feat(cli): generate type assertions for api blocks

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

packages/cli/src/types.ts

@@ -4,7 +4,7 @@ import { buildRouter, createRouteManifest, nameRoutes } from "@wrnexus/router";
 // Keep the CLI checker sourced from the package contract so typecheck fixes are
 // included in each published CLI bundle.
 import { checkWrnFile, type WrnTypeDiagnostic } from "@wrnexus/typecheck";
-import { parse } from "@wrnexus/syntax";
+import { parse, type PageAst } from "@wrnexus/syntax";
 import { generate, generateTargets } from "@wrnexus/compiler";
 import { regenerateRoutes } from "./routes.ts";
 import { loadAppConfig } from "@wrnexus/styles";
@@ -99,6 +99,42 @@ function writePluginArtifacts(root: string, contributions?: PluginContributions)
   );
 }
 
+/**
+ * Type assertions for sectioned api blocks.
+ *
+ * Enforcement lives here rather than in the compiler because this file is under
+ * `app/` and is therefore compiled by the project's own tsc, while generated
+ * build artifacts are not type-checked at all.
+ */
+function apiBlockAssertions(pages: { path: string; ast: PageAst }[], apiContracts: string): string {
+  const lines: string[] = [];
+
+  for (const page of pages) {
+    for (const block of page.ast.dataApis) {
+      if (!block.sections) continue;
+
+      if (!apiContracts.includes(JSON.stringify(block.path))) {
+        console.warn(
+          `[wrnexus] api block "${block.name}" targets ${block.path}, which has no defineEndpoint contract — its declared types are not checked.`,
+        );
+      }
+
+      const fields = [...block.sections.parameters, ...block.sections.body];
+      const shape = fields.length
+        ? `{ ${fields.map((f) => `${f.name}${f.optional ? "?" : ""}: ${f.type}`).join("; ")} }`
+        : "Record<string, never>";
+
+      lines.push(
+        `  type __wrn_api_check_${block.name} = __wrn_expect_true<AssertAssignable<${shape}, ApiInput<${JSON.stringify(
+          block.path,
+        )}, ${JSON.stringify(block.method)}>>>;`,
+      );
+    }
+  }
+
+  return lines.join("\n");
+}
+
 export function generateApplicationTypes(
   appRoot: string,
   pluginContributions?: PluginContributions,
@@ -145,6 +181,10 @@ export function generateApplicationTypes(
       return `    ${JSON.stringify(component.name)}: { props: ${props ? `{ ${props} }` : "Record<string, never>"}; outputs: ${outputs ? `{ ${outputs} }` : "Record<string, never>"} };`;
     })
     .join("\n");
+  const pageAsts = files(app, (path) => extname(path) === ".wrn").map((file) => ({
+    path: file,
+    ast: parse(readFileSync(file, "utf8")),
+  }));
   const typeDir = join(app, "types");
   const apiContracts = router.api
     .map((route) => {
@@ -218,6 +258,11 @@ declare namespace WRNexusGenerated {
   ${generatedContractMap("RealtimeMessages", realtimeContracts)}
   ${generatedContractMap("QueuePayloads", queueContracts)}
   type ApplicationConfig = ${configFile ? `(typeof import(${typeImport(typeDir, configFile)}))["default"]` : "Record<string, never>"};
+  type AssertAssignable<Actual, Expected> = [Actual] extends [Expected] ? true : false;
+  type __wrn_expect_true<T extends true> = T;
+  type ApiInput<P extends ApiRoute, M> = ApiContracts[P][M]["input"];
+  type ApiOutput<P extends ApiRoute, M> = ApiContracts[P][M]["output"];
+${apiBlockAssertions(pageAsts, apiContracts)}
 }
 `;
   mkdirSync(typeDir, { recursive: true });