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Bug: [no-unnecessary-condition] Does not account for optional chaining on potentially-void values #6261

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cobaltt7 opened this issue Dec 21, 2022 · 1 comment · Fixed by #6432
Closed
4 tasks done

Bug: [no-unnecessary-condition] Does not account for optional chaining on potentially-void values #6261

cobaltt7 opened this issue Dec 21, 2022 · 1 comment · Fixed by #6432
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accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working good first issue Good for newcomers package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin

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@cobaltt7
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Before You File a Bug Report Please Confirm You Have Done The Following...

  • I have tried restarting my IDE and the issue persists.
  • I have updated to the latest version of the packages.
  • I have searched for related issues and found none that matched my issue.
  • I have read the FAQ and my problem is not listed.

Playground Link

https://typescript-eslint.io/play/#ts=4.9.4&sourceType=module&code=DYUwLgBAbghgTgSxgI1BAvBARCgxliGAZwiLEQDsBzCAH2gHsEATAbgFgAoL2RFUAPwA6ANoAGALqsgA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0yHJgBNK+SpPRRE0aB2iRwYAL4gtQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eFYDAruuGAL4g9A

Repro Code

let variable = "abc" as string | void;

variable?.[0];

ESLint Config

module.exports = {
  parser: "@typescript-eslint/parser",
  rules: {
    "@typescript-eslint/no-unnecessary-condition": "error"
  },
};

tsconfig

{
  "compilerOptions": {
    "strict": true
  }
}

Expected Result

No problems

Actual Result

The third line reports an error - Unnecessary optional chain on a non-nullish value.

Additional Info

Related to #5766. That PR did not extend to the optional chaining part of this rule.
This is caused by

typescript-eslint/packages/type-utils/src/predicates.ts

Line 28 in ccd45d4

return (flags & (ts.TypeFlags.Null | ts.TypeFlags.Undefined)) !== 0;
not checking for void, only null and undefined.
@cobaltt7 cobaltt7 added bug Something isn't working package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin triage Waiting for team members to take a look labels Dec 21, 2022
@JoshuaKGoldberg
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👍 same as #5254 (comment). This is a bug in the rule - though as per #5255 - you really should avoid using | void. See conversation in that issue for why we only reluctantly mark these as accepting PRs 😄

@JoshuaKGoldberg JoshuaKGoldberg added good first issue Good for newcomers accepting prs Go ahead, send a pull request that resolves this issue and removed triage Waiting for team members to take a look labels Dec 21, 2022
@cparros cparros mentioned this issue Feb 7, 2023
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accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working good first issue Good for newcomers package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin
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