feat: Add transform dereference result hook

src/__tests__/resolver.spec.ts

@@ -1670,6 +1670,183 @@ describe('resolver', () => {
       expect(result.errors[0].uri.toString()).toEqual(new URI('http://foo').toString());
     });
 
+    /**
+     * Allows the consumer to provide a custom ref transformer to transform a fully resolved object.
+     *
+     */
+    test('should support `transformDereferenceResult` hook', async () => {
+      const data = {
+        markdown: '# hello',
+        bar: {
+          hello: `{ "hello": "world" }`,
+        },
+      };
+
+      const source = {
+        definitions: {
+          foo: {
+            $ref: 'http://foo.com/foo.md#/markdown',
+          },
+          bar: {
+            $ref: 'http://foo.com/bar.json#/hello',
+          },
+        },
+      };
+
+      const reader: Types.IResolver = {
+        async resolve(ref: uri.URI): Promise<any> {
+          if (ref.path().split('.')[1] === 'md') {
+            return data;
+          }
+
+          return data.bar;
+        },
+      };
+
+      const resolver = new Resolver({
+        resolvers: {
+          http: reader,
+        },
+        transformDereferenceResult: async opts => {
+          if (opts.parentAuthority.path().split('.')[1] === 'md') {
+            opts.result = {
+              heading1: 'hello',
+            };
+          } else if (opts.parentAuthority.toString() === 'http://foo.com/bar.json' && opts.fragment === '/hello') {
+            // Can transform the result however you want
+            opts.result = {
+              pooh: 'bear',
+            };
+          }
+
+          return opts;
+        },
+      });
+
+      const result = await resolver.resolve(source);
+
+      expect(result.result).toEqual({
+        definitions: {
+          foo: {
+            heading1: 'hello',
+          },
+          bar: {
+            pooh: 'bear',
+          },
+        },
+      });
+    });
+
+    test('should pass `transformDereferenceResult` to child runners', async () => {
+      const data = {
+        foo: {
+          $ref: 'http://foo.com/hi',
+        },
+        hi: {
+          $ref: 'http://foo.com/bye',
+        },
+        bye: {
+          adios: true,
+        },
+        bar: {
+          hello: 'world',
+        },
+      };
+
+      const source = {
+        definitions: {
+          foo: {
+            $ref: 'http://foo.com/foo',
+          },
+          bar: {
+            $ref: 'http://foo.com/bar',
+          },
+        },
+      };
+
+      const reader: Types.IResolver = {
+        async resolve(ref: uri.URI): Promise<any> {
+          return data[ref.path().slice(1)];
+        },
+      };
+
+      let counter = 0;
+      const resolver = new Resolver({
+        resolvers: {
+          http: reader,
+        },
+        transformDereferenceResult: async opts => {
+          counter += 1;
+          return opts;
+        },
+      });
+
+      const result = await resolver.resolve(source);
+
+      expect(result.result).toEqual({
+        definitions: {
+          foo: {
+            adios: true,
+          },
+          bar: {
+            hello: 'world',
+          },
+        },
+      });
+
+      expect(counter).toEqual(5);
+    });
+
+    test('should support catching error in `transformDereferenceResult` hook', async () => {
+      const data = {
+        markdown: '# hello',
+      };
+
+      const source = {
+        definitions: {
+          foo: {
+            $ref: 'http://foo.com#/markdown',
+          },
+        },
+      };
+
+      const reader: Types.IResolver = {
+        async resolve(): Promise<any> {
+          return data;
+        },
+      };
+
+      const resolver = new Resolver({
+        resolvers: {
+          http: reader,
+        },
+        transformDereferenceResult: async opts => {
+          if (opts.parentAuthority.toString() === 'http://foo.com/') throw new Error('some transform error!');
+
+          return opts;
+        },
+      });
+
+      const result = await resolver.resolve(source);
+
+      expect(result.result).toEqual({
+        definitions: {
+          foo: '# hello',
+        },
+      });
+
+      expect({ ...result.errors[0], uri: undefined }).toEqual({
+        code: 'TRANSFORM_DEREFERENCED',
+        message:
+          "Error: Could not transform dereferenced result for 'http://foo.com/#/markdown' - Error: some transform error!",
+        pointerStack: [],
+        uriStack: [],
+        path: ['markdown'],
+        uri: undefined,
+      });
+      expect(result.errors[0].uri.toString()).toEqual(new URI('#/markdown').toString());
+    });
+
     test('should pass context to transformRef and read', async () => {
       let t1;
       let t2;

src/resolver.ts

@@ -20,6 +20,7 @@ export class Resolver {
   protected getRef?: (key: string, val: any) => string | void;
   protected transformRef?: (opts: Types.IRefTransformer, ctx: any) => uri.URI | any;
   protected parseResolveResult?: (opts: Types.IUriParser) => Promise<Types.IUriParserResult>;
+  protected transformDereferenceResult?: (opts: Types.IDereferenceTransformer) => Promise<Types.ITransformerResult>;
 
   constructor(opts: Types.IResolverOpts = {}) {
     this.uriCache = opts.uriCache || new Cache();
@@ -29,6 +30,7 @@ export class Resolver {
     this.dereferenceInline = typeof opts.dereferenceInline !== 'undefined' ? opts.dereferenceInline : true;
     this.dereferenceRemote = typeof opts.dereferenceRemote !== 'undefined' ? opts.dereferenceRemote : true;
     this.parseResolveResult = opts.parseResolveResult;
+    this.transformDereferenceResult = opts.transformDereferenceResult;
     this.ctx = opts.ctx;
   }
 
@@ -41,6 +43,7 @@ export class Resolver {
       dereferenceInline: this.dereferenceInline,
       dereferenceRemote: this.dereferenceRemote,
       parseResolveResult: this.parseResolveResult,
+      transformDereferenceResult: this.transformDereferenceResult,
       ...opts,
       ctx: Object.assign({}, this.ctx || {}, opts.ctx || {}),
     });

src/runner.ts

@@ -38,6 +38,9 @@ export class ResolveRunner implements Types.IResolveRunner {
   public readonly getRef: (key: string, val: any) => string | void;
   public readonly transformRef?: (opts: Types.IRefTransformer, ctx: any) => uri.URI | any;
   public readonly parseResolveResult?: (opts: Types.IUriParser) => Promise<Types.IUriParserResult>;
+  public readonly transformDereferenceResult?: (
+    opts: Types.IDereferenceTransformer,
+  ) => Promise<Types.ITransformerResult>;
 
   private _source: any;
 
@@ -74,6 +77,7 @@ export class ResolveRunner implements Types.IResolveRunner {
 
     this.dereferenceRemote = typeof opts.dereferenceRemote !== 'undefined' ? opts.dereferenceRemote : true;
     this.parseResolveResult = opts.parseResolveResult;
+    this.transformDereferenceResult = opts.transformDereferenceResult;
     this.ctx = opts.ctx;
 
     this.lookupUri = memoize(this.lookupUri, {
@@ -233,6 +237,37 @@ export class ResolveRunner implements Types.IResolveRunner {
       resolved.result = this._source;
     }
 
+    // support custom transformers
+    if (this.transformDereferenceResult) {
+      const ref = new URI(jsonPointer || '');
+      try {
+        const { result, error } = await this.transformDereferenceResult({
+          source: this.source,
+          result: resolved.result,
+          targetAuthority: ref,
+          parentAuthority: this.baseUri,
+          parentPath: targetPath,
+          fragment: ref.fragment(),
+        });
+
+        resolved.result = result;
+        if (error) {
+          throw new Error(`Could not transform dereferenced result for '${ref.toString()}' - ${String(error)}`);
+        }
+      } catch (e) {
+        resolved.errors.push({
+          code: 'TRANSFORM_DEREFERENCED',
+          message: `Error: Could not transform dereferenced result for '${this.baseUri.toString()}${
+            ref.fragment() !== '' ? `#${ref.fragment()}` : ``
+          }' - ${String(e)}`,
+          uri: ref,
+          uriStack: this.uriStack,
+          pointerStack: [],
+          path: targetPath,
+        });
+      }
+    }
+
     return resolved;
   }
 
@@ -340,6 +375,7 @@ export class ResolveRunner implements Types.IResolveRunner {
       resolvers: this.resolvers,
       transformRef: this.transformRef,
       parseResolveResult: this.parseResolveResult,
+      transformDereferenceResult: this.transformDereferenceResult,
       dereferenceRemote: this.dereferenceRemote,
       dereferenceInline: this.dereferenceInline,
       ctx: this.ctx,

src/types.ts

@@ -51,6 +51,13 @@ export interface IResolverOpts {
    */
   parseResolveResult?: (opts: IUriParser) => Promise<IUriParserResult>;
 
+  /**
+   * Hook to transform resolved object.
+   *
+   * For example, transform `OpenAPI` file to a `Hub Page`.
+   */
+  transformDereferenceResult?: (opts: IDereferenceTransformer) => Promise<ITransformerResult>;
+
   /** Should we resolve local pointers? true by default. */
   dereferenceInline?: boolean;
 
@@ -126,6 +133,20 @@ export interface IUriParserResult {
   error?: Error;
 }
 
+export interface IDereferenceTransformer {
+  result: any;
+  source: any;
+  fragment: string;
+  targetAuthority: uri.URI;
+  parentAuthority: uri.URI;
+  parentPath: string[];
+}
+
+export interface ITransformerResult {
+  result?: any;
+  error?: Error;
+}
+
 export interface IUriResult {
   pointerStack: string[];
   targetPath: string[];
@@ -147,7 +168,12 @@ export interface IRefTransformer extends IComputeRefOpts {
   uri: uri.URI;
 }
 
-export type ResolverErrorCode = 'POINTER_MISSING' | 'RESOLVE_URI' | 'PARSE_URI' | 'RESOLVE_POINTER';
+export type ResolverErrorCode =
+  | 'POINTER_MISSING'
+  | 'RESOLVE_URI'
+  | 'PARSE_URI'
+  | 'RESOLVE_POINTER'
+  | 'TRANSFORM_DEREFERENCED';
 export interface IResolveError {
   code: ResolverErrorCode;
   message: string;