When we return a union containing a promise from a function implicitly, it's often a mistake. This commit makes it so if the return type is explicit, anyPromise in the return type (whether it's part of a union or not) will flag the function. If it is intentional, make the return type explicit.

Fixes#6329

PR Checklist

Addresses an existing open issue:fixesEnhancement: [promise-function-async] flag non-async functions returning unions with non-Promise types #6329
That issue was marked asaccepting prs
Steps inCONTRIBUTING.md were taken

Overview

This implements the heuristic that@bradzacher suggested. If the return type is explicit, it allows unions with non-Promise types, but if it is implicit, it flags those.

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typescript-eslintbot commentedJan 12, 2023

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Codecov Report

Merging#6330 (be9531d) intomain (bbfed02) willdecrease coverage by0.03%.
The diff coverage is0.00%.

Additional details and impacted files

@@            Coverage Diff             @@##             main    #6330      +/-   ##==========================================- Coverage   90.61%   90.59%   -0.03%==========================================  Files         372      372                Lines       12709    12712       +3       Branches     3739     3743       +4     ==========================================  Hits        11516    11516- Misses        853      856       +3  Partials      340      340

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unittest	`90.59% <0.00%> (-0.03%)`	⬇️

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Impacted Files	Coverage Δ
.../eslint-plugin/src/rules/promise-function-async.ts	`98.07% <ø> (ø)`
packages/type-utils/src/containsAllTypesByName.ts	`0.00% <0.00%> (ø)`

ericbf changed the title~~[promise-function-async] Only allow unions in explicit return types~~feat(eslint-plugin): check for promises in implicit return types

Jan 12, 2023

ericbf force-pushed thepromise-function-async-allow-union-in-explicit-types-only branch from3527630 toc65b905Compare

January 12, 2023 22:19

JoshuaKGoldberg assignedbradzacher

Jan 31, 2023

bradzacher changed the title~~feat(eslint-plugin): check for promises in implicit return types~~feat(eslint-plugin): [promise-function-async] check for promises in implicit return types

Feb 10, 2023

bradzacher requested changes

Feb 10, 2023

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overall the changes look good - but we'll need to ensure we're not breaking the API

packages/type-utils/src/containsTypesByName.ts OutdatedShow resolvedHide resolved

packages/eslint-plugin/docs/rules/promise-function-async.mdShow resolvedHide resolved

packages/eslint-plugin/src/rules/promise-function-async.ts OutdatedShow resolvedHide resolved

bradzacher added enhancement

New feature or request

awaiting responseIssues waiting for a reply from the OP or another party labels

Feb 10, 2023

ericbf added2 commits

February 10, 2023 15:40

[promise-function-async] Only allow unions in explicit return types

ea34d23

When we return a union containing a promise from a functionimplicitly, it's often a mistake. This commit makes it so if thereturn type is explicit, any `Promise` in the return type (whetherit's part of a union or not) will flag the function. If it isintentional, make the return type explicit.Fixestypescript-eslint#6329

Refrain from renaming the type-util, instead add an optional fourth p…

be9531d