Rails, Turbo, esbuild: TypeError: map.get is not a function

typeerror.md

(This applies to Rails 7.1, Turbo 8.0 with esbuild and propshaft)

If you're getting a "TypeError: map.get is not a function" when navigating between pages:

Uncaught (in promise) TypeError: map.get is not a function
    at fetch (application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:6485:20)
    at fetchWithTurboHeaders (application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:1153:10)
    at FetchRequest.perform (application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:1263:25)
fetch @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:6485
fetchWithTurboHeaders @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:1153
perform @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:1263
await in perform (async)
issueRequest @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:2587
visitStarted @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:2839
start @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:2543
startVisit @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:3260
visitProposedToLocation @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:2831
visitProposedToLocation @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:4751
proposeVisit @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:3251
visit @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:4654
followedLinkToLocation @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:4743
clickBubbled @ application-df30cd29ded7227ed5c827c81fa4fc9b51db518a.js:1919

The issue seems to be that, for some reason, Turbo/Stimulus is using a wrong fetch():

https://github.com/hotwired/stimulus/blob/bafb739401f54fed1b70869410979b5acd43f487/src/multimap/set_operations.ts#L10

I did not dig deep into the bundling process to understand what's happening, but the following change fixed it for me:

diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index fddc2f5..9b2bb31 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -6,8 +6,8 @@
   <%= csrf_meta_tags %>
   <%= csp_meta_tag %>
 
-  <%= javascript_include_tag "application", "data-turbo-track": "reload", defer: true %>
+  <%= javascript_include_tag "application", "data-turbo-track": "reload", type: "module" %>

Thanks!

Thank you!

thank you!

Thank you!!

thanks!

thank youuuuu

Thank you solve my problem too.

Indeed... Thanks for posting this
Problem solved

👍

wow - thanks for posting. I introduced this error trying to fix something else, spent HOURS on another problem that this was causing, then finally found your post while trying to fix yet another issue it caused. People like you deserve medals.

Thanks! ❤️