feat: add customStaticWebAppConfig option (#28)

* allow extended SWA config

* handle overriding routes

* rename ExtendStaticWebAppConfig to CustomStaticWebAppConfig

* default custom config to empty object

* Add note about extending the generated SWA config

* Update docs, refactor, and format

* Tweak error messaging

Co-authored-by: Geoff Rich <[email protected]>

Author: biltongza

README.md

@@ -65,3 +65,47 @@ To run the CLI, install `@azure/static-web-apps-cli` and the [Azure Functions Co
 	}
 }
 ```
+
+## Options
+
+### customStaticWebAppConfig
+
+An object containing additional Azure SWA [configuration options](https://docs.microsoft.com/en-us/azure/static-web-apps/configuration). This will be merged with the `staticwebapp.config.json` generated by the adapter.
+
+Attempting to override the default catch-all route (`route: '*'`) or the `navigationFallback` options will throw an error, since they are critical for server-side rendering.
+
+**Note:** customizing this config (especially `routes`) has the potential to break how SvelteKit handles the request. Make sure to test any modifications thoroughly.
+
+```js
+import azure from 'svelte-adapter-azure-swa';
+
+export default {
+	kit: {
+		...
+		adapter: azure({
+			customStaticWebAppConfig: {
+				routes: [
+					{
+						route: '/login',
+						allowedRoles: ['admin']
+					}
+				],
+				globalHeaders: {
+					'X-Content-Type-Options': 'nosniff',
+					'X-Frame-Options': 'DENY',
+					'Content-Security-Policy': "default-src https: 'unsafe-eval' 'unsafe-inline'; object-src 'none'",
+				},
+				mimeTypes: {
+					'.json': 'text/json'
+				},
+				responseOverrides: {
+					'401': {
+						'redirect': '/login',
+						'statusCode': 302
+					}
+				}
+			}
+		})
+	}
+};
+```

index.d.ts

@@ -1,4 +1,8 @@
 import { Adapter } from '@sveltejs/kit';
+import { CustomStaticWebAppConfig } from './types/swa';
 
-declare function plugin(opts?: { debug?: boolean }): Adapter;
+declare function plugin(opts?: {
+	debug?: boolean;
+	customStaticWebAppConfig?: CustomStaticWebAppConfig;
+}): Adapter;
 export = plugin;

index.js

@@ -9,15 +9,38 @@ import esbuild from 'esbuild';
 
 const ssrFunctionRoute = '/api/__render';
 
+/**
+ * Validate the static web app configuration does not override the minimum config for the adapter to work correctly.
+ * @param config {import('./types/swa').CustomStaticWebAppConfig}
+ * */
+function validateCustomConfig(config) {
+	if (config) {
+		if ('navigationFallback' in config) {
+			throw new Error('customStaticWebAppConfig cannot override navigationFallback.');
+		}
+		if (config.routes && config.routes.find((route) => route.route === '*')) {
+			throw new Error(`customStaticWebAppConfig cannot override '*' route.`);
+		}
+	}
+}
+
 /** @type {import('.')} */
-export default function ({ debug = false } = {}) {
+export default function ({ debug = false, customStaticWebAppConfig = {} } = {}) {
 	return {
 		name: 'adapter-azure-swa',
 
 		async adapt(builder) {
+			validateCustomConfig(customStaticWebAppConfig);
+
+			if (!customStaticWebAppConfig.routes) {
+				customStaticWebAppConfig.routes = [];
+			}
+
 			/** @type {import('./types/swa').StaticWebAppConfig} */
 			const swaConfig = {
+				...customStaticWebAppConfig,
 				routes: [
+					...customStaticWebAppConfig.routes,
 					{
 						route: '*',
 						methods: ['POST', 'PUT', 'DELETE'],

types/swa.d.ts

@@ -2,8 +2,13 @@
 export interface StaticWebAppConfig {
 	routes?: Route[];
 	navigationFallback?: NavigationFallback;
+	globalHeaders?: Record<string, string>;
+	responseOverrides?: Record<OverridableResponseCodes, ResponseOverride>;
+	mimeTypes?: Record<string, string>;
 }
 
+export type CustomStaticWebAppConfig = Omit<StaticWebAppConfig, 'navigationFallback'>;
+
 export interface Route {
 	route: string;
 	methods?: HttpMethod[];
@@ -29,3 +34,11 @@ export type HttpMethod =
 	| 'OPTIONS'
 	| 'TRACE'
 	| 'PATCH';
+
+export interface ResponseOverride {
+	rewrite?: string;
+	statusCode?: number;
+	redirect?: string;
+}
+
+export type OverridableResponseCodes = '400' | '401' | '403' | '404';