fix(server): error early on incompatible config (apiHost and apiUrl) (#…

…9808)

I was working on Redwood's server config with @Josh-Walker-GM. One of
the more unfortunate footguns is when you're serving the web side alone
while the api side is somewhere else, on a completely different host. If
you don't pass `apiHost`, and `apiUrl` isn't fully qualified, what
happens is that the web side requests itself, resulting in network
responses like this:

<img width="1532" alt="image"
src="https://github.com/redwoodjs/redwood/assets/32992335/21c6f3ec-5614-4336-9967-1ab4c25ea7db">

An easy fix that would go a long way is just erroring out if we detect
the config is incompatible and not starting the server at all:

```
# In redwood.toml, apiUrl is `/.redwood/functions`, a relative URL, and apiHost isn't passed the at the CLI:
% yarn rw serve web        
Error: If you don't provide apiHost, apiUrl needs to be a fully-qualified URL. But apiUrl is /.redwood/functions.
```

We used a specific exit code because `yarn rw serve web` is a bin that's
calling a bin `yarn rw-server-web`. We plan to fix that by deduping code
across packages, so this specific exit code is just a stopgap till we
get that work done. The reason we're doing this fix first is that again,
it's easy and would solve a big problem.

We referenced this doc on exit code conventions which stated that 64-113
was up for grabs: https://tldp.org/LDP/abs/html/exitcodes.html.

packages/cli/src/commands/serveWebHandler.js

@@ -2,6 +2,8 @@ import execa from 'execa'
 
 import { getPaths } from '@redwoodjs/project-config'
 
+import { exitWithError } from '../lib/exit'
+
 export const webSsrServerHandler = async () => {
   await execa('yarn', ['rw-serve-fe'], {
     cwd: getPaths().web.base,
@@ -11,21 +13,34 @@ export const webSsrServerHandler = async () => {
 }
 
 export const webServerHandler = async (argv) => {
-  await execa(
-    'yarn',
-    [
-      'rw-web-server',
-      '--port',
-      argv.port,
-      '--socket',
-      argv.socket,
-      '--api-host',
-      argv.apiHost,
-    ],
-    {
-      cwd: getPaths().base,
-      stdio: 'inherit',
-      shell: true,
+  try {
+    await execa(
+      'yarn',
+      [
+        'rw-web-server',
+        '--port',
+        argv.port,
+        '--socket',
+        argv.socket,
+        '--api-host',
+        argv.apiHost,
+      ],
+      {
+        cwd: getPaths().base,
+        stdio: 'inherit',
+        shell: true,
+      }
+    )
+  } catch (e) {
+    // `@redwoodjs/web-server` uses a custom error exit code to tell this handler that an error has already been handled.
+    // While any other exit code than `0` is considered an error, there seems to be some conventions around some of them
+    // like `127`, etc. We chose 64 because it's in the range where there deliberately aren't any previous conventions.
+    // See https://tldp.org/LDP/abs/html/exitcodes.html.
+    if (e.exitCode === 64) {
+      process.exitCode = 1
+      return
     }
-  )
+
+    exitWithError(e)
+  }
 }

packages/web-server/src/server.ts

@@ -18,7 +18,15 @@ interface Opts {
   apiHost?: string
 }
 
-// no help option...
+function isFullyQualifiedUrl(url: string) {
+  try {
+    // eslint-disable-next-line no-new
+    new URL(url)
+    return true
+  } catch (e) {
+    return false
+  }
+}
 
 async function serve() {
   // Parse server file args
@@ -39,6 +47,24 @@ async function serve() {
   const port = options.port ? parseInt(options.port) : redwoodConfig.web.port
   const apiUrl = redwoodConfig.web.apiUrl
 
+  if (!options.apiHost && !isFullyQualifiedUrl(apiUrl)) {
+    console.error(
+      `${chalk.red('Error')}: If you don't provide ${chalk.magenta(
+        'apiHost'
+      )}, ${chalk.magenta(
+        'apiUrl'
+      )} needs to be a fully-qualified URL. But ${chalk.magenta(
+        'apiUrl'
+      )} is ${chalk.yellow(apiUrl)}.`
+    )
+    // We're using a custom error exit code here to tell `@redwoodjs/cli` that this error has been handled.
+    // While any other exit code than `0` is considered an error, there seems to be some conventions around some of them
+    // like `127`, etc. We chose 64 because it's in the range where there deliberately aren't any previous conventions.
+    // See https://tldp.org/LDP/abs/html/exitcodes.html.
+    process.exitCode = 64
+    return
+  }
+
   const tsServer = Date.now()
 
   // Load .env files