail::out_of_range &) { // at() did not find it
 			}
+		}
 
 		// get or create a schema_ref
 		auto r = file.unresolved.lower_bound(uri.fragment());

test/issue-100/CMakeLists.txt

@@ -0,0 +1,6 @@
+add_test_simple_schema(Issue::100
+                       ${CMAKE_CURRENT_SOURCE_DIR}/schema.json
+                       ${CMAKE_CURRENT_SOURCE_DIR}/instance.json)
+set_tests_properties(Issue::100
+                     PROPERTIES
+                         WILL_FAIL 1)

test/issue-100/instance.json

@@ -0,0 +1,4 @@
+{
+    "Prop1": 1,
+    "Prop2": []
+}

test/issue-100/schema.json

@@ -0,0 +1,15 @@
+{
+    "$id": "http://xxx.local/schemas/mySchema.json",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+
+    "type": "object",
+    "properties": {
+        "Prop1": {
+            "type": "integer",
+            "$comment": "Just a comment"
+        },
+        "Prop2": {
+            "$ref": "#random_ref"
+        }
+    }
+}