Variables with boolean value false are overwritten in Request.prepare!

[mikeharty]

In the Request class, the prepare! method applies default values to variables using conditional assignment:

operation.variables.each do |v|
  @variables[v.name] ||= v.default_value
end

Unfortunately,false is falsey (obviously), so it is always overwritten with the value in v.default_value (which could be nil or true).

This is critical, I'd think, considering it can flip false boolean values to true if the default is true.

Script to reproduce (run from project root):

require_relative 'lib/graphql/stitching'
require_relative 'lib/graphql/stitching/request'

query = <<~GRAPHQL
  query($a: Boolean, $b: Boolean, $c: Boolean = true) {
    base(a: $a, b: $b, c: $c) { id }
  }
GRAPHQL

variables = { "a" => true, "b" => false, "c" => false }
request = GraphQL::Stitching::Request.new(GraphQL.parse(query), variables: variables)
request.prepare!

puts request.variables
# {"a"=>true, "b"=>nil, "c"=>true}

Fix is simple, I'll open a PR in a moment with the fix + a test.

[gmac]

Good catch!

[gmac]

Resolved by #92