[ruby-core:110074] [Ruby master Bug#18978] Unexpected behaviour in Time.utc and Time.local when 8 arguments are passed in

["mame (Yusuke Endoh)" <noreply@ruby-lang.org>]

Issue #18978 has been updated by mame (Yusuke Endoh).


BTW, if you remove the eighth argument, you may also want to remove the following code to handle the argument.

https://github.com/ruby/ruby/blob/d89f8a046753e2f166ee252510aadf1579dbcd63/time.c#L2947-L2955

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Bug #18978: Unexpected behaviour in Time.utc and Time.local when 8 arguments are passed in
https://bugs.ruby-lang.org/issues/18978#change-99325

* Author: peterzhu2118 (Peter Zhu)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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GitHub PR: https://github.com/ruby/ruby/pull/6281

Time.utc and Time.local produce inconsistent and unexpected behaviour when 8 arguments is passed in.

For example, consider the following code:

```ruby
Time.utc(2000, 1, 1, 2, 3, 4, 100)
```

Here's the output on various Ruby implementations:

    MRI: 2000-01-01 02:03:04.0001 UTC
    TruffleRuby: 2000-01-01 02:03:04.0001 UTC
    Opal: 2000-01-01 02:03:04 UTC

If we add an additional argument:

```ruby
Time.utc(2000, 1, 1, 2, 3, 4, 100, 1)
```

The behaviour changes unexpectedly on MRI:

    MRI: 2000-01-01 02:03:04 UTC
    TruffleRuby: 2000-01-01 02:03:04.0001 UTC
    Opal: 2000-01-01 02:03:04 UTC

Notice that the subseconds are lost.

The PR changes it so that 8 arguments is not accepted into the methods (i.e. an ArgumentError is raised when 8 arguments is passed in). Alternatively, we could have similar behaviour as TruffleRuby, where the 8th argument is ignored. However, since the 8th argument is unused, I think it would be less confusing to the user and prevent mistakes if we raised an ArgumentError forbidding it.



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