[ruby-core:89682] [Ruby trunk Feature#15236] add support for hash shorthand

Issue #15236 has been updated by blakewest (Blake West).


Hi all, 
I've really wanted a feature like this for a long time. I find myself often using named arguments, which I love for the clarity. But then the callers often have variables of the same name as the parameter name, making it more verbose. eg. `foo(bar: bar, baz: baz)`. If one concern here is that `{a, b, c}` looks like set syntax, then I'd be curious to get opinions on a different syntax I had thought about for a while. The general idea is to extend the `%w` idea for hashes. For example, we could do `%h{foo bar baz}` which would expand into `{foo: foo, bar: bar, baz: baz}`. In both the "%w" and "%h" cases, we're allowing for a more concise version of an often used pattern.
I think the downside is using a `%h` syntax feels "separated" from the typical hash syntax. Using a straight `{a,b,c}` is "cleaner" as there are fewer characters, and may be more intuitive to some.
But similarly, I think that actually the upside of this syntax is it's more "separated". As Matz points out, the `{a,b,c}` syntax could look like set syntax, and as shevegen points out, it could be confusing for beginners. Neither of these problems would exist using %h, as it would pretty clearly be a "special" syntax, used by people who know what it's doing. Also, using `%h{}` would enable not having to use commas, which could make it even more compact

I'll leave with a few more examples of what I'd be suggesting.

~~~ ruby
def foo(param1:, param2:)
  param + param2
end

param1 = 7
param2 = 42

foo(%h{param1 param2})

def respond_with(resource, options)
  meta = extract_meta(resource, options)
  etc = extract_etc(resource, options)

  %h{ resource meta etc }
end

# destructuring could obviously be left for later.
%h{data meta etc} = {data: [1,2,3], meta: {mobile: true}, etc: "more info"}
~~~

Thoughts?
 

----------------------------------------
Feature #15236: add support for hash shorthand
https://bugs.ruby-lang.org/issues/15236#change-74722

* Author: ignatiusreza (Ignatius Reza Lesmana)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
PR in github: https://github.com/ruby/ruby/pull/1990

inspired by javascript support for object literal shorthand notation `{ a }`, which will be expanded into `{ a: a }`..

to avoid ambiguity, this shorthand is only supported when hash is defined with `{ }` notation.. in other situation where the brackets is optional, e.g. function call, we still need to write it in full (`m(a : a)` instead of `m(a)`, or `m(a, b, c: c)` instead of `m(a, b, c)`..



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