combineLatest only throws cryptic error at subscription runtime instead of clear type error
Patrick-DS-Smartly opened this issue · 0 comments
Describe the bug
I noticed this bug by using combineLatest
in the following way (you can run this in a REPL for example)
const { combineLatest, of } = require('rxjs')
combineLatest([of(0), undefined]).subscribe()
which gives the corresponding stacktrace:
TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, ReadableStream, Array, AsyncIterable, or Iterable.
at Object.createInvalidObservableTypeError (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/util/throwUnobservableError.js:5:12)
at Object.innerFrom (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/innerFrom.js:93:36)
at Object.from (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/from.js:7:78)
at <path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/combineLatest.js:42:41
at maybeSchedule (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/combineLatest.js:72:9)
at _loop_1 (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/combineLatest.js:41:17)
at <path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/combineLatest.js:61:17
at maybeSchedule (<path-to-my-project>/node_modules/rxjs/dist/cjs/internal/observable/combineLatest.js:72:9)
I'm ok with the error itself, but I'm not ok with the fact that the stacktrace sits entirely within the RxJS library. The issue becomes problematic in a codebase which is very large and uses RxJS extensively because it gives literally nowhere to start when the time comes to figure out which call of combineLatest
caused the issue. In fact, from that stacktrace, it's not even clear that it's a call to combineLatest
that caused the issue, since the only indication I have here is that combineLatest.js
appears somewhere in the stacktrace.
Expected behavior
I would expect the following code
const { combineLatest, of } = require('rxjs')
combineLatest([of(0), undefined])
(without subscription) to throw the following:
TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, ReadableStream, Array, AsyncIterable, or Iterable.
at <location in my code, not in the RxJS library>
at <rest of the stacktrace>.
Reproduction code
const { combineLatest, of } = require('rxjs')
combineLatest([of(0), undefined])
Reproduction URL
https://stackblitz.com/edit/rxjs-gdmq8d?file=index.ts
Version
7.8.0
Environment
No response
Additional context
No response