MOBILE-3106 core: Use GET as fallback in get public config

src/classes/site.ts

@@ -21,7 +21,7 @@ import { CoreDbProvider } from '@providers/db';
 import { CoreEventsProvider } from '@providers/events';
 import { CoreFileProvider } from '@providers/file';
 import { CoreLoggerProvider } from '@providers/logger';
-import { CoreWSProvider, CoreWSPreSets, CoreWSFileUploadOptions } from '@providers/ws';
+import { CoreWSProvider, CoreWSPreSets, CoreWSFileUploadOptions, CoreWSAjaxPreSets } from '@providers/ws';
 import { CoreDomUtilsProvider } from '@providers/utils/dom';
 import { CoreTextUtilsProvider } from '@providers/utils/text';
 import { CoreTimeUtilsProvider } from '@providers/utils/time';
@@ -1432,7 +1432,22 @@ export class CoreSite {
      * @return {Promise<any>} Promise resolved with public config. Rejected with an object if error, see CoreWSProvider.callAjax.
      */
     getPublicConfig(): Promise<any> {
-        return this.wsProvider.callAjax('tool_mobile_get_public_config', {}, { siteUrl: this.siteUrl }).then((config) => {
+        const preSets: CoreWSAjaxPreSets = {
+            siteUrl: this.siteUrl
+        };
+
+        return this.wsProvider.callAjax('tool_mobile_get_public_config', {}, preSets).catch((error) => {
+
+            if ((!this.getInfo() || this.isVersionGreaterEqualThan('3.8')) && error && error.errorcode == 'codingerror') {
+                // This error probably means that there is a redirect in the site. Try to use a GET request.
+                preSets.noLogin = true;
+                preSets.useGet = true;
+
+                return this.wsProvider.callAjax('tool_mobile_get_public_config', {}, preSets);
+            }
+
+            return Promise.reject(error);
+        }).then((config) => {
             // Use the wwwroot returned by the server.
             if (config.httpswwwroot) {
                 this.siteUrl = config.httpswwwroot;

src/providers/ws.ts

@@ -76,6 +76,18 @@ export interface CoreWSAjaxPreSets {
      * @type {boolean}
      */
     responseExpected?: boolean;
+
+    /**
+     * Whether to use the no-login endpoint instead of the normal one. Use it for requests that don't require authentication.
+     * @type {boolean}
+     */
+    noLogin?: boolean;
+
+    /**
+     * Whether to send the parameters via GET. Only if noLogin is true.
+     * @type {boolean}
+     */
+    useGet?: boolean;
 }
 
 /**
@@ -215,8 +227,7 @@ export class CoreWSProvider {
      *                                 - available: 0 if unknown, 1 if available, -1 if not available.
      */
     callAjax(method: string, data: any, preSets: CoreWSAjaxPreSets): Promise<any> {
-        let siteUrl,
+        let promise;
-            ajaxData;
 
         if (typeof preSets.siteUrl == 'undefined') {
             return rejectWithError(this.createFakeWSError('core.unexpectederror', true));
@@ -228,17 +239,24 @@ export class CoreWSProvider {
             preSets.responseExpected = true;
         }
 
-        ajaxData = [{
+        const script = preSets.noLogin ? 'service-nologin.php' : 'service.php',
+            ajaxData = JSON.stringify([{
                 index: 0,
                 methodname: method,
                 args: this.convertValuesToString(data)
-        }];
+            }]);
 
         // The info= parameter has no function. It is just to help with debugging.
         // We call it info to match the parameter name use by Moodle's AMD ajax module.
-        siteUrl = preSets.siteUrl + '/lib/ajax/service.php?info=' + method;
+        let siteUrl = preSets.siteUrl + '/lib/ajax/' + script + '?info=' + method;
 
-        const promise = this.http.post(siteUrl, JSON.stringify(ajaxData)).timeout(CoreConstants.WS_TIMEOUT).toPromise();
+        if (preSets.noLogin && preSets.useGet) {
+            // Send params using GET.
+            siteUrl += '&args=' + encodeURIComponent(ajaxData);
+            promise = this.http.get(siteUrl).timeout(CoreConstants.WS_TIMEOUT).toPromise();
+        } else {
+            promise = this.http.post(siteUrl, ajaxData).timeout(CoreConstants.WS_TIMEOUT).toPromise();
+        }
 
         return promise.then((data: any) => {
             // Some moodle web services return null.