Has anybody ever seen this ClojureScript error?

Unable to construct gen at: [:context] for: object?
Error: Unable to construct gen at: [:context] for: object?
    at Object.cljs$spec$alpha$gensub [as gensub] (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/spec/alpha.cljs:278:14)
    at Object.cljs$spec$alpha$re_gen [as re_gen] (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/spec/alpha.cljs:1187:32)
    at /home/arichiardi/git/laputa/lambda-cqrs/out/cljs/spec/alpha.cljs:1174:34
    at /home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.cljs:4691:16
    at cljs.core.map.cljs$core$IFn$_invoke$arity$4 (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.js:17634:3)
    at cljs.core.LazySeq.sval (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.cljs:3394:18)
    at cljs.core.LazySeq.cljs$core$ISeqable$_seq$arity$1 (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.cljs:3384:1)
    at Object.cljs$core$seq [as seq] (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.cljs:1210:25)
    at Object.cljs$core$every_QMARK_ [as every_QMARK_] (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/core.cljs:4183:10)
    at Object.cljs$spec$alpha$re_gen [as re_gen] (/home/arichiardi/git/laputa/lambda-cqrs/out/cljs/spec/alpha.cljs:1191:30)

It seems to be coming from this fspec

(s/def :http/callback
  (s/fspec :args (s/cat :context object?
                        :error #(instance? js/Error %)
                        :response object?)))

I guess I cannot fspec a higher order function that accepts a JS object yet?

@richiardiandrea Right—`object?` is not present here https://github.com/clojure/clojurescript/blob/master/src/main/cljs/cljs/spec/gen/alpha.cljs#L87-L141

Thanks for the new CLJS release.

Question about extern inference improving. How much should we trust it and what should we watch out for?

@olivergeorge hrm I guess report stuff that doesn’t work?

Advanced compilation etc.

Fair enough. Thanks David. Is there anywhere that describes how things improved?

how do you deal with the browser back button in a SPA?

https://developer.mozilla.org/en-US/docs/Web/API/History_API

goog.history has helpers

https://google.github.io/closure-library/api/goog.history.Html5History.html

@olivergeorge hrm not outside of tickets and commit history

I am trying to adapt David Nolen's recent article about using webpack with cljs to include the prosemirror package in a small project, but I am having some challenges getting the mapping right. I have provided a gist here https://gist.github.com/maacl/3af5c646e5139b4fc9eacc46f2eb1218 with the relevant files. The output I get is "undefined". It appears from my testing that prosemirror-state is mapped directly to the EditorState object, whereas I would like for prosemirror-state just to be mapped to the prosemirror-state ns and access EditorState using prosemirror-state/EditorState.

whatever you want you need to make it so in your index.js file

JavaScript doesn’t have namespaces so there’s no way to magically make this work

@mac ^

window.PromiseMirrorState = {EditorState: EditorState}; etc.

@dnolen Sorry for the confusion, I did not mean to imply that js has nss. If I do above how would then access EditorState from core.cljs?

promise-mirror-state/EditorState

@dnolen Ah, ok.

you can determine the structure of the library yourself in index.js is all I was trying to say

I get Uncaught TypeError: Cannot read property 'EditorState' of undefined - but I can access EditorState from the console via ProseMirrorState.EditorState

@dnolen ^

I think this is a red-herring - you have other problems

:global-exports {foo [X Y]} is meaningless

and will probably generate broken code

it must be {provide-name JavaScriptGlobalName}

I’ve created an issue to validate :global-exports to avoid this kind of misunderstanding https://dev.clojure.org/jira/browse/CLJS-2781

@mac another thing I recommend is trying to get one import / export to work for now - remove all the other stuff

if you can’t get that to work then I’ll look at it - it’s minimal enough to show me if there’s an issue

@dnolen Ok, reducing to one import and testing again.

@dnolen Ok I updated the gist to reflect the current code, that still produces the same result.

@mac your gist is lacking in sufficient information to reproduce 🙂

what packages do I need to install?

yarn add prosemirror is what I did

but yarn webpack fails for me

@dnolen Sorry did not consider that. You need to do yarn add prosemirror-state

@dnolen Other than that the steps are identical to your article.

@mac it works for me

I see EditorState logged in the JS console

@dnolen I get a warning re using production mode when doing yarn webpack. Can that be the culprit?

Nope expected

I really don’t see how this can’t work

@dnolen This is very strange. I thought I might be missing a "-" somewhere or something silly like that. My current error is "Uncaught TypeError: Cannot read property 'EditorState' of undefined at core.cljs:4"

yeah I really don’t know, I can’t reproduce your problem

there’s literally nothing different from what you are doing and what the guide covers

and I can’t make it fail the way you are describing

@mac I’m assuming you deleted out and tried a fresh build just in case?

@dnolen I did not, but I did now and that fixed the problem. Sorry, I had no I idea that deleting out was necessary.

it’s not necessary

but back when you had the bad :global-exports maybe that messed stuff up

definitely would trigger bad code gen

@dnolen Ah, got it. And I see now, how to achieve what I wanted using index.js. Thanks a lot.

np

It sounds like a common cause for problems is just forgetting to clear out old bad state when getting this stuff working.

well in this case we need to validate since :global-exports leads to code gen and bad input will produce bad output

and re-running compile won’t fix it because nothing in your own sources changed

Yeah. Just almost think a FAQ could suggest cleaning old build artifacts as a troubleshooting step. Hah. Then again that may be just a common step for many build related things.

How to require libs like material-ui on clojurescript? I added "@material-ui/core" "1.2.1" in my :npm-deps But I dont know how to require. (on js doc is: import Button from '@material-ui/core/Button'; ) When I try ["@material-ui/core/Button" :as button] I get Error: Undefined nameToPath for _CIRCA_material_ui.core.Button on browser (but no error/warning on build)

scoped modules don’t work with :npm-deps due to a bug in Google Closure

I have a PR outstanding for that

It's a closure regression? On older versions of cljs/closure compiler may work?

it doesn’t have that particular bug but no idea if it will work

when you are setting a project up it is often helpful to just include a clean step while you are iterating your configuration i.e. rm -rf out; clj -m cljs.main -c example.core

is it possible to rebind value of a var (e.g. clojure.core/deref), but only for the immediate syntactic scope? e.g. I want to capture deref inside of a function body, but not within any functions called inside of the body

@lilactown Maybe you could let a local to shadow clojure.core/deref

(let [deref (fn [_] ,,,)] (deref 1) ,,,)

hmm I tried that and i thought it didn’t work. I’ll try again

the problem is that I’d like to be able to use @ which expands to clojure.core/deref… fully qualified

so it’s not using my local shadow

Right, I think you'd have to explicitly use deref.

newts 😞