fix: enhance and tighten up Vercel adapter warnings (#9436)

- warn when prerender setting makes isr config useless
- don't show cron warning when everything's valid
- allow to set isr to false to clear isr config in leafs (else it's impossible to do so because config is merged at the top level)
- prefixed all warnings with "Warning:" which should help detect the Vercel log dashboard show these in condensed mode where only warnings/errors are shown
- prerender = 'auto' routes are now also excempt from further processing if we can determine that this is equal to prerender = true (because there are no dynamic routes)

---------

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

Author: dummdidumm

.changeset/forty-suns-listen.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': minor
+---
+
+feat: warn when prerender setting makes isr config useless

.changeset/polite-islands-glow.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: don't show cron warning when everything's valid

.changeset/tasty-weeks-rush.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: allow to set isr to false to clear isr config in leafs

packages/adapter-vercel/index.d.ts

@@ -32,23 +32,25 @@ export interface ServerlessConfig {
 	 * [Incremental Static Regeneration](https://vercel.com/docs/concepts/incremental-static-regeneration/overview) configuration.
 	 * Serverless only.
 	 */
-	isr?: {
-		/**
-		 * Expiration time (in seconds) before the cached asset will be re-generated by invoking the Serverless Function. Setting the value to `false` means it will never expire.
-		 */
-		expiration: number | false;
-		/**
-		 * Random token that can be provided in the URL to bypass the cached version of the asset, by requesting the asset
-		 * with a __prerender_bypass=<token> cookie.
-		 *
-		 * Making a `GET` or `HEAD` request with `x-prerender-revalidate: <token>` will force the asset to be re-validated.
-		 */
-		bypassToken?: string;
-		/**
-		 * List of query string parameter names that will be cached independently. If an empty array, query values are not considered for caching. If undefined each unique query value is cached independently
-		 */
-		allowQuery?: string[] | undefined;
-	};
+	isr?:
+		| {
+				/**
+				 * Expiration time (in seconds) before the cached asset will be re-generated by invoking the Serverless Function. Setting the value to `false` means it will never expire.
+				 */
+				expiration: number | false;
+				/**
+				 * Random token that can be provided in the URL to bypass the cached version of the asset, by requesting the asset
+				 * with a __prerender_bypass=<token> cookie.
+				 *
+				 * Making a `GET` or `HEAD` request with `x-prerender-revalidate: <token>` will force the asset to be re-validated.
+				 */
+				bypassToken?: string;
+				/**
+				 * List of query string parameter names that will be cached independently. If an empty array, query values are not considered for caching. If undefined each unique query value is cached independently
+				 */
+				allowQuery?: string[] | undefined;
+		  }
+		| false;
 }
 
 export interface EdgeConfig {

packages/adapter-vercel/index.js

@@ -153,13 +153,21 @@ const plugin = function (defaults = {}) {
 			/** @type {Map<import('@sveltejs/kit').RouteDefinition<import('.').Config>, { expiration: number | false, bypassToken: string | undefined, allowQuery: string[], group: number, passQuery: true }>} */
 			const isr_config = new Map();
 
+			/** @type {Set<string>} */
+			const ignored_isr = new Set();
+
 			// group routes by config
 			for (const route of builder.routes) {
-				if (route.prerender === true) continue;
+				const runtime = route.config?.runtime ?? defaults?.runtime ?? get_default_runtime();
+				const config = { runtime, ...defaults, ...route.config };
 
-				const pattern = route.pattern.toString();
+				if (is_prerendered(route)) {
+					if (config.isr) {
+						ignored_isr.add(route.id);
+					}
+					continue;
+				}
 
-				const runtime = route.config?.runtime ?? defaults?.runtime ?? get_default_runtime();
 				if (runtime && !VALID_RUNTIMES.includes(runtime)) {
 					throw new Error(
 						`Invalid runtime '${runtime}' for route ${
@@ -168,8 +176,6 @@ const plugin = function (defaults = {}) {
 					);
 				}
 
-				const config = { runtime, ...defaults, ...route.config };
-
 				if (config.isr) {
 					const directory = path.relative('.', builder.config.kit.files.routes + route.id);
 
@@ -197,6 +203,7 @@ const plugin = function (defaults = {}) {
 				const hash = hash_config(config);
 
 				// first, check there are no routes with incompatible configs that will be merged
+				const pattern = route.pattern.toString();
 				const existing = conflicts.get(pattern);
 				if (existing) {
 					if (existing.hash !== hash) {
@@ -219,6 +226,20 @@ const plugin = function (defaults = {}) {
 				group.routes.push(route);
 			}
 
+			if (ignored_isr.size) {
+				builder.log.warn(
+					`\nWarning: The following routes have an ISR config which is ignored because the route is prerendered:`
+				);
+
+				for (const ignored of ignored_isr) {
+					console.log(`    - ${ignored}`);
+				}
+
+				console.log(
+					'Either remove the "prerender" option from these routes to use ISR, or remove the ISR config.\n'
+				);
+			}
+
 			const singular = groups.size === 1;
 
 			for (const group of groups.values()) {
@@ -240,7 +261,7 @@ const plugin = function (defaults = {}) {
 			}
 
 			for (const route of builder.routes) {
-				if (route.prerender === true) continue;
+				if (is_prerendered(route)) continue;
 
 				const pattern = route.pattern.toString();
 
@@ -456,7 +477,7 @@ async function create_function_bundle(builder, entry, dir, config) {
 	if (resolution_failures.size > 0) {
 		const cwd = process.cwd();
 		builder.log.warn(
-			'The following modules failed to locate dependencies that may (or may not) be required for your app to work:'
+			'Warning: The following modules failed to locate dependencies that may (or may not) be required for your app to work:'
 		);
 
 		for (const [importer, modules] of resolution_failures) {
@@ -572,15 +593,26 @@ function validate_vercel_json(builder, vercel_config) {
 		unmatched_paths.push(path);
 	}
 
-	builder.log.warn(
-		`\nvercel.json defines cron tasks that use paths that do not correspond to an API route with a GET handler (ignore this if the request is handled in your \`handle\` hook):`
-	);
+	if (unmatched_paths.length) {
+		builder.log.warn(
+			`\nWarning: vercel.json defines cron tasks that use paths that do not correspond to an API route with a GET handler (ignore this if the request is handled in your \`handle\` hook):`
+		);
+
+		for (const path of unmatched_paths) {
+			console.log(`    - ${path}`);
+		}
 
-	for (const path of unmatched_paths) {
-		console.log(`    - ${path}`);
+		console.log('');
 	}
+}
 
-	console.log('');
+/** @param {import('@sveltejs/kit').RouteDefinition} route */
+function is_prerendered(route) {
+	return (
+		route.prerender === true ||
+		(route.prerender === 'auto' &&
+			route.segments.every((segment) => !segment.dynamic))
+	);
 }
 
 export default plugin;

packages/kit/types/index.d.ts

@@ -87,7 +87,7 @@ export interface Builder {
 	config: ValidatedConfig;
 	/** Information about prerendered pages and assets, if any. */
 	prerendered: Prerendered;
-	/** An array of dynamic (not prerendered) routes */
+	/** An array of all routes (including prerendered) */
 	routes: RouteDefinition[];
 
 	/**