Ensure that arrays are properly supported

src/RewriteHandler.ts

@@ -72,8 +72,10 @@ export default class RewriteHandler {
     let rewrittenResponse = response;
     this.matches.reverse().forEach(({ rewriter, paths }) => {
       paths.forEach(path => {
-        rewrittenResponse = rewriteResultsAtPath(rewrittenResponse, path, (parentResponse, key) =>
-          rewriter.rewriteResponse(parentResponse, key)
+        rewrittenResponse = rewriteResultsAtPath(
+          rewrittenResponse,
+          path,
+          (parentResponse, key, index) => rewriter.rewriteResponse(parentResponse, key, index)
         );
       });
     });

src/ast.ts

@@ -261,7 +261,7 @@ interface ResultObj {
 export const rewriteResultsAtPath = (
   results: ResultObj,
   path: ReadonlyArray<string>,
-  callback: (parentResult: any, key: string | number) => any
+  callback: (parentResult: any, key: string, position?: number) => any
 ): ResultObj => {
   if (path.length === 0) return results;
 
@@ -271,12 +271,10 @@ export const rewriteResultsAtPath = (
 
   if (path.length === 1) {
     if (Array.isArray(curResults)) {
-      newResults[curPathElm] = curResults.map((_, index) => {
-        const newValue = callback(curResults, index);
-        return newValue;
-      });
-
-      return newResults;
+      return curResults.reduce(
+        (reducedResults, _, index) => callback(reducedResults, curPathElm, index),
+        results
+      );
     }
 
     return callback(results, curPathElm);

src/rewriters/NestFieldOutputsRewriter.ts

@@ -65,23 +65,17 @@ class NestFieldOutputsRewriter extends Rewriter {
     } as NodeAndVarDefs;
   }
 
-  public rewriteResponse(response: any, key: string | number) {
-    const pathResponse = response[key];
+  public rewriteResponse(response: any, key: string, index?: number) {
+    // Extract the element we are working on
+    const element = super.extractReponseElement(response, key, index);
+    if (element === null || typeof element !== 'object') return response;
 
-    if (typeof pathResponse === 'object') {
-      // undo the nesting in the response so it matches the original query
-      if (
-        pathResponse[this.newOutputName] &&
-        typeof pathResponse[this.newOutputName] === 'object'
-      ) {
-        const rewrittenResponse = { ...pathResponse, ...pathResponse[this.newOutputName] };
-        delete rewrittenResponse[this.newOutputName];
+    // Undo the nesting in the response so it matches the original query
+    if (element[this.newOutputName] && typeof element[this.newOutputName] === 'object') {
+      const newElement = { ...element, ...element[this.newOutputName] };
+      delete newElement[this.newOutputName];
 
-        return {
-          ...response,
-          [key]: rewrittenResponse
-        };
-      }
+      return super.rewriteResponseElement(response, newElement, key, index);
     }
 
     return response;

src/rewriters/Rewriter.ts

@@ -56,7 +56,57 @@ abstract class Rewriter {
     return variables;
   }
 
-  public rewriteResponse(response: any, key: string | number): any {
+  /*
+   * Receives the parent object of the matched field with the key of the matched field.
+   * For arrays, the index of the element is also present.
+   */
+  public rewriteResponse(response: any, key: string, index?: number): any {
+    return response;
+  }
+
+  /*
+   * Helper that extracts the element from the response if possible otherwise returns null.
+   */
+  protected extractReponseElement(response: any, key: string, index?: number): any {
+    // Verify the response format
+    let element = null;
+    if (response === null || typeof response !== 'object') return element;
+
+    // Extract the key
+    element = response[key] || null;
+
+    // Extract the position
+    if (Array.isArray(element)) {
+      element = element[index!] || null;
+    }
+
+    return element;
+  }
+
+  /*
+   * Helper that rewrite the element from the response if possible and returns the response.
+   */
+  protected rewriteResponseElement(
+    response: any,
+    newElement: any,
+    key: string,
+    index?: number
+  ): any {
+    // Verify the response format
+    if (response === null || typeof response !== 'object') return response;
+
+    // Extract the key
+    let element = response[key];
+
+    // Extract the position
+    // NOTE: We might eventually want to create an array if one is not present at the key
+    // and we receive an index in input
+    if (Array.isArray(element)) {
+      element[index!] = newElement;
+    } else {
+      response[key] = newElement;
+    }
+
     return response;
   }
 }

src/rewriters/ScalarFieldToObjectFieldRewriter.ts

@@ -7,7 +7,7 @@ interface ScalarFieldToObjectFieldRewriterOpts extends RewriterOpts {
 }
 
 /**
- * Rewriter which nests output fields inside of a new output object
+ * Rewriter which nests a scalar field inside of a new output object
  * ex: change from `field { subField }` to `field { subField { objectfield } }`
  */
 class ScalarFieldToObjectFieldRewriter extends Rewriter {
@@ -48,18 +48,14 @@ class ScalarFieldToObjectFieldRewriter extends Rewriter {
     } as NodeAndVarDefs;
   }
 
-  public rewriteResponse(response: any, key: string | number) {
-    if (typeof response === 'object') {
-      const pathResponse = response[key];
+  public rewriteResponse(response: any, key: string, index?: number) {
+    // Extract the element we are working on
+    const element = super.extractReponseElement(response, key, index);
+    if (element === null) return response;
 
-      // undo the nesting in the response so it matches the original query
-      return {
-        ...response,
-        [key]: pathResponse[this.objectFieldName]
-      };
-    }
-
-    return response;
+    // Undo the nesting in the response so it matches the original query
+    const newElement = element[this.objectFieldName];
+    return super.rewriteResponseElement(response, newElement, key, index);
   }
 }
 

src/rewriters/index.ts

@@ -1,4 +1,4 @@
-export { default as Rewriter } from './Rewriter';
+export { default as Rewriter, RewriterOpts } from './Rewriter';
 export { default as FieldArgNameRewriter } from './FieldArgNameRewriter';
 export { default as FieldArgsToInputTypeRewriter } from './FieldArgsToInputTypeRewriter';
 export { default as FieldArgTypeRewriter } from './FieldArgTypeRewriter';

test/ast.test.ts

@@ -68,10 +68,10 @@ describe('ast utils', () => {
         ]
       });
       expect(
-        rewriteResultsAtPath(obj, ['things', 'moreThings'], (elm, path) => ({
-          ...elm[path],
-          meh: '7'
-        }))
+        rewriteResultsAtPath(obj, ['things', 'moreThings'], (elm, path, index) => {
+          elm[path][index!] = { ...elm[path][index!], meh: '7' };
+          return elm;
+        })
       ).toEqual({
         things: [
           {

test/functional/rewriteNestFieldOutputs.test.ts

@@ -2,7 +2,7 @@ import RewriteHandler from '../../src/RewriteHandler';
 import NestFieldOutputsRewriter from '../../src/rewriters/NestFieldOutputsRewriter';
 import { gqlFmt } from '../testUtils';
 
-describe('Rewrite field args to input type', () => {
+describe('Rewrite output fields inside of a new output object', () => {
   it('allows nesting the args provided into an input type', () => {
     const handler = new RewriteHandler([
       new NestFieldOutputsRewriter({
@@ -102,4 +102,58 @@ describe('Rewrite field args to input type', () => {
       }
     });
   });
+
+  it('allows nesting the args provided in an array', () => {
+    const handler = new RewriteHandler([
+      new NestFieldOutputsRewriter({
+        fieldName: 'createCats',
+        newOutputName: 'cat',
+        outputsToNest: ['name', 'color', 'id']
+      })
+    ]);
+    const query = gqlFmt`
+      mutation createManyCats {
+        createCats {
+          id
+          name
+          color
+        }
+      }
+    `;
+    const expectedRewritenQuery = gqlFmt`
+      mutation createManyCats {
+        createCats {
+          cat {
+            id
+            name
+            color
+          }
+        }
+      }
+    `;
+    expect(handler.rewriteRequest(query)).toEqual({
+      query: expectedRewritenQuery
+    });
+    expect(
+      handler.rewriteResponse({
+        createCats: [
+          {
+            cat: {
+              id: 1,
+              name: 'jack',
+              color: 'blue'
+            }
+          }
+        ]
+      })
+    ).toEqual({
+      createCats: [
+        {
+          id: 1,
+          name: 'jack',
+          color: 'blue'
+        }
+      ]
+    });
+  });
 });

test/functional/rewriteScalarFieldToObjectField.test.ts

@@ -3,7 +3,7 @@ import ScalarFieldToObjectFieldRewriter from '../../src/rewriters/ScalarFieldToO
 import { gqlFmt } from '../testUtils';
 
 describe('Rewrite scalar field to be a nested object with a single scalar field', () => {
-  it('rewrites a scalar field to be an objet field with 1 scalar subfield', () => {
+  it('rewrites a scalar field to be an object field with 1 scalar subfield', () => {
     const handler = new RewriteHandler([
       new ScalarFieldToObjectFieldRewriter({
         fieldName: 'title',
@@ -226,4 +226,48 @@ describe('Rewrite scalar field to be a nested object with a single scalar field'
       }
     });
   });
+
+  it('rewrites a scalar field array to be an array of object fields with 1 scalar subfield', () => {
+    const handler = new RewriteHandler([
+      new ScalarFieldToObjectFieldRewriter({
+        fieldName: 'titles',
+        objectFieldName: 'text'
+      })
+    ]);
+
+    const query = gqlFmt`
+      query getThing {
+        thing {
+          titles
+        }
+      }
+    `;
+    const expectedRewritenQuery = gqlFmt`
+      query getThing {
+        thing {
+          titles {
+            text
+          }
+        }
+      }
+    `;
+    expect(handler.rewriteRequest(query)).toEqual({
+      query: expectedRewritenQuery
+    });
+    expect(
+      handler.rewriteResponse({
+        thing: {
+          titles: [
+            {
+              text: 'THING'
+            }
+          ]
+        }
+      })
+    ).toEqual({
+      thing: {
+        titles: ['THING']
+      }
+    });
+  });
 });

test/functional/rewriter.test.ts

@@ -0,0 +1,86 @@
+import Rewriter, { RewriterOpts } from '../../src/rewriters/Rewriter';
+
+describe('rewriter', () => {
+  class TestRewriter extends Rewriter {
+    constructor(options: RewriterOpts) {
+      super(options);
+    }
+
+    public extractReponseElement(response: any, key: string, index?: number): any {
+      return super.extractReponseElement(response, key, index);
+    }
+
+    public rewriteResponseElement(
+      response: any,
+      newElement: any,
+      key: string,
+      index?: number
+    ): any {
+      return super.rewriteResponseElement(response, newElement, key, index);
+    }
+  }
+
+  describe('extractResponseElement', () => {
+    const rewriter = new TestRewriter({ fieldName: 'test' });
+
+    it('can extract element in object', () => {
+      const key = 'key';
+      const element = { a: 1 };
+      const response = { [key]: element };
+
+      expect(rewriter.extractReponseElement(response, key)).toEqual(element);
+    });
+
+    it('can extract element in array', () => {
+      const key = 'key';
+      const element = { a: 1 };
+      const response = { [key]: [element] };
+
+      expect(rewriter.extractReponseElement(response, key, 0)).toEqual(element);
+    });
+
+    it('does not fail on null, empty or malformed response', () => {
+      const key = 'key';
+
+      expect(rewriter.extractReponseElement(null, key)).toEqual(null);
+      expect(rewriter.extractReponseElement('string', key)).toEqual(null);
+      expect(rewriter.extractReponseElement({ a: 1 }, key)).toEqual(null);
+    });
+  });
+
+  describe('rewriteResponseElement', () => {
+    const rewriter = new TestRewriter({ fieldName: 'test' });
+
+    it('can replace element in object', () => {
+      const key = 'key';
+      const newElement = { a: 1 };
+      const response = { [key]: 1 };
+
+      expect(rewriter.rewriteResponseElement(response, newElement, key)).toEqual({
+        [key]: newElement
+      });
+    });
+
+    it('can replace element in array', () => {
+      const key = 'key';
+      const newElement = { a: 1 };
+      const response = { [key]: [1] };
+
+      expect(rewriter.rewriteResponseElement(response, newElement, key, 0)).toEqual({
+        [key]: [newElement]
+      });
+    });
+
+    it('does not fail on null, empty or malformed response', () => {
+      const key = 'key';
+      const newElement = { a: 1 };
+
+      expect(rewriter.rewriteResponseElement(null, newElement, key)).toEqual(null);
+      expect(rewriter.rewriteResponseElement('string', newElement, key)).toEqual('string');
+      expect(rewriter.rewriteResponseElement({ a: 1 }, newElement, key)).toEqual({
+        a: 1,
+        [key]: newElement
+      });
+    });
+  });
+});