tsdjs/tsd

expectError strict behaviour

Open

#40 opened on Sep 30, 2019

View on GitHub
 (4 comments) (0 reactions) (0 assignees)TypeScript (68 forks)user submission
help wantedquestion

Repository metrics

Stars
 (2,551 stars)
PR merge metrics
 (No merged PRs in 30d)

Description

I need feedback on the behaviour of the expectError assertion.

The expectType assertion is strict. Which means that expectType<string | number>(concat('a', 'b')) will fail because string | number is defined too wide. See the docs.

I didn't change anything for expectError as I wasn't sure on the exact behaviour.

@cartant asked if it would behave like this (see https://github.com/ReactiveX/rxjs/issues/4871#issuecomment-535725717).

expectError<string | number>(add(1, 2));
//=> no error

The reason behind it could be that because the type is too wide, the assertion is an error and that's what you expect.

I also discussed this with @sindresorhus and he indicated that maybe we should hard fail on that assertion.

I definitely could use feedback on this topic here :).

// @BendingBender

Contributor guide

Research direction
Investigate the current implementation of expectError in tsd and discuss whether strict behavior (like expectType) should be applied, potentially causing hard failures on wide types.
Tech stack
typescript
Domain
testingdeveloper experience
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
TypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60