Feature #17292


Hash Shorthand / Punning

Added by baweaver (Brandon Weaver) 12 months ago. Updated about 1 month ago.

Target version:


Set Literal vs Javascript Object Punning

There was a proposal for a Set literal here:

set = { 1, 2, 3 }

...but it was brought up that this is similar to the Javascript Object punning, or Object shorthand syntax:

const a = 1, b = 2, c = 3;

const punnedObject = { a, b, c }
// => { a: 1, b: 2, c: 3 }

Proposition: I believe we should use brackets ({}) for a shorthand Hash syntax similar to Javascript.

Hash Punning

My first proposal in this feature request is Hash punning, or Hash shorthand:

a = 1
b = 2
c = 3

{ a:, b:, c: }
# => { a: 1, b: 2, c: 3 }

This syntax avoids the ambiguous syntax of empty block ({}) versus empty set ({}), and with the presence of Symbols it introduces a distinct syntax that would be easier to parse against.

One potential issue would be mixed syntax:

{ a:, b: 2 }
# => { a: 1, b: 2 }

Method Punning

This syntax can also be used for keyword argument and method call punning:

def method_name(a:, b:, c:)
  a + b + c

a = 1
b = 2
c = 3

method_name(a:, b:, c:)
# => 6

I believe this existing syntax for required keywords gives credence to the idea of introducing punning to Ruby, as it's very similar to existing syntax, and therefor feels "Ruby-like".

Pattern Matching

This syntax is also already present and used in pattern matching, making it already part of the language:

case { x: 1, y: 2 }
in { x:, y: }
  { x:, y: y + 1} # new
  # ...

I believe this further justifies the case for punning syntax.

Related issues

Related to Ruby master - Feature #18124: Hash shorthands (matching constructors functionality in JS)ClosedActions
Is duplicate of Ruby master - Feature #14579: Hash value omissionClosedmatz (Yukihiro Matsumoto)Actions
Actions #1

Updated by mame (Yusuke Endoh) 12 months ago

Updated by baweaver (Brandon Weaver) 12 months ago

I would agree this is a duplicate, but in the last year we have had the introduction of the pattern matching syntax which makes this less of a syntactical oddity than it may have been in the past.

Actions #3

Updated by mame (Yusuke Endoh) 2 months ago

  • Related to Feature #18124: Hash shorthands (matching constructors functionality in JS) added
Actions #4

Updated by shugo (Shugo Maeda) about 1 month ago

  • Status changed from Open to Closed

Thank you.
Committed in c60dbcd1c55cd77a24c41d5e1a9555622be8b2b8.


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