test: configure vite resolve.alias for component paths

Author: metonym

vite.config.ts

@@ -1,14 +1,60 @@
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
 import { svelte, vitePreprocess } from "@sveltejs/vite-plugin-svelte";
 import { optimizeImports } from "carbon-preprocess-svelte";
 import { defineConfig } from "vitest/config";
+import pkg from "./package.json";
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+/**
+ * Generates Vite aliases from package.json exports for component subpath imports.
+ * Resolves imports like `carbon-components-svelte/Theme/Theme.svelte` to
+ * `./src/Theme/Theme.svelte` since these subpaths aren't in package.json
+ * exports and Vite needs runtime resolution (tsconfig only handles types).
+ */
+function generateAliasesFromExports() {
+  const aliases: Record<string, string> = {};
+  const exports = pkg.exports;
+
+  const srcSvelteExport = exports["./src/*.svelte"];
+  if (!srcSvelteExport) return aliases;
+
+  const srcDir = path.resolve(__dirname, "./src");
+  if (!fs.existsSync(srcDir)) return aliases;
+
+  function scanDirectory(dir: string, basePath: string = "") {
+    const entries = fs.readdirSync(dir, { withFileTypes: true });
+
+    for (const entry of entries) {
+      const fullPath = path.join(dir, entry.name);
+      const relativePath = path.join(basePath, entry.name);
+
+      if (entry.isDirectory()) {
+        scanDirectory(fullPath, relativePath);
+      } else if (entry.isFile() && entry.name.endsWith(".svelte")) {
+        const importPath = relativePath;
+        const aliasKey = `${pkg.name}/${importPath}`;
+        aliases[aliasKey] = path.resolve(__dirname, "./src", importPath);
+      }
+    }
+  }
+
+  scanDirectory(srcDir);
+  return aliases;
+}
 
 export default defineConfig({
   root: "./tests",
   plugins: [svelte({ preprocess: [vitePreprocess(), optimizeImports()] })],
   optimizeDeps: {
     exclude: ["carbon-components-svelte", "carbon-icons-svelte"],
   },
-  resolve: { conditions: ["browser"] },
+  resolve: {
+    conditions: ["browser"],
+    alias: generateAliasesFromExports(),
+  },
   test: {
     globals: true,
     environment: "jsdom",