Prism::Node#tunnel

Author: kddnewton

lib/prism/node_ext.rb

@@ -172,7 +172,7 @@ def child
         DEPRECATED: ConstantPathNode#child is deprecated and will be removed \
         in the next major version. Use \
         ConstantPathNode#name/ConstantPathNode#name_loc instead. Called from \
-        #{caller(1..1).first}.
+        #{caller(1, 1)&.first}.
       MSG
 
       name ? ConstantReadNode.new(source, name, name_loc) : MissingNode.new(source, location)
@@ -214,7 +214,7 @@ def child
         DEPRECATED: ConstantPathTargetNode#child is deprecated and will be \
         removed in the next major version. Use \
         ConstantPathTargetNode#name/ConstantPathTargetNode#name_loc instead. \
-        Called from #{caller(1..1).first}.
+        Called from #{caller(1, 1)&.first}.
       MSG
 
       name ? ConstantReadNode.new(source, name, name_loc) : MissingNode.new(source, location)

lib/prism/pattern.rb

@@ -149,7 +149,10 @@ def compile_constant_path_node(node)
       parent = node.parent
 
       if parent.is_a?(ConstantReadNode) && parent.slice == "Prism"
-        compile_constant_name(node, node.name)
+        name = node.name
+        raise CompilationError, node.inspect if name.nil?
+
+        compile_constant_name(node, name)
       else
         compile_error(node)
       end

sig/prism/_private/pattern.rbs

@@ -15,6 +15,7 @@ module Prism
     def compile_alternation_pattern_node: (AlternationPatternNode) -> Proc
     def compile_constant_path_node: (ConstantPathNode) -> Proc
     def compile_constant_read_node: (ConstantReadNode) -> Proc
+    def compile_constant_name: (Prism::node, Symbol) -> Proc
     def compile_hash_pattern_node: (HashPatternNode) -> Proc
     def compile_nil_node: (NilNode) -> Proc
     def compile_regular_expression_node: (RegularExpressionNode) -> Proc

templates/lib/prism/node.rb.erb

@@ -76,6 +76,43 @@ module Prism
       DotVisitor.new.tap { |visitor| accept(visitor) }.to_dot
     end
 
+    # Returns a list of nodes that are descendants of this node that contain the
+    # given line and column. This is useful for locating a node that is selected
+    # based on the line and column of the source code.
+    #
+    # Important to note is that the column given to this method should be in
+    # bytes, as opposed to characters or code units.
+    def tunnel(line, column)
+      queue = [self]
+      result = []
+
+      while (node = queue.shift)
+        result << node
+
+        node.compact_child_nodes.each do |child_node|
+          child_location = child_node.location
+
+          start_line = child_location.start_line
+          end_line = child_location.end_line
+
+          if start_line == end_line
+            if line == start_line && column >= child_location.start_column && column < child_location.end_column
+              queue << child_node
+              break
+            end
+          elsif (line == start_line && column >= child_location.start_column) || (line == end_line && column < child_location.end_column)
+            queue << child_node
+            break
+          elsif line > start_line && line < end_line
+            queue << child_node
+            break
+          end
+        end
+      end
+
+      result
+    end
+
     # Returns a list of the fields that exist for this node class. Fields
     # describe the structure of the node. This kind of reflection is useful for
     # things like recursively visiting each node _and_ field in the tree.

templates/rbi/prism/node.rbi.erb

@@ -31,6 +31,9 @@ class Prism::Node
   sig { returns(String) }
   def to_dot; end
 
+  sig { params(line: Integer, column: Integer).returns(T::Array[Prism::Node]) }
+  def tunnel(line, column); end
+
   sig { abstract.params(visitor: Prism::Visitor).returns(T.untyped) }
   def accept(visitor); end
 

templates/sig/prism/node.rbs.erb

@@ -18,6 +18,7 @@ module Prism
     def slice_lines: () -> String
     def pretty_print: (untyped q) -> untyped
     def to_dot: () -> String
+    def tunnel: (Integer line, Integer column) -> Array[Prism::node]
   end
 
   type node_singleton = singleton(Node) & _NodeSingleton

test/prism/ruby_api_test.rb

@@ -266,6 +266,25 @@ def test_node_equality
       refute_operator parse_expression(complex_source_1), :===, parse_expression(complex_source_2)
     end
 
+    def test_node_tunnel
+      program = Prism.parse("foo(1) +\n  bar(2, 3) +\n  baz(3, 4, 5)").value
+
+      tunnel = program.tunnel(1, 4).last
+      assert_kind_of IntegerNode, tunnel
+      assert_equal 1, tunnel.value
+
+      tunnel = program.tunnel(2, 6).last
+      assert_kind_of IntegerNode, tunnel
+      assert_equal 2, tunnel.value
+
+      tunnel = program.tunnel(3, 9).last
+      assert_kind_of IntegerNode, tunnel
+      assert_equal 4, tunnel.value
+
+      tunnel = program.tunnel(3, 8)
+      assert_equal [ProgramNode, StatementsNode, CallNode, ArgumentsNode, CallNode, ArgumentsNode], tunnel.map(&:class)
+    end
+
     private
 
     def parse_expression(source)