fix(core): support method handler on _error, _404 and _500 routes (#2955)

This PR adds support for using method handlers in `_error`, `_404` and
`_500` files.

Fixes #2953

Author: marvinhagemeister

src/plugins/fs_routes/mod.ts

@@ -258,7 +258,16 @@ export async function fsRoutes<State>(
           ? undefined
           : typeof handlers === "function"
           ? handlers
-          : undefined; // FIXME: Method handler
+          : ((ctx) => {
+            const { method } = ctx.req;
+            if (!Array.isArray(handlers)) {
+              const maybeFn = handlers[method as Method];
+              if (maybeFn !== undefined) {
+                return maybeFn(ctx);
+              }
+            }
+            return ctx.next();
+          }) as HandlerFn<unknown, State>;
         const errorComponents = components.slice();
         if (mod.component !== null) {
           errorComponents.push(mod.component);
@@ -285,7 +294,16 @@ export async function fsRoutes<State>(
           ? undefined
           : typeof handlers === "function"
           ? handlers
-          : undefined; // FIXME: Method handler
+          : ((ctx) => {
+            const { method } = ctx.req;
+            if (!Array.isArray(handlers)) {
+              const maybeFn = handlers[method as Method];
+              if (maybeFn !== undefined) {
+                return maybeFn(ctx);
+              }
+            }
+            return ctx.next();
+          }) as HandlerFn<unknown, State>;
         const notFoundComponents = components.slice();
         if (mod.component !== null) {
           notFoundComponents.push(mod.component);

src/plugins/fs_routes/mod_test.tsx

@@ -646,6 +646,28 @@ Deno.test("fsRoutes - _404", async () => {
   expect(content).toContain("Custom 404 - Not Found");
 });
 
+Deno.test("fsRoutes - _404 method handler", async () => {
+  const server = await createServer({
+    "routes/_404.tsx": {
+      handlers: {
+        GET() {
+          return new Response("ok");
+        },
+      },
+    },
+    "routes/index.tsx": {
+      handlers: {
+        GET() {
+          return new Response("fail");
+        },
+      },
+    },
+  });
+
+  const res = await server.get("/invalid");
+  expect(await res.text()).toEqual("ok");
+});
+
 Deno.test("fsRoutes - _500", async () => {
   const server = await createServer({
     "routes/_500.tsx": {
@@ -665,6 +687,26 @@ Deno.test("fsRoutes - _500", async () => {
   expect(content).toContain("Custom Error Page");
 });
 
+Deno.test("fsRoutes - _500 method handler", async () => {
+  const server = await createServer({
+    "routes/_500.tsx": {
+      handlers: {
+        GET() {
+          return new Response("ok");
+        },
+      },
+    },
+    "routes/index.tsx": {
+      handlers: () => {
+        throw new Error("fail");
+      },
+    },
+  });
+
+  const res = await server.get("/");
+  expect(await res.text()).toEqual("ok");
+});
+
 Deno.test("fsRoutes - _error", async () => {
   const server = await createServer({
     "routes/_error.tsx": {
@@ -730,6 +772,26 @@ Deno.test("fsRoutes - _error nested throw", async () => {
   expect(await res.text()).toEqual("ok");
 });
 
+Deno.test("fsRoutes - _error method handler", async () => {
+  const server = await createServer({
+    "routes/_error.tsx": {
+      handlers: {
+        GET() {
+          return new Response("ok");
+        },
+      },
+    },
+    "routes/index.tsx": {
+      handlers: () => {
+        throw new Error("fail");
+      },
+    },
+  });
+
+  const res = await server.get("/");
+  expect(await res.text()).toEqual("ok");
+});
+
 Deno.test("fsRoutes - _error render component", async () => {
   const server = await createServer({
     "routes/_error.tsx": {