[ruby-core:108713] [Ruby master Bug#18771] IO.foreach/.readlines ignores the 4th positional argument

Issue #18771 has been updated by jeremyevans0 (Jeremy Evans).


I've submitted a pull request to fix this: https://github.com/ruby/ruby/pull/5953

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Bug #18771: IO.foreach/.readlines ignores the 4th positional argument
https://bugs.ruby-lang.org/issues/18771#change-97764

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* Priority: Normal
* ruby -v: 3.0.3
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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The `IO.readlines` method has the following signature:

```
readlines(name, sep, limit [, getline_args, open_args]) → array
```

The last arguments `getline_args`, `open_args` are accepted as keyword arguments, so there are actually 3 positional arguments - `name`, `sep`, and `limit`.

But if the method is called with any 4th positional argument - then it's just ignored. But I would expect an exception to be raised e.g. "ArgumentError: wrong number of arguments (given 4, expected 1..3)"

```ruby
File.readlines('file.txt', "\n", 10)
=> ["abc\n", "\n", "def\n"]
File.readlines('file.txt', "\n", 10, {})
=> ["abc\n", "\n", "def\n"]
File.readlines('file.txt', "\n", 10, {chomp: true})
=> ["abc\n", "\n", "def\n"]
File.readlines('file.txt', "\n", 10, false)
=> ["abc\n", "\n", "def\n"]
File.readlines('file.txt', "\n", 10, nil)
=> ["abc\n", "\n", "def\n"]
```

It's relevant to the `IO.foreach` method as well.

Expected behavior - an ArgumentError exception to be raised.



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