feat(compiler): resolve .tsx imports and tag them as islands

.wrn keeps resolution priority so existing components are unaffected
when a .tsx file shares their name.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/compiler/src/import-resolver.ts

@@ -11,6 +11,8 @@ export interface ImportResolverOptions {
 export interface ResolvedImport {
   declaration: StructuredImportDecl;
   resolved?: string;
+  /** `.tsx` imports are React islands, not `.wrn` components. */
+  kind?: "island";
   diagnostic?: { code: string; message: string; severity: "error" | "warning" };
 }
 
@@ -21,9 +23,11 @@ function candidates(path: string): string[] {
         path,
         `${path}.wrn`,
         `${path}.ts`,
+        `${path}.tsx`,
         `${path}.d.ts`,
         join(path, "index.wrn"),
         join(path, "index.ts"),
+        join(path, "index.tsx"),
       ];
 }
 
@@ -56,7 +60,12 @@ export function resolveWrnImport(
       return false;
     }
   });
-  if (found) return { declaration, resolved: realpathSync(found) };
+  if (found) {
+    const resolved = realpathSync(found);
+    return resolved.endsWith(".tsx")
+      ? { declaration, resolved, kind: "island" as const }
+      : { declaration, resolved };
+  }
   const severity = (options.mode ?? "compatible") === "explicit" ? "error" : "warning";
   return {
     declaration,

packages/compiler/test/island-resolution.test.ts

@@ -0,0 +1,64 @@
+import { expect, test } from "bun:test";
+import { mkdirSync, mkdtempSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { resolveWrnImport } from "../src/import-resolver.ts";
+
+function appWith(files: Record<string, string>) {
+  const root = mkdtempSync(join(tmpdir(), "wrnexus-island-"));
+  mkdirSync(join(root, "app"), { recursive: true });
+  for (const [name, contents] of Object.entries(files)) {
+    writeFileSync(join(root, "app", name), contents);
+  }
+  return root;
+}
+
+test("resolves a .tsx import and tags it as an island", () => {
+  const root = appWith({ "Chart.tsx": "export default function Chart() { return null; }" });
+  const result = resolveWrnImport(
+    { source: "./Chart", specifiers: [] } as any,
+    join(root, "app", "page.wrn"),
+    { appRoot: root },
+  );
+
+  expect(result.resolved).toContain("Chart.tsx");
+  expect(result.kind).toBe("island");
+});
+
+test("does not tag a .ts import as an island", () => {
+  const root = appWith({ "helper.ts": "export const value = 1;" });
+  const result = resolveWrnImport(
+    { source: "./helper", specifiers: [] } as any,
+    join(root, "app", "page.wrn"),
+    { appRoot: root },
+  );
+
+  expect(result.resolved).toContain("helper.ts");
+  expect(result.kind).toBeUndefined();
+});
+
+test("prefers .wrn over .tsx when both exist", () => {
+  const root = appWith({
+    "Widget.wrn": "<template></template>",
+    "Widget.tsx": "export default function Widget() { return null; }",
+  });
+  const result = resolveWrnImport(
+    { source: "./Widget", specifiers: [] } as any,
+    join(root, "app", "page.wrn"),
+    { appRoot: root },
+  );
+
+  expect(result.resolved).toContain("Widget.wrn");
+  expect(result.kind).toBeUndefined();
+});
+
+test("resolves an explicit .tsx extension as an island", () => {
+  const root = appWith({ "Chart.tsx": "export default function Chart() { return null; }" });
+  const result = resolveWrnImport(
+    { source: "./Chart.tsx", specifiers: [] } as any,
+    join(root, "app", "page.wrn"),
+    { appRoot: root },
+  );
+
+  expect(result.kind).toBe("island");
+});