Treat Props as used when Astro.props is referenced (resolve #1629)

Author: webpro

packages/knip/fixtures/plugins/astro/knip.ts

@@ -1,5 +1,6 @@
 export default {
   ignore: '.astro/types.d.ts',
+  ignoreExportsUsedInFile: true,
   compilers: {
     css: (text: string) => [...text.matchAll(/(?<=@)import[^;]+/g)].join('\n'),
   },

packages/knip/fixtures/plugins/astro/src/components/FormattedDate.astro

@@ -1,5 +1,5 @@
 ---
-interface Props {
+export interface Props {
   date: Date;
 }
 

packages/knip/src/plugins/astro/compiler.ts

@@ -1,10 +1,16 @@
 import { frontmatterMatcher, scriptBodies } from '../../compilers/compilers.ts';
 
+const propsDeclMatcher = /(?:^|[\s;])(?:interface|type)\s+Props\b/;
+
 const compiler = (text: string, path: string) => {
   const scripts = [];
 
   const frontmatter = text.match(frontmatterMatcher);
-  if (frontmatter?.[1]) scripts.push(frontmatter[1]);
+  if (frontmatter?.[1]) {
+    let fm = frontmatter[1];
+    if (propsDeclMatcher.test(fm) && text.includes('Astro.props')) fm += '\ntype __knip_astro_props = Props;';
+    scripts.push(fm);
+  }
 
   const scriptContent = scriptBodies(text, path);
   if (scriptContent) scripts.push(scriptContent);