Able to provide custom fetch implementation (#2369)

* Able to provide custom fetch implementation

* Fix tests

packages/graphql-codegen-cli/src/load.ts

@@ -67,6 +67,12 @@ export const loadSchema = async (schemaDef: Types.Schema, config: Types.Config):
       options.tagPluck = config.pluckConfig;
     }
 
+    if (config.customFetch) {
+      const customFetchStr = config.customFetch;
+      const [moduleName, fetchFnName] = customFetchStr.split('#');
+      options.fetch = await import(moduleName).then(module => (fetchFnName ? module[fetchFnName] : module));
+    }
+
     const docs = (await loadTypedefs(pointToSchema, options)).map(({ content }) => content);
 
     return mergeTypeDefs(docs);

packages/graphql-codegen-cli/tests/__mocks__/some-fetch.js

@@ -0,0 +1,14 @@
+const { readFileSync } = require('fs');
+const { buildSchema, graphql, introspectionQuery } = require('graphql');
+module.exports = {
+  someFetchFn: async (url, options) => {
+    const schemaFile = readFileSync(__dirname + '/../test-documents/schema.graphql', 'utf8');
+    const schema = buildSchema(schemaFile);
+    return {
+      json() {
+        global.CUSTOM_FETCH_FN_CALLED = true;
+        return graphql(schema, introspectionQuery);
+      },
+    };
+  },
+};

packages/graphql-codegen-cli/tests/codegen.spec.ts

@@ -1,12 +1,15 @@
 import { Types } from '@graphql-codegen/plugin-helpers';
 import '@graphql-codegen/testing';
-import { GraphQLObjectType, buildSchema, buildASTSchema, parse, print } from 'graphql';
+import { GraphQLObjectType, buildSchema, buildASTSchema, parse, print, buildClientSchema, graphql, getIntrospectionQuery } from 'graphql';
 import { mergeSchemas } from '@graphql-codegen/core';
 import { executeCodegen } from '../src';
+import { readFileSync } from 'fs';
 
 const SHOULD_NOT_THROW_STRING = 'SHOULD_NOT_THROW';
 const SIMPLE_TEST_SCHEMA = `type MyType { f: String } type Query { f: String }`;
 
+jest.mock('some-fetch');
+
 describe('Codegen Executor', () => {
   describe('Generator General Options', () => {
     it('Should output the correct filenames', async () => {
@@ -870,4 +873,16 @@ describe('Codegen Executor', () => {
       }
     });
   });
+
+  it('should load schema with custom fetch', async () => {
+    await executeCodegen({
+      schema: ['http://www.dummyschema.com/graphql'],
+      customFetch: 'some-fetch#someFetchFn',
+      documents: ['./tests/test-documents/valid.graphql'],
+      generates: {
+        'out1.ts': ['typescript'],
+      },
+    });
+    expect(global['CUSTOM_FETCH_FN_CALLED']).toBeTruthy();
+  });
 });

packages/utils/plugins-helpers/src/types.ts

@@ -92,6 +92,7 @@ export namespace Types {
   export interface Config {
     schema?: InstanceOrArray<Schema>;
     require?: RequireExtension;
+    customFetch?: string;
     documents?: InstanceOrArray<OperationDocument>;
     config?: { [key: string]: any };
     generates: { [output: string]: OutputConfig | ConfiguredOutput };