docs: fix remaining review issues

- Fix app.onError() missing path arg in error-handling.md
- Add missing HttpError import in error-handling.md
- Add missing define imports in WebSocket, subdomain, timing examples
- Standardize on `handler` (singular) for all export names
- Convert all untyped middleware to define.middleware()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju

docs/latest/advanced/error-handling.md

@@ -103,7 +103,9 @@ When an `HttpError` is thrown, Fresh catches it and invokes the error handler.
 You can check the status code in your error handler:
 
 ```ts main.ts
-app.onError((ctx) => {
+import { HttpError } from "fresh";
+
+app.onError("*", (ctx) => {
   if (ctx.error instanceof HttpError) {
     const status = ctx.error.status;
     return new Response("oops", { status });

docs/latest/concepts/data-fetching.md

@@ -20,7 +20,7 @@ interface Data {
   project: { name: string; stars: number };
 }
 
-export const handlers = define.handlers({
+export const handler = define.handlers({
   async GET(ctx) {
     const project = await db.projects.findOne(ctx.params.id);
     if (!project) {
@@ -30,7 +30,7 @@ export const handlers = define.handlers({
   },
 });
 
-export default define.page<typeof handlers>(({ data }) => {
+export default define.page<typeof handler>(({ data }) => {
   return (
     <div>
       <h1>{data.project.name}</h1>
@@ -40,8 +40,8 @@ export default define.page<typeof handlers>(({ data }) => {
 });
 ```
 
-The `define.page<typeof handlers>` generic links the handler's return type to
-the component's props, giving you full autocompletion on `data`.
+The `define.page<typeof handler>` generic links the handler's return type to the
+component's props, giving you full autocompletion on `data`.
 
 ## Setting response headers and status
 

docs/latest/examples/common-patterns.md

@@ -30,18 +30,20 @@ available in any downstream handler or component via `ctx.state.user`.
 Handle URL migrations with middleware:
 
 ```ts routes/_middleware.ts
+import { define } from "@/utils.ts";
+
 const REDIRECTS: Record<string, string> = {
   "/old-page": "/new-page",
   "/blog/old-slug": "/blog/new-slug",
 };
 
-export default function handler(ctx) {
+export default define.middleware((ctx) => {
   const redirect = REDIRECTS[ctx.url.pathname];
   if (redirect) {
     return ctx.redirect(redirect, 301);
   }
   return ctx.next();
-}
+});
 ```
 
 > [info]: `ctx.redirect()` includes protection against open redirect attacks.
@@ -55,7 +57,7 @@ Return different formats based on the `Accept` header:
 import { HttpError } from "fresh";
 import { define } from "@/utils.ts";
 
-export const handlers = define.handlers({
+export const handler = define.handlers({
   async GET(ctx) {
     const user = await db.users.find(ctx.params.id);
     if (!user) {
@@ -77,8 +79,9 @@ Use the `@std/http` cookie utilities:
 
 ```ts routes/_middleware.ts
 import { getCookies, setCookie } from "@std/http";
+import { define } from "@/utils.ts";
 
-export default async function handler(ctx) {
+export default define.middleware(async (ctx) => {
   const cookies = getCookies(ctx.req.headers);
   ctx.state.theme = cookies["theme"] ?? "light";
 
@@ -95,7 +98,7 @@ export default async function handler(ctx) {
   });
 
   return response;
-}
+});
 ```
 
 See [Session management](/docs/examples/session-management) for a complete
@@ -109,7 +112,7 @@ Access URL search params from the context:
 import { page } from "fresh";
 import { define } from "@/utils.ts";
 
-export const handlers = define.handlers({
+export const handler = define.handlers({
   GET(ctx) {
     const query = ctx.url.searchParams.get("q") ?? "";
     const pageNum = Number(ctx.url.searchParams.get("page") ?? "1");
@@ -121,15 +124,17 @@ export const handlers = define.handlers({
 
 ## Adding response headers
 
-Set custom headers in middleware or handlers:
+Set custom headers in middleware:
 
 ```ts routes/_middleware.ts
-export default async function handler(ctx) {
+import { define } from "@/utils.ts";
+
+export default define.middleware(async (ctx) => {
   const response = await ctx.next();
   response.headers.set("X-Frame-Options", "DENY");
   response.headers.set("X-Content-Type-Options", "nosniff");
   return response;
-}
+});
 ```
 
 Or set headers on a specific route using `page()`:
@@ -149,7 +154,7 @@ Return a streaming response from a handler:
 ```ts routes/api/stream.ts
 import { define } from "@/utils.ts";
 
-export const handlers = define.handlers({
+export const handler = define.handlers({
   GET() {
     const body = new ReadableStream({
       start(controller) {
@@ -172,7 +177,9 @@ export const handlers = define.handlers({
 Fresh runs on Deno, so you can upgrade HTTP connections to WebSockets directly:
 
 ```ts routes/api/ws.ts
-export const handlers = define.handlers({
+import { define } from "@/utils.ts";
+
+export const handler = define.handlers({
   GET(ctx) {
     const { socket, response } = Deno.upgradeWebSocket(ctx.req);
 
@@ -196,9 +203,11 @@ export const handlers = define.handlers({
 Use middleware with `URLPattern` to route based on subdomains:
 
 ```ts routes/_middleware.ts
+import { define } from "@/utils.ts";
+
 const SUBDOMAIN_PATTERN = new URLPattern({ hostname: ":sub.example.com" });
 
-export default async function handler(ctx) {
+export default define.middleware(async (ctx) => {
   const match = SUBDOMAIN_PATTERN.exec(ctx.req.url);
   if (match) {
     const sub = match.hostname.groups["sub"];
@@ -214,7 +223,7 @@ export default async function handler(ctx) {
     }
   }
   return ctx.next();
-}
+});
 ```
 
 ## Proxying requests
@@ -226,7 +235,7 @@ import { define } from "@/utils.ts";
 
 const UPSTREAM = "https://api.example.com";
 
-export const handlers = define.handlers({
+export const handler = define.handlers({
   async GET(ctx) {
     const url = new URL(ctx.params.path, UPSTREAM);
     url.search = ctx.url.search;
@@ -273,11 +282,13 @@ when `HeavyFeature` renders in the browser.
 Measure how long request processing takes:
 
 ```ts routes/_middleware.ts
-export default async function handler(ctx) {
+import { define } from "@/utils.ts";
+
+export default define.middleware(async (ctx) => {
   const start = performance.now();
   const response = await ctx.next();
   const duration = performance.now() - start;
   response.headers.set("Server-Timing", `total;dur=${duration.toFixed(1)}`);
   return response;
-}
+});
 ```