Allow 'headers' resolver option to be a function

Signed-off-by: Yoon Lee <himynameisyoon@gmail.com>

Author: Yoon Lee

packages/openapi-to-graphql/README.md

@@ -170,7 +170,7 @@ Schema options:
 
 Resolver options:
 
-- `headers` (type: `object`, default: `{}`): OpenAPI-to-GraphQL, by default, will create arguments for header parameters. This option allows users to stop this behavior and manually inject headers into resolver calls. 
+- `headers` (type: `object` | `function`, default: `{}`): Headers to be sent in every request to the API described by the given OAS. Parameters defined in the OpenAPI Specification to set these headers will be ignored by OpenAPI-to-GraphQL. If used as a function, the following parameters will be exposed per-request: `req` (the GraphQL resolver's context.request object), `method`, `path`, and `title`.
 
 - `qs` (type: `object`, default: `{}`): Query parameters to be sent in every request to the API described by the given OAS. Parameters defined in the OpenAPI Specification to set these query parameters will be ignored by OpenAPI-to-GraphQL.
 

packages/openapi-to-graphql/lib/resolver_builder.d.ts

@@ -3,6 +3,12 @@ import { Operation } from './types/operation';
 import { ResolveFunction, SubscriptionIterator } from './types/graphql';
 import { PreprocessingData } from './types/preprocessing_data';
 import * as NodeRequest from 'request';
+import { RequestHeadersFunction } from './types/options';
+declare type RequestOptions = Omit<NodeRequest.OptionsWithUrl, 'headers'> & {
+    headers: {
+        [key: string]: string;
+    } | RequestHeadersFunction;
+};
 declare type GetResolverParams = {
     operation: Operation;
     argsFromLink?: {
@@ -12,7 +18,7 @@ declare type GetResolverParams = {
     responseName?: string;
     data: PreprocessingData;
     baseUrl?: string;
-    requestOptions?: NodeRequest.OptionsWithUrl;
+    requestOptions?: RequestOptions;
 };
 declare type GetSubscribeParams = {
     operation: Operation;

packages/openapi-to-graphql/lib/resolver_builder.js

@@ -18,6 +18,7 @@ import {
 } from './types/graphql'
 import { PreprocessingData } from './types/preprocessing_data'
 import * as NodeRequest from 'request'
+import { RequestHeadersFunction } from './types/options'
 
 // Imports:
 import * as Oas3Tools from './oas_3_tools'
@@ -46,14 +47,18 @@ type AuthOptions = {
   authCookie: NodeRequest.Cookie
 }
 
+type RequestOptions = Omit<NodeRequest.OptionsWithUrl, 'headers'> & {
+  headers: { [key: string]: string } | RequestHeadersFunction
+}
+
 type GetResolverParams = {
   operation: Operation
   argsFromLink?: { [key: string]: string }
   payloadName?: string
   responseName?: string
   data: PreprocessingData
   baseUrl?: string
-  requestOptions?: NodeRequest.OptionsWithUrl
+  requestOptions?: RequestOptions
 }
 
 type GetSubscribeParams = {
@@ -458,8 +463,18 @@ export function getResolver({
       options = { ...requestOptions }
       options['method'] = operation.method
       options['url'] = url
-      if (options.headers) {
-        Object.assign(options.headers, headers)
+      if (requestOptions.headers) {
+        if (typeof requestOptions.headers === 'object') {
+          Object.assign(requestOptions.headers, headers)
+        } else if (typeof requestOptions.headers === 'function') {
+          const val = requestOptions.headers({
+            req: (ctx as any).request,
+            method,
+            path,
+            title
+          })
+          Object.assign(options.headers, val)
+        }
       } else {
         options['headers'] = headers
       }

packages/openapi-to-graphql/lib/resolver_builder.js.map

@@ -5,7 +5,7 @@
 
 // Type imports:
 import * as NodeRequest from 'request'
-import { ResolveFunction, ResolveObject, GraphQLOperationType } from './graphql'
+import { GraphQLOperationType } from './graphql'
 
 /**
  * Type definition of the options that users can pass to OpenAPI-to-GraphQL.
@@ -43,6 +43,13 @@ export type OasTitlePathMethodObject<T> = {
 
 export type Options = Partial<InternalOptions>
 
+export type RequestHeadersFunction = (params: {
+  req: any
+  method: string
+  path: string
+  title: string
+}) => object
+
 export type InternalOptions = {
   /**
    * Adhere to the OAS as closely as possible. If set to true, any deviation
@@ -152,7 +159,7 @@ export type InternalOptions = {
   /**
    * Custom headers to send with every request made by a resolve function.
    */
-  headers?: { [key: string]: string }
+  headers?: { [key: string]: string } | RequestHeadersFunction
 
   /**
    * Custom query parameters to send with every reqeust by a resolve function.