Make Astro.url conform to build.format during the build (#4352)

* Make Astro.url conform to build.format during the build

* Adding a changeset

* Better implementation

* fix some stuff that tests failed on

* Add docs

* Change to minor

* account for empty path

.changeset/beige-deers-travel.md

@@ -0,0 +1,5 @@
+---
+'astro': minor
+---
+
+Make Astro.url match the build.format configuration during the build

packages/astro/src/@types/astro.ts

@@ -428,7 +428,7 @@ export interface AstroUserConfig {
 	 * @name trailingSlash
 	 * @type {('always' | 'never' | 'ignore')}
 	 * @default `'ignore'`
-	 * @see buildOptions.pageUrlFormat
+	 * @see build.format
 	 * @description
 	 *
 	 * Set the route matching behavior of the dev server. Choose from the following options:
@@ -517,6 +517,13 @@ export interface AstroUserConfig {
 		 *   }
 		 * }
 		 * ```
+		 * 
+		 * #### Effect on Astro.url
+		 * Setting `build.format` controls what `Astro.url` is set to during the build. When it is:
+     * - `directory` - The `Astro.url.pathname` will include a trailing slash to mimic folder behavior; ie `/foo/`.
+     * - `file` - The `Astro.url.pathname` will include `.html`; ie `/foo.html`. 
+     *
+     * This means that when you create relative URLs using `new URL('./relative', Astro.url)`, you will get consistent behavior between dev and build.
 		 */
 		format?: 'file' | 'directory';
 	};

packages/astro/src/core/build/generate.ts

@@ -8,6 +8,7 @@ import type {
 	AstroConfig,
 	ComponentInstance,
 	EndpointHandler,
+	RouteType,
 	SSRLoadedRenderer,
 } from '../../@types/astro';
 import type { BuildInternals } from '../../core/build/internal.js';
@@ -243,6 +244,27 @@ function addPageName(pathname: string, opts: StaticBuildOptions): void {
 	opts.pageNames.push(pathname.replace(/^\//, ''));
 }
 
+function getUrlForPath(pathname: string, base: string, origin: string, format: 'directory' | 'file', routeType: RouteType): URL {
+	/**
+	 * Examples:
+	 * pathname: /, /foo
+	 * base: /
+	 */
+	const ending = format === 'directory' ? '/' : '.html';
+	let buildPathname: string;
+	if(pathname === '/' || pathname === '') {
+		buildPathname = base;
+	} else if(routeType === 'endpoint') {
+		const buildPathRelative = removeLeadingForwardSlash(pathname);
+		buildPathname = base + buildPathRelative;
+	} else {
+		const buildPathRelative = removeTrailingForwardSlash(removeLeadingForwardSlash(pathname)) + ending;
+		buildPathname = base + buildPathRelative;
+	}
+	const url = new URL(buildPathname, origin);
+	return url;
+}
+
 async function generatePath(
 	pathname: string,
 	opts: StaticBuildOptions,
@@ -290,7 +312,8 @@ async function generatePath(
 	}
 
 	const ssr = opts.astroConfig.output === 'server';
-	const url = new URL(opts.astroConfig.base + removeLeadingForwardSlash(pathname), origin);
+	const url = getUrlForPath(pathname, opts.astroConfig.base, origin,
+		opts.astroConfig.build.format, pageData.route.type);
 	const options: RenderOptions = {
 		adapterName: undefined,
 		links,

packages/astro/test/astro-get-static-paths.test.js

@@ -169,6 +169,6 @@ describe('getStaticPaths - Astro.url', () => {
 		const html = await fixture.readFile('/food/tacos/index.html');
 		const $ = cheerio.load(html);
 
-		expect($('#url').text()).to.equal('/food/tacos');
+		expect($('#url').text()).to.equal('/food/tacos/');
 	});
 });

packages/astro/test/fixtures/page-format/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@test/page-format",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*"
+  }
+}

packages/astro/test/fixtures/page-format/src/pages/nested/page.astro

@@ -0,0 +1,4 @@
+---
+const another = new URL('./another/', Astro.url);
+---
+<a id="another" href={another.pathname}></a>

packages/astro/test/page-format.test.js

@@ -0,0 +1,52 @@
+import { expect } from 'chai';
+import * as cheerio from 'cheerio';
+import { loadFixture } from './test-utils.js';
+
+describe('build.format', () => {
+  describe('directory', () => {
+    /** @type {import('./test-utils').Fixture} */
+    let fixture;
+    before(async () => {
+      fixture = await loadFixture({
+        root: './fixtures/page-format/',
+      });
+    });
+
+    describe('Build', () => {
+      before(async () => {
+        await fixture.build();
+      });
+
+      it('relative urls created point to sibling folders', async () => {
+        let html = await fixture.readFile('/nested/page/index.html');
+        let $ = cheerio.load(html);
+        expect($('#another').attr('href')).to.equal('/nested/page/another/');
+      });
+    });
+  });
+
+	describe('file', () => {
+    /** @type {import('./test-utils').Fixture} */
+    let fixture;
+    before(async () => {
+      fixture = await loadFixture({
+        root: './fixtures/page-format/',
+				build: {
+					format: 'file',
+				},
+      });
+    });
+
+    describe('Build', () => {
+      before(async () => {
+        await fixture.build();
+      });
+
+      it('relative urls created point to sibling folders', async () => {
+        let html = await fixture.readFile('/nested/page.html');
+        let $ = cheerio.load(html);
+        expect($('#another').attr('href')).to.equal('/nested/another/');
+      });
+    });
+  });
+});