fix(compiler): type-check the emitted ssr binding array and share error handling across call sites

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

packages/compiler/src/codegen.ts

@@ -964,7 +964,7 @@ function apiBindingMap(ast: PageAst, sharedHelpers: string): Map<string, NamedDa
 }
 
 function ssrRuntimeSource(): string {
-  return `const __wrnexusHtmlEscapes = { "&": "&amp;", "<": "&lt;", ">": "&gt;", "\\"": "&quot;", "'": "&#39;" };
+  return `const __wrnexusHtmlEscapes: Record<string, string> = { "&": "&amp;", "<": "&lt;", ">": "&gt;", "\\"": "&quot;", "'": "&#39;" };
 function __wrnexusEscapeHtml(value: unknown): string {
   return String(value).replace(/[&<>"']/g, (ch) => __wrnexusHtmlEscapes[ch] ?? ch);
 }
@@ -1038,20 +1038,38 @@ async function __wrnexusCallApi(path: string, method: string, ctx: __WrnexusCont
   return type.includes("application/json") ? await res.json() : await res.text();
 }
 
+type __WrnexusApiCall = {
+  path: string;
+  method: string;
+  body: string;
+  helpers: string;
+  errorBody?: string;
+};
+
+type __WrnexusSsrBinding = __WrnexusApiCall & { marker: string };
+
+// Shared by every ssr api-binding consumption site (marker replacement,
+// #each loop consts, ...) so the narrow try/catch -- only active when the
+// block declared an error section -- cannot drift between call sites.
+async function __wrnexusResolveApiBinding(
+  binding: __WrnexusApiCall,
+  ctx: __WrnexusContext,
+): Promise<unknown> {
+  if (binding.errorBody) {
+    try {
+      const data = await __wrnexusCallApi(binding.path, binding.method, ctx);
+      return __wrnexusEvalData(data, binding.body, binding.helpers, ctx);
+    } catch (err) {
+      return __wrnexusEvalError(err, binding.errorBody, binding.helpers, ctx);
+    }
+  }
+  const data = await __wrnexusCallApi(binding.path, binding.method, ctx);
+  return __wrnexusEvalData(data, binding.body, binding.helpers, ctx);
+}
+
 async function __wrnexusRenderSsrBindings(html: string, ctx: __WrnexusContext): Promise<string> {
   for (const binding of __wrnexusSsrBindings) {
-    let value: unknown;
+    const value = await __wrnexusResolveApiBinding(binding, ctx);
-    if (binding.errorBody) {
-      try {
-        const data = await __wrnexusCallApi(binding.path, binding.method, ctx);
-        value = __wrnexusEvalData(data, binding.body, binding.helpers, ctx);
-      } catch (err) {
-        value = __wrnexusEvalError(err, binding.errorBody, binding.helpers, ctx);
-      }
-    } else {
-      const data = await __wrnexusCallApi(binding.path, binding.method, ctx);
-      value = __wrnexusEvalData(data, binding.body, binding.helpers, ctx);
-    }
     html = html.replace(binding.marker, __wrnexusEscapeHtml(value));
   }
   return html;
@@ -1560,8 +1578,11 @@ function generateInner(ast: PageAst): string {
     for (const [name, binding] of apiBindings) {
       if (binding.mode !== "ssr") continue;
       if (!lists.some((expr) => new RegExp(`\\b${name}\\b`).test(expr))) continue;
+      const errorBodyProp = binding.errorBody
+        ? `, errorBody: ${JSON.stringify(binding.errorBody)}`
+        : "";
       loopConsts.push(
-        `  const ${name} = __wrnexusEvalData(await __wrnexusCallApi(${JSON.stringify(binding.path)}, ${JSON.stringify(binding.method)}, ctx), ${JSON.stringify(binding.body)}, ${JSON.stringify(binding.helpers)}, ctx);`,
+        `  const ${name} = await __wrnexusResolveApiBinding({ path: ${JSON.stringify(binding.path)}, method: ${JSON.stringify(binding.method)}, body: ${JSON.stringify(binding.body)}, helpers: ${JSON.stringify(binding.helpers)}${errorBodyProp} }, ctx);`,
       );
     }
   }
@@ -1570,7 +1591,7 @@ function generateInner(ast: PageAst): string {
   if (needsSsrRuntime) {
     out.push(ssrRuntimeSource());
     out.push(
-      `const __wrnexusSsrBindings: Array<{ method: string; path: string; body: string; helpers: string; errorBody?: string }> = ${JSON.stringify(ssrBindings, null, 2)};`,
+      `const __wrnexusSsrBindings: __WrnexusSsrBinding[] = ${JSON.stringify(ssrBindings, null, 2)};`,
     );
     const decls = loopConsts.length > 0 ? loopConsts.join("\n") + "\n" : "";
     out.push(

packages/compiler/test/api-block-ssr.test.ts

@@ -1,7 +1,58 @@
-import { expect, test } from "bun:test";
+import { afterEach, expect, test } from "bun:test";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { parse } from "@wrnexus/syntax";
 import { generate } from "../src/codegen.ts";
 
+const ROOT_TSCONFIG = join(import.meta.dir, "../../../tsconfig.json").replace(/\\/g, "/");
+// The repo's own tsc, not a `bunx`-fetched one — `bunx tsc` can resolve an
+// unrelated TypeScript version that doesn't understand this repo's tsconfig
+// options (observed: it rejected `ignoreDeprecations: "6.0"` and couldn't
+// find the `bun` type-definition entry point), unlike `bun run typecheck`,
+// which uses this same local binary.
+const LOCAL_TSC = join(import.meta.dir, "../../../node_modules/.bin/tsc").replace(/\\/g, "/");
+// `types`/`typeRoots` in an extended tsconfig resolve relative to the config
+// file that's actually invoked (our temp one), not the base file — so the
+// ambient `bun` types need an explicit path back to the repo's node_modules.
+const TYPE_ROOTS = join(import.meta.dir, "../../../node_modules/@types").replace(/\\/g, "/");
+
+const roots: string[] = [];
+afterEach(() => {
+  for (const root of roots.splice(0)) rmSync(root, { recursive: true, force: true });
+});
+
+/**
+ * Runs the real TypeScript compiler over a generated server module. Proves
+ * the emitted `__wrnexusSsrBindings` annotation (and everything else in the
+ * module) actually type-checks — string-containment assertions alone can't
+ * catch a declared type that omits a field every emitted object literal has.
+ */
+function typecheckGenerated(source: string): { ok: boolean; output: string } {
+  const root = mkdtempSync(join(tmpdir(), "wrnexus-ssr-tsc-"));
+  roots.push(root);
+  const file = join(root, "page.ts");
+  writeFileSync(file, source);
+  // Reuse the repo's own tsconfig (paths, lib, types, jsx, ...) so this only
+  // checks the one file we care about instead of hand-duplicating the whole
+  // compiler configuration (and drifting from it over time).
+  writeFileSync(
+    join(root, "tsconfig.json"),
+    JSON.stringify({
+      extends: ROOT_TSCONFIG,
+      compilerOptions: { noEmit: true, typeRoots: [TYPE_ROOTS] },
+      include: ["page.ts"],
+    }),
+  );
+  const result = Bun.spawnSync([LOCAL_TSC, "--project", join(root, "tsconfig.json")], {
+    cwd: root,
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const output = `${result.stdout?.toString() ?? ""}${result.stderr?.toString() ?? ""}`;
+  return { ok: result.exitCode === 0, output };
+}
+
 function serverModule(inner: string): string {
   return generate(
     parse(`page Repro {
@@ -60,3 +111,95 @@ test("an ssr block without an error section emits no catch entry for that bindin
 
   expect(generated).not.toContain('"errorBody"');
 });
+
+test("tsc: a sectioned ssr block's generated module has no diagnostics", () => {
+  const generated = serverModule(`    api ssrUsers GET /api/users {
+      response {
+        return data.users.length
+      }
+      error {
+        return message + status + data
+      }
+    }`);
+
+  const { ok, output } = typecheckGenerated(generated);
+
+  expect(output.trim()).toBe("");
+  expect(ok).toBe(true);
+});
+
+test("an ssr block used in {#each} with an error section runs the error body on failure", async () => {
+  const generated = generate(
+    parse(`page Repro {
+  ssr {
+    api ssrUsers GET /api/users {
+      response {
+        return data.users
+      }
+      error {
+        return ["fallback"]
+      }
+    }
+  }
+
+  view { <main>{#each ssrUsers as u}<p>{u}</p>{/each}</main> }
+}
+`),
+  );
+
+  const root = mkdtempSync(join(tmpdir(), "wrnexus-ssr-each-"));
+  roots.push(root);
+  mkdirSync(root, { recursive: true });
+  const file = join(root, "page.ts");
+  writeFileSync(file, generated);
+
+  const mod = await import(`${file.replace(/\\/g, "/")}?t=${Date.now()}`);
+  const html = await mod.default({
+    req: { url: "http://localhost/", headers: new Headers() },
+    cookies: {},
+    session: {},
+    localStorage: {},
+    __wrnexusCallApi: async () => {
+      throw new Error("boom");
+    },
+  });
+
+  expect(html).toContain("fallback");
+});
+
+test("an ssr block used in {#each} without an error section still propagates a failure", async () => {
+  const generated = generate(
+    parse(`page Repro {
+  ssr {
+    api ssrUsers GET /api/users {
+      response {
+        return data.users
+      }
+    }
+  }
+
+  view { <main>{#each ssrUsers as u}<p>{u}</p>{/each}</main> }
+}
+`),
+  );
+
+  const root = mkdtempSync(join(tmpdir(), "wrnexus-ssr-each-propagate-"));
+  roots.push(root);
+  mkdirSync(root, { recursive: true });
+  const file = join(root, "page.ts");
+  writeFileSync(file, generated);
+
+  const mod = await import(`${file.replace(/\\/g, "/")}?t=${Date.now()}`);
+
+  await expect(
+    mod.default({
+      req: { url: "http://localhost/", headers: new Headers() },
+      cookies: {},
+      session: {},
+      localStorage: {},
+      __wrnexusCallApi: async () => {
+        throw new Error("boom");
+      },
+    }),
+  ).rejects.toThrow("boom");
+});