From 83c2da58f9fa088f9f44eca4a424bfe16120b72a Mon Sep 17 00:00:00 2001
From: Arda TANRIKULU <20847995+ardatan@users.noreply.github.com>
Date: Thu, 15 Aug 2019 09:57:29 -0400
Subject: [PATCH] Able to provide custom fetch implementation (#2369)

* Able to provide custom fetch implementation

* Fix tests
---
 packages/graphql-codegen-cli/src/load.ts        |  6 ++++++
 .../tests/__mocks__/some-fetch.js               | 14 ++++++++++++++
 .../graphql-codegen-cli/tests/codegen.spec.ts   | 17 ++++++++++++++++-
 packages/utils/plugins-helpers/src/types.ts     |  1 +
 4 files changed, 37 insertions(+), 1 deletion(-)
 create mode 100644 packages/graphql-codegen-cli/tests/__mocks__/some-fetch.js

diff --git a/packages/graphql-codegen-cli/src/load.ts b/packages/graphql-codegen-cli/src/load.ts
index 1cec28be782..4951fe84fba 100644
--- a/packages/graphql-codegen-cli/src/load.ts
+++ b/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);
diff --git a/packages/graphql-codegen-cli/tests/__mocks__/some-fetch.js b/packages/graphql-codegen-cli/tests/__mocks__/some-fetch.js
new file mode 100644
index 00000000000..5c70acef525
--- /dev/null
+++ b/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);
+      },
+    };
+  },
+};
diff --git a/packages/graphql-codegen-cli/tests/codegen.spec.ts b/packages/graphql-codegen-cli/tests/codegen.spec.ts
index 8f6e525b51a..b0c54134ca5 100644
--- a/packages/graphql-codegen-cli/tests/codegen.spec.ts
+++ b/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();
+  });
 });
diff --git a/packages/utils/plugins-helpers/src/types.ts b/packages/utils/plugins-helpers/src/types.ts
index 79f010390b0..b73f370388d 100644
--- a/packages/utils/plugins-helpers/src/types.ts
+++ b/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 };