8000 Bug: [no-unnecessary-condition] False positive on dynamic access of generic value · Issue #10600 · typescript-eslint/typescript-eslint · GitHub
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Bug: [no-unnecessary-condition] False positive on dynamic access of generic value #10600

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justinsmid opened this issue Jan 3, 2025 · 1 comment · Fixed by #10602
Closed
4 tasks done

Bug: [no-unnecessary-condition] False positive on dynamic access of generic value #10600

justinsmid opened this issue Jan 3, 2025 · 1 comment · Fixed by #10602
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accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin

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@justinsmid
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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=5.7.2&fileType=.tsx&code=KYDwDg9gTgLgBASwHY2FAZgQwMbDgMQQBtUoAZBAZxgElUBbSmpMAVxgB4AVAPjgG8AUHEQNKALjgBBKFEwBPbj2FxKwTFGwALSdSjIA5oIC%2BgwaEiw46VkmwwEEJNeKkK1OsEYAheQGlgeUolAAoVflEvSgAaVXVNLThjSUISNHdaMWY2Tl5olQBrQIlpWQUOIvkIdDg8wQBKSRk5RV4BFWwnajgiCAB3NABhTDUAZXjtOABeOI1tADoYCDJ%2BoZHgEPqzEShgGFYoZwQxefRXNBCQ46966eUREUrKecoIeg2Qytupvmv6AG1KgBdAD8iwgoxg%2BiQBk24JWAygwzUcOQ2CIrAAJsBKCFeojkcBxnMtPV6vkRFtjEA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0yHJgBNK%2BSpPRRE0aB2iRwYAL4gtQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA&tokens=false

Repro Code

export interface FilterListItemsInput<T> {
  items: Array<T>
  search: string
}

export function filterListItemsByKeys<T>(
  { items, search }: FilterListItemsInput<T>,
  keys: Array<keyof T>,
): Array<T> {
  const lowerCaseSearch = search.toLowerCase()

  return items.filter((item) =>
    keys.some((key) => item[key]?.toString().toLowerCase().includes(lowerCaseSearch)),
  )
}

ESLint Config

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

tsconfig

{
  "compilerOptions": {
    "strictNullChecks": true
  }
}

Expected Result

I expect the code above not to error because item[key] can be nullish, but the ESLint rule says it can't.

Actual Result

ESLint: Unnecessary optional chain on a non-nullish value.(@typescript-eslint/ no-unnecessary-condition)

Additional Info

I found #9754 which seems similar, though I don't think it's quite the same.
@justinsmid justinsmid 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 Jan 3, 2025
@bradzacher
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Your repro can be vastly simplified down to:

function foo<T>(arg: T, key: keyof T) {
  if (arg[key]?.toString()) {
    return true;
  }
}

This looks like false positive for the optional chaining codepath considering that we don't error on this:

function foo<T>(arg: T, key: keyof T) {
  if (arg[key]) {
    return true;
  }
}

@bradzacher bradzacher added accepting prs Go ahead, send a pull request that resolves this issue and removed triage Waiting for team members to take a look labels Jan 3, 2025
@ronami ronami mentioned this issue Jan 3, 2025
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@github-actions github-actions bot added the locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. label Jan 21, 2025
@github-actions github-actions bot locked as resolved and limited conversation to collaborators Jan 21, 2025
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accepting prs Go ahead, send a pull request that resolves this issue bug Something isn't working locked due to age Please open a new issue if you'd like to say more. See https://typescript-eslint.io/contributing. package: eslint-plugin Issues related to @typescript-eslint/eslint-plugin
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