refactor: add separate Ajv schema existence check

Author: ivan-tymoshenko

index.js

@@ -111,9 +111,15 @@ function build (schema, options) {
       }
 
       if (refResolver.getSchema(schemaKey) === undefined) {
-        ajvInstance.addSchema(externalSchema, schemaKey)
         refResolver.addSchema(externalSchema, key)
       }
+
+      if (
+        ajvInstance.refs[schemaKey] === undefined &&
+        ajvInstance.schemas[schemaKey] === undefined
+      ) {
+        ajvInstance.addSchema(externalSchema, schemaKey)
+      }
     }
   }