[GROOVY-7433] API inconsistency between takeWhile, dropWhile and collectReplacements for CharSequences

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.5.0-alpha-1
• Component/s: groovy-jdk
• Labels: breaking
• Assignee: Paul King
• Reporter: Paul King
• Created: 24/May/15 07:22
• Updated: 02/May/17 02:03
• Resolved: 26/May/15 12:11

Description

When treating Strings as an iterable collection of characters, Groovy provides each character as a String of size 1, e.g.:

assert "hello".toList() == ['h', 'e', 'l', 'l', 'o']
assert "hello".toList()[0].class.name == 'java.lang.String'
"hello".each {
  assert it instanceof String
}

There are just 3 methods where this isn't the case:
takeWhile, dropWhile and collectReplacements.
These methods supply a Character instead, e.g.:

assert "he" == "hello".takeWhile {
  assert it instanceof Character
  it != 'l'
}

This issue is to fix this inconsistency. This is a breaking change but of low impact:

• Most expressions within the closure such as it != 'A' or it < 'B' will produce the same results regardless of whether a String or character is passed in.
• Expressions using methods from the String class would have needed an "as String" or ".toString()" coercion/conversion. These will still work unchanged but the coercion will no longer be required.(Which aligns them with the expressions for all other String iteration methods.)
• Closures with an explicit String arg currently don't work but would work after the change.
• Closures making use of instance methods from the Character class are breaking but those methods are "charValue()" and "compareTo(Character anotherCharacter)" and are likely rarely used (there use would be non-idiomatic Groovy).

In any case, I propose supporting the detection of supplied Closures having a char or Character argument in which case the char would be passed in as now. This would make fixing the break trivial for those cases.

Issue Links

• depends upon: GROOVY-7434 Groovy should support resolving ambiguous signatures when using ClosureParams
• relates to: GROOVY-7432 Enhance CharSequence with appropriate Iterable extension methods