fix: allow strings for ISR expiration, parse input (#14691)

* fix: allow strings for ISR expiration, parse input

* improvements

Author: elliott-with-the-longest-name-on-github

.changeset/two-humans-thank.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': minor
+---
+
+feat: parse isr.expiration, allowing it to be a string

packages/adapter-vercel/index.d.ts

@@ -39,7 +39,7 @@ export interface ServerlessConfig {
 				/**
 				 * 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;
+				expiration: number | string | 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.

packages/adapter-vercel/index.js

@@ -5,7 +5,7 @@ import process from 'node:process';
 import { fileURLToPath } from 'node:url';
 import { nodeFileTrace } from '@vercel/nft';
 import esbuild from 'esbuild';
-import { get_pathname, pattern_to_src } from './utils.js';
+import { get_pathname, parse_isr_expiration, pattern_to_src } from './utils.js';
 import { VERSION } from '@sveltejs/kit';
 
 /**
@@ -433,7 +433,11 @@ const plugin = function (defaults = {}) {
 					fs.symlinkSync(`../${relative}`, `${base}/__data.json.func`);
 
 					const pathname = get_pathname(route);
-					const json = JSON.stringify(isr, null, '\t');
+					const json = JSON.stringify(
+						{ ...isr, expiration: parse_isr_expiration(isr.expiration, route.id) },
+						null,
+						'\t'
+					);
 
 					write(`${base}.prerender-config.json`, json);
 					write(`${base}/__data.json.prerender-config.json`, json);

packages/adapter-vercel/test/utils.spec.js

@@ -1,5 +1,5 @@
-import { assert, test } from 'vitest';
-import { get_pathname, pattern_to_src } from '../utils.js';
+import { assert, test, describe } from 'vitest';
+import { get_pathname, parse_isr_expiration, pattern_to_src } from '../utils.js';
 
 // workaround so that TypeScript doesn't follow that import which makes it pick up that file and then error on missing import aliases
 const { parse_route_id } = await import('../../kit/src/' + 'utils/routing.js');
@@ -130,3 +130,44 @@ test('pattern_to_src for route with rest parameter', () => {
 test('pattern_to_src for route with rest parameter in the middle', () => {
 	run_pattern_to_src_test('/foo/[...bar]/baz', '^/foo(/[^]*)?/baz/?');
 });
+
+describe('parse_isr_expiration', () => {
+	test.each(
+		/** @type {const} */ ([
+			[1, 1],
+			['1', 1],
+			[false, false],
+			['false', false]
+		])
+	)('works for valid inputs ($0)', (input, output) => {
+		const result = parse_isr_expiration(input, '/isr');
+		assert.equal(result, output);
+	});
+
+	test('does not allow floats', () => {
+		assert.throws(() => parse_isr_expiration(1.5, '/isr'), /should be an integer, in \/isr/);
+	});
+
+	test('does not allow `true`', () => {
+		const val = /** @type {false} */ (true);
+		assert.throws(() => parse_isr_expiration(val, '/isr'), /should be an integer, in \/isr/);
+	});
+
+	test('does not allow negative numbers', () => {
+		assert.throws(() => parse_isr_expiration(-1, '/isr'), /should be non-negative, in \/isr/);
+	});
+
+	test('does not allow strings that do not parse to valid numbers', () => {
+		assert.throws(
+			() => parse_isr_expiration('foo', '/isr'),
+			/value was a string but could not be parsed as an integer, in \/isr/
+		);
+	});
+
+	test('does not allow strings that parse to floats', () => {
+		assert.throws(
+			() => parse_isr_expiration('1.1', '/isr'),
+			/value was a string but could not be parsed as an integer, in \/isr/
+		);
+	});
+});

packages/adapter-vercel/utils.js

@@ -67,3 +67,42 @@ export function pattern_to_src(pattern) {
 
 	return src;
 }
+
+const integer = /^\d+$/;
+
+/**
+ * @param {false | string | number} value
+ * @param {string} route_id
+ * @returns {number | false}
+ */
+export function parse_isr_expiration(value, route_id) {
+	if (value === false || value === 'false') return false; // 1 year
+
+	/** @param {string} desc */
+	const err = (desc) => {
+		throw new Error(
+			`Invalid isr.expiration value: ${JSON.stringify(value)} (${desc}, in ${route_id})`
+		);
+	};
+
+	let parsed;
+	if (typeof value === 'string') {
+		if (!integer.test(value)) {
+			err('value was a string but could not be parsed as an integer');
+		}
+		parsed = Number.parseInt(value, 10);
+	} else {
+		if (!Number.isInteger(value)) {
+			err('should be an integer');
+		}
+		parsed = value;
+	}
+
+	if (Number.isNaN(parsed)) {
+		err('should be a number');
+	}
+	if (parsed < 0) {
+		err('should be non-negative');
+	}
+	return parsed;
+}