Blocks cannot be formatted when they're top-level nodes

[kkuchta]

If you parse a string like foo = bar { |x| x + 1 }, then traverse it down to the block node ({ |x| x + 1 }), trying to format that node throws an error. Here's a repro case:

require 'syntax_tree'

# Create a node visitor that walks the syntax tree looking for blocks.
class BlockFinder < SyntaxTree::Visitor
  attr_reader :first_block
  visit_method def visit_do_block(node)
    puts "found a brace block node!"
    @first_block ||= node
    # Don't traverse further
  end
  visit_method def visit_brace_block(node)
    puts "found a brace block node!"
    @first_block ||= node
    # Don't traverse further
  end
end

input_string = "foo = bar() { |x| x + 1}"
root = SyntaxTree.parse(input_string)

# use that visitor to find the first, outermost block
visitor = BlockFinder.new
visitor.visit(root)
block_node = visitor.first_block

formatter = SyntaxTree::Formatter.new(input_string, [], 80)

# !!! This throws an error:
# /Users/kevin/.rvm/gems/ruby-3.0.0/gems/syntax_tree-3.6.0/lib/syntax_tree/node.rb:1990:in `forced_do_end_bounds?': undefined method `call' for nil:NilClass
formatter.format(block_node)

# But if I comment that line out and then fake that this block node is nested
# within a parent node, it works:
formatter.instance_variable_set(:@stack, [proc {SyntaxTree::Program.new(statements: [], location: nil)}])
formatter.format(block_node)

formatter.flush
output_string = formatter.output.join
puts output_string # Prints  { |x| x + 1 }

The issue seems to be that forced_do_end_bounds in BlockFormatter inspects the parent node and doesn't handle when it doesn't exist.

PS: thanks for the great tool and, honestly, the very readable source!

[kddnewton]

Fixed by #166