[GROOVY-8857] Add various 'object != null' syntactic sugar operators.

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 3.x
• Component/s: Compiler
• Assignee: Unassigned
• Reporter: Eric Holley
• Created: 26/Oct/18 14:22
• Updated: 12/Feb/20 01:09

Description

The Elvis operator is great in that is simplifies your code and makes it easier to read. The problem is that when the referenced object is a String or Number, and you want to use a default value when the object is null, unintended results can occur due to the null String and zero being false in Groovy truth. I find myself having to frequently use more syntactically complex code due this the issue.

My proposal is to introduce some new operators to Groovy to address this:

The first would be variation of the Elvis operator '??:' that would work just like  '?:' except that the test for truth would always be 'is the referenced object null'. So, for example:

def xyz = abc ??: 'default'

  would be compiled as:

def xyz = abc != null ? abc : 'default' 

The second would be a unary '?' operator that would look like:

if (?abc) {
   // Do something if abc is not equal null.
}

which would be compiled as:

if (abc != null) {
   // Do something if abc is not equal null.
}

The third would be the non-null Elvis assignment operator:

a ??= 'default'

which would compile as:

a = a != null ? a : 'default'

This class of operators could be referred to as the 'non-null' operators. I think that they would be a good addition to the new 3.x operators.