Add Node#loc? to determine if a node has a given location

[dvandersluis]

Following #345, it'd be helpful to have a helper method for loc.respond_to?(:foo) && loc.foo, which happens in a number of places in rubocop. I've added Node#loc?(:foo) to accomplish this, and redefined loc_is? to use loc?.

There were a couple places in rubocop-ast that just used loc.respond_to? without the and. I updated the one for ternary? because it should always be present in a ternary. I did not update MethodDispatchNode#selector because there's a lot of node types that include that and selector is not well tested for that (and I'm not sure if it's possible to have a keyword location in these cases without a value).

[marcandre]

TBH, I wonder why we never thought of simply adding the missing locations. The "difference" between not responding to a loc and having that loc as nil is meaningless and just an annoyance. Seems to me that the location for a node of type s should always respond to the same locations no matter what.

[dvandersluis]

So the problem is that the parser gem defines quite a number of different Parser::Source::* location classes, and they are used for specific situations.

For example, an if node uses Parser::Source::Map::Condition and looks like this:

#<Parser::Source::Map::Condition:0x000000013877fba8
 @begin=nil,
 @else=#<Parser::Source::Range /src/rubocop/test.rb 44...48>,
 @end=#<Parser::Source::Range /src/rubocop/test.rb 55...58>,
 @expression=#<Parser::Source::Range /src/rubocop/test.rb 31...58>,
 @keyword=#<Parser::Source::Range /src/rubocop/test.rb 31...33>,
 @node=s(:if,
  s(:send, nil, :foo),
  s(:send, nil, :bar),
  s(:send, nil, :baz))>

but its ternary form uses Parser::Source::Map::Ternary and looks like this:

#<Parser::Source::Map::Ternary:0x000000012295e228
 @colon=#<Parser::Source::Range /src/rubocop/test.rb 41...42>,
 @expression=#<Parser::Source::Range /src/rubocop/test.rb 31...46>,
 @node=s(:if,
  s(:send, nil, :foo),
  s(:send, nil, :bar),
  s(:send, nil, :baz)),
 @question=#<Parser::Source::Range /src/rubocop/test.rb 35...36>>

As well, there are a lot of places where we act without knowing exactly what node type is being evaluated, which is another reason why the locations can differ.

So it's probably not straightforward to have a consistent interface across the board.

[dvandersluis]

@marcandre when you have time can you take another look please? 🙌

[marcandre]

Cool, thanks

[dvandersluis]

Thanks @marcandre!

[marcandre]

Thank you @dvandersluis ❤️

Released as 1.38.0