Add a 'submitFollow' method to 'Action'

src/action.ts

@@ -2,6 +2,7 @@ import { State } from './state';
 import * as qs from 'querystring';
 import Client from './client';
 import { Field } from './field';
+import Resource from './resource';
 
 export interface ActionInfo {
 
@@ -54,6 +55,17 @@ export interface Action<T extends Record<string, any> = Record<string, any>> ext
    * Return a field by name.
    */
   field(name: string): Field | undefined;
+
+  /**
+   * Execute the action or submit the form, then return the next resource.
+   *
+   * If a server responds with a 201 Status code and a Location header,
+   * it will automatically return the newly created resource.
+   *
+   * If the server responded with a 204 or 205, this function will return
+   * `this`.
+   */
+  submitFollow(formData: T): Promise<Resource>;
 }
 
 export class SimpleAction<TFormData extends Record<string, any>> implements Action {
@@ -113,6 +125,44 @@ export class SimpleAction<TFormData extends Record<string, any>> implements Acti
 
     const uri = new URL(this.uri);
 
+    const newFormData = this.validateForm(formData);
+
+    if (this.method === 'GET') {
+      uri.search = qs.stringify(newFormData);
+      const resource = this.client.go(uri.toString());
+      return resource.get();
+    }
+    const response = await this.fetchOrThrowWithBody(uri, newFormData);
+    const state = this.client.getStateForResponse(uri.toString(), response);
+    return state;
+  }
+
+  async submitFollow(formData: TFormData): Promise<Resource> {
+    const uri = new URL(this.uri);
+
+    const newFormData = this.validateForm(formData);
+
+    if (this.method === 'GET') {
+      uri.search = qs.stringify(newFormData);
+      return this.client.go(uri.toString());
+    }
+
+    const response = await this.fetchOrThrowWithBody(uri, newFormData);
+    switch (response.status) {
+      case 201:
+        if (response.headers.has('location')) {
+          return this.client.go(response.headers.get('location')!);
+        }
+        throw new Error('Could not follow after a 201 request, because the server did not reply with a Location header. If you sent a Location header, check if your service is returning "Access-Control-Expose-Headers: Location".');
+      case 204 :
+      case 205 :
+        return this.client.go(uri.toString());
+      default:
+        throw new Error('Did not receive a 201, 204 or 205 status code so we could not follow to the next resource');
+    }
+  }
+
+  private validateForm(formData: TFormData): TFormData {
     const newFormData: TFormData = {
       ...formData
     };
@@ -132,33 +182,28 @@ export class SimpleAction<TFormData extends Record<string, any>> implements Acti
       }
 
     }
+    return newFormData;
+  }
 
-    if (this.method === 'GET') {
-      uri.search = qs.stringify(newFormData);
-      const resource = this.client.go(uri.toString());
-      return resource.get();
-    }
+  private fetchOrThrowWithBody(uri: URL, formData: TFormData): Promise<Response> {
     let body;
     switch (this.contentType) {
       case 'application/x-www-form-urlencoded' :
-        body = qs.stringify(newFormData);
+        body = qs.stringify(formData);
         break;
       case 'application/json':
-        body = JSON.stringify(newFormData);
+        body = JSON.stringify(formData);
         break;
       default :
         throw new Error(`Serializing mimetype ${this.contentType} is not yet supported in actions`);
     }
-    const response = await this.client.fetcher.fetchOrThrow(uri.toString(), {
+    return this.client.fetcher.fetchOrThrow(uri.toString(), {
       method: this.method,
       body,
       headers: {
         'Content-Type': this.contentType
       }
     });
-    const state = this.client.getStateForResponse(uri.toString(), response);
-    return state;
-
   }
 
   field(name: string): Field | undefined {

test/unit/state/hal-forms.ts

@@ -3,7 +3,7 @@ import { factory } from '../../../src/state/hal';
 import { Action, Client, Field } from '../../../src';
 import { HalFormsProperty } from 'hal-types';
 
-type CompareAction = Omit<Action, 'submit' | 'field'>;
+type CompareAction = Omit<Action, 'submit' | 'field' |  'submitFollow'>;
 
 describe('HAL forms', () => {