fix(repository-json-schema): resolve the circular reference

Author: jannyHou

packages/repository-json-schema/src/__tests__/integration/build-schema.integration.ts

@@ -591,6 +591,45 @@ describe('build-schema', () => {
       });
     });
 
+    context('model conversion', () => {
+      @model()
+      class Category {
+        @property.array(() => Product)
+        products?: Product[];
+      }
+
+      @model()
+      class Product {
+        @property(() => Category)
+        category?: Category;
+      }
+
+      const expectedSchema = {
+        title: 'Category',
+        properties: {
+          products: {
+            type: 'array',
+            items: {$ref: '#/definitions/Product'},
+          },
+        },
+        definitions: {
+          Product: {
+            title: 'Product',
+            properties: {
+              category: {
+                $ref: '#/definitions/Category',
+              },
+            },
+          },
+        },
+      };
+
+      it('handles circular references', () => {
+        const schema = modelToJsonSchema(Category);
+        expect(schema).to.deepEqual(expectedSchema);
+      });
+    });
+
     function expectValidJsonSchema(schema: JsonSchema) {
       const ajv = new Ajv();
       const validate = ajv.compile(
@@ -641,5 +680,54 @@ describe('build-schema', () => {
         },
       });
     });
+    it('does not pollute the JSON schema options', () => {
+      @model()
+      class Category {
+        @property()
+        name: string;
+      }
+
+      const JSON_SCHEMA_OPTIONS = {};
+      getJsonSchema(Category, JSON_SCHEMA_OPTIONS);
+      expect(JSON_SCHEMA_OPTIONS).to.be.empty();
+    });
+    context('circular reference', () => {
+      @model()
+      class Category {
+        @property.array(() => Product)
+        products?: Product[];
+      }
+
+      @model()
+      class Product {
+        @property(() => Category)
+        category?: Category;
+      }
+
+      const expectedSchemaForCategory = {
+        title: 'Category',
+        properties: {
+          products: {
+            type: 'array',
+            items: {$ref: '#/definitions/Product'},
+          },
+        },
+        definitions: {
+          Product: {
+            title: 'Product',
+            properties: {
+              category: {
+                $ref: '#/definitions/Category',
+              },
+            },
+          },
+        },
+      };
+
+      it('generates the schema without running into infinite loop', () => {
+        const schema = getJsonSchema(Category);
+        expect(schema).to.deepEqual(expectedSchemaForCategory);
+      });
+    });
   });
 });

packages/repository-json-schema/src/build-schema.ts

@@ -14,18 +14,27 @@ import {
 import {JSONSchema6 as JSONSchema} from 'json-schema';
 import {JSON_SCHEMA_KEY} from './keys';
 
+export interface JsonSchemaOptions {
+  visited?: {[key: string]: JSONSchema};
+}
+
 /**
  * Gets the JSON Schema of a TypeScript model/class by seeing if one exists
  * in a cache. If not, one is generated and then cached.
  * @param ctor Contructor of class to get JSON Schema from
  */
-export function getJsonSchema(ctor: Function): JSONSchema {
-  // NOTE(shimks) currently impossible to dynamically update
-  const jsonSchema = MetadataInspector.getClassMetadata(JSON_SCHEMA_KEY, ctor);
-  if (jsonSchema) {
-    return jsonSchema;
+export function getJsonSchema(
+  ctor: Function,
+  options?: JsonSchemaOptions,
+): JSONSchema {
+  // In the near future the metadata will be an object with
+  // different titles as keys
+  const cached = MetadataInspector.getClassMetadata(JSON_SCHEMA_KEY, ctor);
+
+  if (cached) {
+    return cached;
   } else {
-    const newSchema = modelToJsonSchema(ctor);
+    const newSchema = modelToJsonSchema(ctor, options);
     MetadataInspector.defineMetadata(JSON_SCHEMA_KEY.key, newSchema, ctor);
     return newSchema;
   }
@@ -142,16 +151,26 @@ export function metaToJsonProperty(meta: PropertyDefinition): JSONSchema {
  * reflection API
  * @param ctor Constructor of class to convert from
  */
-export function modelToJsonSchema(ctor: Function): JSONSchema {
+export function modelToJsonSchema(
+  ctor: Function,
+  jsonSchemaOptions: JsonSchemaOptions = {},
+): JSONSchema {
+  const options = {...jsonSchemaOptions};
+  options.visited = options.visited || {};
+
   const meta: ModelDefinition | {} = ModelMetadataHelper.getModelMetadata(ctor);
-  const result: JSONSchema = {};
 
   // returns an empty object if metadata is an empty object
   if (!(meta instanceof ModelDefinition)) {
     return {};
   }
 
-  result.title = meta.title || ctor.name;
+  const title = meta.title || ctor.name;
+
+  if (options.visited[title]) return options.visited[title];
+
+  const result: JSONSchema = {title};
+  options.visited[title] = result;
 
   if (meta.description) {
     result.description = meta.description;
@@ -190,20 +209,24 @@ export function modelToJsonSchema(ctor: Function): JSONSchema {
       continue;
     }
 
-    const propSchema = getJsonSchema(referenceType);
+    const propSchema = getJsonSchema(referenceType, options);
+
+    includeReferencedSchema(referenceType.name, propSchema);
 
-    if (propSchema && Object.keys(propSchema).length > 0) {
+    function includeReferencedSchema(name: string, schema: JSONSchema) {
+      if (!schema || !Object.keys(schema).length) return;
       result.definitions = result.definitions || {};
 
-      // delete nested definition
-      if (propSchema.definitions) {
-        for (const key in propSchema.definitions) {
-          result.definitions[key] = propSchema.definitions[key];
+      // promote nested definition to the top level
+      if (schema.definitions) {
+        for (const key in schema.definitions) {
+          if (key === title) continue;
+          result.definitions[key] = schema.definitions[key];
         }
-        delete propSchema.definitions;
+        delete schema.definitions;
       }
 
-      result.definitions[referenceType.name] = propSchema;
+      result.definitions[name] = schema;
     }
   }
   return result;