Shopify App Errors: How to Fix "ensureInstalledOnShop did not receive a shop query argument"

Decoding the "ensureInstalledOnShop" Error in Shopify App Express

Hey everyone! Ever run into that head-scratcher of an error: [shopify-app/ERROR] ensureInstalledOnShop did not receive a shop query argument when building a Shopify app with Express? Yeah, it's a common one, and I recently saw a great discussion about it in the Shopify Community that I wanted to share some insights from. It can really halt your progress, but thankfully, it's usually a pretty straightforward fix.

The Problem: Missing Shop Query Parameter

So, the core issue is that the ensureInstalledOnShop() function from @shopify/shopify-app-express needs that shop query parameter in the URL. This parameter tells your app *which* Shopify store it's interacting with. When the route handling the frontend rendering doesn't receive this parameter, things go south pretty quickly, and you see that dreaded error message. This is exactly what happened to @snsd in the community forum. They were seeing the error pop up when trying to open their app, even though they expected Shopify to automatically pass the shop parameter.

Here's the code snippet @snsd shared:

app.use("*", _async_ (req, res, next) => {
  // Skip Shopify install check for API routes
  if (req.path.startsWith("/api")) {
    _return_ next();
  }

  // Only allow GET requests for frontend rendering
  if (req.method !== "GET") {
    _return_ next();
  }

  // Error occurs here
  _return_ shopify.ensureInstalledOnShop()(req, res, _async_ () => {
    _return_ res
      .status(200)
      .set("Content-Type", "text/html")
      .send(
        readFileSync(join(STATIC_PATH, "index.html"))
          .toString()
          .replace("%VITE_SHOPIFY_API_KEY%", process.env.SHOPIFY_API_KEY || "")
      );
  });
});

The Solution: Guarding Your Routes

The fix, as pointed out by @snsd, involves adding a guard to ensure the shop parameter exists before calling ensureInstalledOnShop(). This prevents the app from crashing when the parameter is missing. Basically, you're checking if req.query.shop has a value before proceeding.

Here's the suggested code:

app.use("*", (req, res, next) => {
  if (req.path.startsWith("/api")) return next();
  if (req.method !== "GET") return next();

  if (!req.query.shop) {
    return res.redirect("/api/auth");
  }

  return shopify.ensureInstalledOnShop()(req, res, next);
});

Step-by-Step Instructions to Implement the Fix

Okay, let's break down how to implement this solution in your own Shopify app:

1. Locate your middleware setup: Find the file where you're configuring your app's middleware. This is often in web/index.js or a similar file.
2. Add the conditional check: Insert the following code block before your shopify.ensureInstalledOnShop() call:

   if (!req.query.shop) {
     return res.redirect("/api/auth");
   }
   

3. Adjust the redirect URL: Make sure the /api/auth redirect URL points to your app's authentication route. This is where you'll handle the Shopify OAuth flow to get the shop parameter.
4. Test your app: Restart your development server (npm run dev) and try accessing your app again. The error should be gone, and you should be redirected to the authentication flow if the shop parameter is missing.

Why This Works

The ensureInstalledOnShop() function is crucial for ensuring that your app is properly installed on the Shopify store attempting to access it. It verifies the installation status and handles the OAuth flow if needed. However, it *needs* the shop parameter to know which store to check. By adding the conditional check, you're preventing the function from being called without this essential piece of information, thus avoiding the error.

Additional Tips

• Double-check your Shopify App setup: Make sure your app is correctly configured in your Shopify Partner account. Verify the app URL and ensure it matches your development server's address.
• Review your OAuth flow: Ensure your OAuth flow is correctly implemented and that it properly redirects users back to your app with the shop parameter.
• Examine your network requests: Use your browser's developer tools to inspect the network requests and confirm that the shop parameter is present in the URL when accessing your app.

So, there you have it! By adding a simple check for the shop query parameter, you can easily resolve this common error and get your Shopify app back on track. It's all about making sure that ensureInstalledOnShop() gets the information it needs to do its job. Happy coding!