From 70534dacebc69e05d2674a08b4b75b352b8a8913 Mon Sep 17 00:00:00 2001
From: Joe Mou <dev@mou.fo>
Date: Tue, 27 Jan 2026 11:23:11 -0500
Subject: Propagate GitHub HTTP errors

Render `error.eta` on HTTP error from GitHub.

Implemented with Gemini.
---
 src/index.ts        | 31 +++++++++++++++++++++++--------
 src/scraper.test.ts | 12 +++++++++++-
 src/scraper.ts      | 11 +++++++++++
 3 files changed, 45 insertions(+), 9 deletions(-)

(limited to 'src')

diff --git a/src/index.ts b/src/index.ts
index 388b1e0..51e8cf2 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,10 +1,11 @@
 import { createAdaptorServer, serve } from "@hono/node-server";
 import { serveStatic } from "@hono/node-server/serve-static";
 import { Eta } from "eta";
-import { Hono } from "hono";
+import { type Context, Hono } from "hono";
+import type { StatusCode } from "hono/utils/http-status";
 import path from "node:path";
 import url from "node:url";
-import { getGitHubBlob, getGitHubRepo, getGitHubTree } from "./scraper.ts";
+import { getGitHubBlob, getGitHubRepo, getGitHubTree, GitHubHTTPError } from "./scraper.ts";
 
 const __dirname = path.dirname(url.fileURLToPath(import.meta.url));
 
@@ -17,22 +18,36 @@ app.get("/", async (c) => {
   return c.html(await eta.renderAsync("home.eta", {}));
 });
 
+async function tryRender<T extends object>(c: Context, template: string, promise: Promise<T>) {
+  let data: T;
+  try {
+    data = await promise;
+  } catch (e) {
+    if (e instanceof GitHubHTTPError) {
+      c.status(e.status as StatusCode);
+      const message = `GitHub responded with HTTP ${e.status} ${e.message}`;
+      return c.html(await eta.renderAsync("error.eta", { title: e.message, message }));
+    } else {
+      c.status(500);
+      return c.html(await eta.renderAsync("error.eta", { message: "" + e }));
+    }
+  }
+  return c.html(await eta.renderAsync(template, data));
+}
+
 app.get("/:owner/:repo", async (c) => {
   const { owner, repo } = c.req.param();
-  const data = await getGitHubRepo(owner, repo);
-  return c.html(await eta.renderAsync("repo.eta", data));
+  return tryRender(c, "repo.eta", getGitHubRepo(owner, repo));
 });
 
 app.get("/:owner/:repo/tree/:branch/:path{.*}?", async (c) => {
   const { owner, repo, branch, path = "" } = c.req.param();
-  const data = await getGitHubTree(owner, repo, branch, path);
-  return c.html(await eta.renderAsync("tree.eta", data));
+  return tryRender(c, "tree.eta", getGitHubTree(owner, repo, branch, path));
 });
 
 app.get("/:owner/:repo/blob/:branch/:path{.*}", async (c) => {
   const { owner, repo, branch, path } = c.req.param();
-  const data = await getGitHubBlob(owner, repo, branch, path);
-  return c.html(await eta.renderAsync("blob.eta", data));
+  return tryRender(c, "blob.eta", getGitHubBlob(owner, repo, branch, path));
 });
 
 app.get("/:owner/:repo/raw/:branch/:path{.*}", async (c) => {
diff --git a/src/scraper.test.ts b/src/scraper.test.ts
index 3784190..adf70ae 100644
--- a/src/scraper.test.ts
+++ b/src/scraper.test.ts
@@ -1,6 +1,6 @@
 import assert from "node:assert";
 import { describe, it } from "node:test";
-import { getGitHubBlob, getGitHubRepo, getGitHubTree } from "./scraper.ts";
+import { getGitHubBlob, getGitHubRepo, getGitHubTree, GitHubHTTPError } from "./scraper.ts";
 
 describe("GitHub scraper", () => {
   describe("actions/deploy-pages repository", () => {
@@ -67,4 +67,14 @@ describe("GitHub scraper", () => {
       assert.match(data.content, /^MIT License\n\n/);
     });
   });
+
+  describe("error handling", () => {
+    it("should throw for non-existent repository", async () => {
+      await assert.rejects(getGitHubRepo("nosuchowner", "nosuchrepo"), (err) => {
+        assert(err instanceof GitHubHTTPError, "error should be an HTTPError");
+        assert.strictEqual(err.status, 404);
+        return true;
+      });
+    });
+  });
 });
diff --git a/src/scraper.ts b/src/scraper.ts
index 4feda73..b76f8c8 100644
--- a/src/scraper.ts
+++ b/src/scraper.ts
@@ -1,3 +1,13 @@
+export class GitHubHTTPError extends Error {
+  status: number;
+
+  constructor(status: number, message: string) {
+    super(message);
+    this.name = "GitHubHTTPError";
+    this.status = status;
+  }
+}
+
 interface TreeItem {
   contentType: "directory" | "file";
   name: string;
@@ -78,6 +88,7 @@ async function fetchGitHubPage(path: string): Promise<string> {
     "Accept-Language": "en-US,en;q=0.5",
   };
   const response = await fetch(`https://github.com/${path}`, { headers });
+  if (!response.ok) throw new GitHubHTTPError(response.status, response.statusText);
   return response.text();
 }
 
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