Enhance custom configuration support

README.md

@@ -80,7 +80,13 @@ To run the CLI, install `@azure/static-web-apps-cli` and the [Azure Functions Co
 
 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.
+It can be useful to understand what's happening 'under the hood'. All requests for dynamic responses must be rewritten for the server-side rendering (SSR) function to render the page. If a request is not rewritten properly, bad things can happen. If the method requires a dynamic response (such as a `POST` request), SWA will respond with a `405` error. If the request method is `GET` but the file was not pre-rendered, SWA will use the `navigationFallback` rule to rewrite the request, which will fail if not set correctly.
+
+This adapter will ensure several routes are defined, along with `navigationFallback`, so dynamic rendering will occur correctly. If you define a catch-all wildcard route (`route: '/*'` or `route: '*'`), those settings will be used by every route this adapter creates. This will allow you to set a default `allowedRoles`, among other things. If you override the `rewrite` key of that route, you may force or prevent SSR from taking place.
+
+If you want to force a route to deliver only dynamically-generated responses, set `rewrite: 'ssr'` inside the route. Files that are not rendered by SvelteKit, such as static assets, may be inaccessible if you do this. Conversely, set `rewrite: undefined` to disable SSR in a route.
+
+If you want to prevent dynamic responses for requests in a route that has no dynamic content (such as an `/images` folder), you can set `exclude` in the `navigationFallback` rule to an array of routes that should not be dynamically handled. Read [Microsoft's documentation](https://learn.microsoft.com/en-us/azure/static-web-apps/configuration#fallback-routes) for a description of how `exclude` works.
 
 **Note:** customizing this config (especially `routes`) has the potential to break how SvelteKit handles the request. Make sure to test any modifications thoroughly.
 

index.d.ts

@@ -1,10 +1,10 @@
 import { Adapter } from '@sveltejs/kit';
-import { CustomStaticWebAppConfig } from './types/swa';
+import { StaticWebAppConfig } from './types/swa';
 import esbuild from 'esbuild';
 
 type Options = {
 	debug?: boolean;
-	customStaticWebAppConfig?: CustomStaticWebAppConfig;
+	customStaticWebAppConfig?: StaticWebAppConfig;
 	esbuildOptions?: Pick<esbuild.BuildOptions, 'external'>;
 };
 

index.js

@@ -8,29 +8,23 @@ 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.`);
-		}
-	}
-}
+// These are the methods that don't have to be SSR if they were pre-rendered.
+const staticMethods = ['GET', 'HEAD', 'OPTIONS'];
+// These are the methods that must always be SSR.
+const ssrMethods = ['CONNECT', 'DELETE', 'PATCH', 'POST', 'PUT', 'TRACE'];
+// This is the phrase that will be replaced with ssrFunctionRoute in custom configurations that use it.
+const ssrTrigger = 'ssr';
+// Default version of node to target
+const nodeVersion = 'node:16';
 
 /** @type {import('.').default} */
 export default function ({
 	debug = false,
 	customStaticWebAppConfig = {},
 	esbuildOptions = {}
 } = {}) {
-	return {
+	/** @type {import('@sveltejs/kit').Adapter} */
+	const adapter = {
 		name: 'adapter-azure-swa',
 
 		async adapt(builder) {
@@ -40,8 +34,6 @@ export default function ({
 				);
 			}
 
-			const swaConfig = generateConfig(customStaticWebAppConfig, builder.config.kit.appDir);
-
 			const tmp = builder.getBuildDirectory('azure-tmp');
 			const publish = 'build';
 			const staticDir = join(publish, 'static');
@@ -77,13 +69,25 @@ export default function ({
 
 			builder.copy(join(files, 'api'), apiDir);
 
+			const apiRuntime = (customStaticWebAppConfig.platform || {}).apiRuntime || nodeVersion;
+			const apiRuntimeParts = apiRuntime.match(/^node:(\d+)$/);
+			if (apiRuntimeParts === null) {
+				throw new Error(
+					`The configuration key platform.apiRuntime, if included, must be a supported Node version such as 'node:16'. It is currently '${apiRuntime}'.`
+				);
+			} else if (parseInt(apiRuntimeParts[1]) < 16) {
+				throw new Error(
+					`The minimum node version supported by SvelteKit is 16, please change configuration key platform.runTime from '${apiRuntime}' to a supported version like 'node:16' or remove it entirely.`
+				);
+			}
+
 			/** @type {BuildOptions} */
 			const default_options = {
 				entryPoints: [entry],
 				outfile: join(apiDir, 'index.js'),
 				bundle: true,
 				platform: 'node',
-				target: 'node16',
+				target: `node${apiRuntimeParts[1]}`,
 				sourcemap: 'linked',
 				external: esbuildOptions.external
 			};
@@ -99,59 +103,190 @@ export default function ({
 				// If the root was not pre-rendered, add a placeholder index.html
 				// Route all requests for the index to the SSR function
 				writeFileSync(`${staticDir}/index.html`, '');
-				swaConfig.routes.push(
-					{
-						route: '/index.html',
-						rewrite: ssrFunctionRoute
-					},
-					{
-						route: '/',
-						rewrite: ssrFunctionRoute
-					}
-				);
 			}
 
+			const swaConfig = generateConfig(builder, customStaticWebAppConfig);
+
 			writeFileSync(`${publish}/staticwebapp.config.json`, JSON.stringify(swaConfig));
 		}
 	};
+	return adapter;
 }
 
 /**
- * @param {import('./types/swa').CustomStaticWebAppConfig} customStaticWebAppConfig
- * @param {string} appDir
+ * @param {import('@sveltejs/kit').Builder} builder A reference to the SvelteKit builder
+ * @param {import('./types/swa').StaticWebAppConfig} customStaticWebAppConfig Custom configuration
  * @returns {import('./types/swa').StaticWebAppConfig}
  */
-export function generateConfig(customStaticWebAppConfig, appDir) {
-	validateCustomConfig(customStaticWebAppConfig);
-
-	if (!customStaticWebAppConfig.routes) {
-		customStaticWebAppConfig.routes = [];
-	}
-
+export function generateConfig(builder, customStaticWebAppConfig = {}) {
+	builder.log.minor(`Generating static web app config...`);
 	/** @type {import('./types/swa').StaticWebAppConfig} */
 	const swaConfig = {
 		...customStaticWebAppConfig,
-		routes: [
-			...customStaticWebAppConfig.routes,
-			{
-				route: '*',
-				methods: ['POST', 'PUT', 'DELETE'],
-				rewrite: ssrFunctionRoute
-			},
-			{
-				route: `/${appDir}/immutable/*`,
-				headers: {
-					'cache-control': 'public, immutable, max-age=31536000'
-				}
-			}
-		],
 		navigationFallback: {
-			rewrite: ssrFunctionRoute
+			rewrite: ssrFunctionRoute,
+			...customStaticWebAppConfig.navigationFallback
 		},
 		platform: {
-			apiRuntime: 'node:16'
-		}
+			apiRuntime: nodeVersion,
+			...customStaticWebAppConfig.platform
+		},
+		routes: []
+	};
+
+	if (swaConfig.navigationFallback.rewrite === ssrTrigger) {
+		swaConfig.navigationFallback.rewrite = ssrFunctionRoute;
+	}
+
+	/** @type {Record<string,import('./types/swa').HttpMethod[]>} */
+	let handledRoutes = {
+		'*': [],
+		'/': [],
+		'/index.html': []
+	};
+	/** @type {import('./types/swa').Route} */
+	let wildcardRoute = {
+		route: '*'
 	};
 
+	for (const route of customStaticWebAppConfig.routes || []) {
+		if (route.route === undefined || !route.route.length) {
+			throw new Error(
+				'A route pattern is required for each route. https://learn.microsoft.com/en-us/azure/static-web-apps/configuration#routes'
+			);
+		}
+		route.methods = route.methods || [...staticMethods, ...ssrMethods];
+		if (handledRoutes[route.route] && handledRoutes[route.route].some((i) => methods.includes(i))) {
+			throw new Error(
+				'There is a route that conflicts with another route. https://learn.microsoft.com/en-us/azure/static-web-apps/configuration#routes'
+			);
+		}
+		handledRoutes[route.route] = [...(handledRoutes[route.route] || []), ...route.methods];
+		if (route.rewrite === ssrTrigger) {
+			route.rewrite = ssrFunctionRoute;
+		}
+		if (['/*', '*'].includes(route.route)) {
+			route.route = '*';
+			wildcardRoute = route;
+		}
+		if (route.methods.length === staticMethods.length + ssrMethods.length) {
+			// Either method isn't specified in this route, or all methods are.
+			if (['/index.html', '/'].includes(route.route) && !builder.prerendered.paths.includes('/')) {
+				// The root route must be fully SSR because it was not rendered. No need to split the route.
+				swaConfig.routes.push({
+					rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+					...route
+				});
+			} else {
+				// This route catches all methods, but we don't want to force SSR for all methods, so will split the rule.
+				swaConfig.routes.push({
+					...route,
+					methods: staticMethods
+				});
+				swaConfig.routes.push({
+					rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+					...route,
+					methods: ssrMethods
+				});
+			}
+		} else if (route.methods.some((r) => ssrMethods.includes(r))) {
+			const routeSSRMethods = methods.filter((m) => ssrMethods.includes(m));
+			if (routeSSRMethods.length === methods.length) {
+				// This route is only for SSR methods, so we'll rewrite the single rule.
+				swaConfig.routes.push({
+					rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+					...route
+				});
+			} else {
+				if (
+					['/index.html', '/'].includes(route.route) &&
+					!builder.prerendered.paths.includes('/')
+				) {
+					// This special route must be SSR because it was not pre-rendered.
+					swaConfig.routes.push({
+						rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+						...route
+					});
+				} else {
+					// This route is for some methods that must be SSR, but not all. We'll split it.
+					swaConfig.routes.push({
+						rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+						...route,
+						methods: routeSSRMethods
+					});
+					swaConfig.routes.push({
+						...route,
+						methods: methods.filter((m) => staticMethods.includes(m))
+					});
+				}
+			}
+		} else {
+			if (['/index.html', '/'].includes(route.route) && !builder.prerendered.paths.includes('/')) {
+				// This special route must be SSR because it was not pre-rendered.
+				swaConfig.routes.push({
+					rewrite: route.redirect ? route.rewrite : ssrFunctionRoute,
+					...route
+				});
+			} else {
+				// None of the methods in this route must be SSR, so accept it as-is.
+				swaConfig.routes.push({ ...route });
+			}
+		}
+	}
+
+	// Make sure the wildcard is there for each SSR method.
+	const missingWildcardMethods = ssrMethods.filter(
+		(i) => !(wildcardRoute.methods || []).includes(i)
+	);
+	if (missingWildcardMethods.length > 0) {
+		handledRoutes['*'] = missingWildcardMethods;
+		swaConfig.routes.push({
+			rewrite: ssrFunctionRoute,
+			...wildcardRoute,
+			methods: missingWildcardMethods
+		});
+	}
+
+	// Make sure the fallback rewrite matches the custom config or wildcard route, if present.
+	if ((customStaticWebAppConfig.navigationFallback || []).hasOwnProperty('rewrite')) {
+		swaConfig.navigationFallback.rewrite = customStaticWebAppConfig.navigationFallback.rewrite;
+	} else if (wildcardRoute.hasOwnProperty('rewrite')) {
+		swaConfig.navigationFallback.rewrite = wildcardRoute.rewrite;
+	}
+
+	handledRoutes[`/${builder.config.kit.appDir}/immutable/*`] = [...staticMethods, ...ssrMethods];
+	swaConfig.routes.push({
+		...wildcardRoute,
+		route: `/${builder.config.kit.appDir}/immutable/*`,
+		headers: {
+			'cache-control': 'public, immutable, max-age=31536000'
+		},
+		methods: undefined
+	});
+	if (!builder.prerendered.paths.includes('/')) {
+		if (!staticMethods.every((i) => handledRoutes['/index.html'].includes(i))) {
+			swaConfig.routes.push({
+				rewrite: wildcardRoute.redirect ? wildcardRoute.rewrite : ssrFunctionRoute,
+				...wildcardRoute,
+				route: '/index.html',
+				methods: undefined
+			});
+		}
+		if (!staticMethods.every((i) => handledRoutes['/'].includes(i))) {
+			swaConfig.routes.push({
+				rewrite: wildcardRoute.redirect ? wildcardRoute.rewrite : ssrFunctionRoute,
+				...wildcardRoute,
+				route: '/',
+				methods: undefined
+			});
+		}
+	}
+
+	if (swaConfig.navigationFallback.rewrite !== ssrFunctionRoute) {
+		builder.log.warn(
+			`Custom configuration has navigationFallback.rewrite set to a value other than '${ssrTrigger}'. SSR will fail unless a route specifies it.`
+		);
+	}
+
 	return swaConfig;
 }