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Rule request: Use min() or max() instead of sorted().first or sorted().last #1932

tomquist opened this Issue Nov 6, 2017 · 1 comment


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tomquist commented Nov 6, 2017

New Issue Checklist

Rule Request

If this is a new rule request, please ignore all sections below this one, format
this issue's title as Rule Request: [Rule Name] and describe:

  1. Why should this rule be added? Share links to existing discussion about what
    the community thinks about this.
    First sorting a sequence and then just reading the first or last element is unnecessarily consuming memory and is much slower (O(n log(n))) than searching for the minimum element in a sequence (O(n)).

  2. Provide several examples of what would and wouldn't trigger violations.

    // Should trigger
    myList.sorted(by: { $0.description < $1.description }).first
    myList.sorted(by: >).first { $0 + 1 }.sorted().first
    myList.sorted(by: someFunction).first { $0 + 1 }.sorted { $0.description < $1.description }.first
    myList.sorted(by: { $0.description < $1.description }).last { $0 + 1 }.sorted().last
    myList.sorted(by: someFunction).last { $0 + 1 }.sorted { $0.description < $1.description }.last
    // Should not trigger
    let min = myList.min()\n
    let min = myList.min(by: { $0.description < $1.description })
    let min = myList.min(by: >)
    let min = myList.max()
    let min = myList.max(by: { $0 < $1 })
  1. Should the rule be configurable, if so what parameters should be configurable?
    Just severity.
  2. Should the rule be opt-in or enabled by default? Why?
    The rule may lead to false positives on non-sequence API where there is no min/max function. Similar to first_where and contains_over_first_not_nil this rule should be opt-in.

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jpsim Nov 8, 2017


Done in #1933.


jpsim commented Nov 8, 2017

Done in #1933.

@jpsim jpsim closed this Nov 8, 2017

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