Provide error when using non-theme access app password

Author: aswamy

.changeset/gorgeous-students-work.md

@@ -0,0 +1,5 @@
+---
+'@shopify/theme': patch
+---
+
+Provide error when using non-theme access app password

packages/theme/src/cli/flags.ts

@@ -1,5 +1,6 @@
 import {Flags} from '@oclif/core'
 import {normalizeStoreFqdn} from '@shopify/cli-kit/node/context/fqdn'
+import {AbortError} from '@shopify/cli-kit/node/error'
 import {resolvePath, cwd} from '@shopify/cli-kit/node/path'
 
 /**
@@ -17,6 +18,13 @@ export const themeFlags = {
   password: Flags.string({
     description: 'Password generated from the Theme Access app.',
     env: 'SHOPIFY_CLI_THEME_TOKEN',
+    parse: async (input) => {
+      if (input.startsWith('shptka_')) {
+        return input
+      }
+
+      throw new AbortError('Invalid password. Please generate a new password from the Theme Access app.')
+    },
   }),
   store: Flags.string({
     char: 's',