strings,bytes: improve doc of Split* functions for the empty string case #19726
Description
In go 1.8 the behaviour of strings.Split{,N,After,AfterN} functions is not explicitly documented for the special case of splitting the empty string "". The functions return a slice with a single element which is the empty string.
The problem is that the Go behaviour is not the same as in other programming languages with functions with a similar name where for the same input the result is a zero-length array.
In Go (playground):
fmt.Printf("%q\n", strings.SplitAfter("a", ":"))
fmt.Printf("%q\n", strings.SplitAfter("", ":"))
// Output:
// ["a"]
// [""]
In Perl 5 the result is a zero-length list:
perl -mData::Dumper=Dumper -E 'say Dumper([ split /:/, $_ ]) for "a", ""'
$VAR1 = [
'a'
];
$VAR1 = [];
This leads to wrong expectations from users of the functions (especially when porting code from other languages) and may lead to security issues such as incorrect input validation or deny of service.
The documentation should be improved by documenting specially this corner case.