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Array.FindIndex has incorrect ArgumentOutOfRangeException description for 'startIndex' parameter. #9719

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Fast-Nick opened this issue Mar 14, 2024 · 2 comments · May be fixed by #9720
Open

Array.FindIndex has incorrect ArgumentOutOfRangeException description for 'startIndex' parameter. #9719

Fast-Nick opened this issue Mar 14, 2024 · 2 comments · May be fixed by #9720
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area-System.Runtime Pri3 Indicates issues/PRs that are low priority untriaged New issue has not been triaged by the area owner

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@Fast-Nick
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Fast-Nick commented Mar 14, 2024 •
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Example of what it looks like today (see bottom line of documentation):

        //     .........
        // Exceptions:
        //   T:System.ArgumentNullException:
        //     array is null. -or- match is null.
        //
        //   T:System.ArgumentOutOfRangeException:
        //     startIndex is outside the range of valid indexes for array.
        public static int FindIndex<T>(T[] array, int startIndex, Predicate<T> match);

It effectively says that the method accepts [0 <= startIndex < Length] with Length exclusive.
But what the method actually accepts is [0 <= startIndex <= Length] with Length inclusive.

The real behavior of the startIndex is identical to String.Substring, which has the following description instead:

        //   T:System.ArgumentOutOfRangeException:
        //     startIndex is less than zero or greater than the length of this instance.

To be correct and easy to understand the FindIndex documentation should thus say:

        //     startIndex is less than zero or greater than the length of the array.
@issues-automation issues-automation bot added the Pri3 Indicates issues/PRs that are low priority label Mar 14, 2024
@dotnet-policy-service dotnet-policy-service bot added the untriaged New issue has not been triaged by the area owner label Mar 14, 2024
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Tagging subscribers to this area: @dotnet/area-system-runtime

Fast-Nick added a commit to Fast-Nick/dotnet-api-docs that referenced this issue Mar 14, 2024
@Fast-Nick
Update Array.xml change ArgumentOutOfRangeException description for '…
d6c5f37 
…startIndex' parameter on FindIndex methods

Changed it to match String.Substring, because the behavior is identical (and original description is arguably wrong or hard to understand).

Fixes: dotnet#9719
@Fast-Nick Fast-Nick linked a pull request Mar 14, 2024 that will close this issue
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@Fast-Nick
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Adding a draft for now - it does fix the exact issue described, but the phrase "... is outside the range of valid indexes for ..." exists on a lot of other Array methods too, so it's probably ideal to go through all of them and make sure the phrasing is consistent for all methods which have this bound-check behavior.

...but I don't have time to do that today so will look at it / go through all methods later.

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