add: config error if outDir is inside publicDir (#8152)

Co-authored-by: Nate Moore <natemoo-re@users.noreply.github.com>

.changeset/brown-numbers-prove.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Displays a new config error if `outDir` is placed within `publicDir`.

packages/astro/src/core/config/schema.ts

@@ -410,6 +410,8 @@ A future version of Astro will stop using the site pathname when producing <link
 		}
 
 		return config;
+	}).refine((obj) => !obj.outDir.toString().startsWith(obj.publicDir.toString()), {
+		message: '`outDir` must not be placed inside `publicDir` to prevent an infinite loop. Please adjust the directory configuration and try again'
 	});
 
 	return AstroConfigRelativeSchema;

packages/astro/test/units/config/config-validate.test.js

@@ -68,4 +68,10 @@ describe('Config Validation', () => {
 		).catch((err) => err);
 		expect(configError).to.be.not.instanceOf(Error);
 	});
+	it('Error when outDir is placed within publicDir', async () => {
+		const configError = await validateConfig({ outDir: './public/dist' }, process.cwd()).catch((err) => err);
+		expect(configError instanceof z.ZodError).to.equal(true);
+		expect(configError.errors[0].message).to.equal('`outDir` must not be placed inside `publicDir` to prevent an infinite loop. \
+Please adjust the directory configuration and try again')
+	});
 });