Extract object path resolution into a class

5 files changed, 93 insertions, 69 deletions

diff --git a/lib/pry.rb b/lib/pry.rb
index 9a79d8e1..2b1460be 100644
--- a/lib/pry.rb
+++ b/lib/pry.rb
@@ -169,3 +169,4 @@ require "pry/indent"
 require "pry/last_exception"
 require "pry/prompt"
 require "pry/inspector"
+require 'pry/object_path'
diff --git a/lib/pry/commands/cd.rb b/lib/pry/commands/cd.rb
index b628176e..8e8cddb3 100644
--- a/lib/pry/commands/cd.rb
+++ b/lib/pry/commands/cd.rb
@@ -21,7 +21,8 @@ class Pry
 
     def process
       state.old_stack ||= []
-      stack, state.old_stack = context_from_object_path(arg_string, _pry_, state.old_stack)
+      stack, state.old_stack =
+        ObjectPath.new(arg_string, _pry_.binding_stack, state.old_stack).resolve
       _pry_.binding_stack = stack if stack
     end
   end
diff --git a/lib/pry/helpers/base_helpers.rb b/lib/pry/helpers/base_helpers.rb
index 771535a8..b4b3f13d 100644
--- a/lib/pry/helpers/base_helpers.rb
+++ b/lib/pry/helpers/base_helpers.rb
@@ -119,73 +119,6 @@ class Pry
 
         Pry::Pager.page(text, out)
       end
-
-      # @param [String] arg_string The object path expressed as a string.
-      # @param [Pry] _pry_ The relevant Pry instance.
-      # @param [Array<Binding>] old_stack The state of the old binding stack
-      # @return [Array<Array<Binding>, Array<Binding>>] An array
-      #   containing two elements: The new `binding_stack` and the old `binding_stack`.
-      def context_from_object_path(arg_string, _pry_=nil, old_stack=[])
-
-        # Extract command arguments. Delete blank arguments like " ", but
-        # don't delete empty strings like "".
-        path      = arg_string.split(/\//).delete_if { |a| a =~ /\A\s+\z/ }
-        stack     = _pry_.binding_stack.dup
-        state_old_stack = old_stack
-
-        # Special case when we only get a single "/", return to root.
-        if path.empty?
-          state_old_stack = stack.dup unless old_stack.empty?
-          stack = [stack.first]
-        end
-
-        path.each_with_index do |context, i|
-          begin
-            case context.chomp
-            when ""
-              state_old_stack = stack.dup
-              stack = [stack.first]
-            when "::"
-              state_old_stack = stack.dup
-              stack.push(TOPLEVEL_BINDING)
-            when "."
-              next
-            when ".."
-              unless stack.size == 1
-                # Don't rewrite old_stack if we're in complex expression
-                # (e.g.: `cd 1/2/3/../4).
-                state_old_stack = stack.dup if path.first == ".."
-                stack.pop
-              end
-            when "-"
-              unless old_stack.empty?
-                # Interchange current stack and old stack with each other.
-                stack, state_old_stack = state_old_stack, stack
-              end
-            else
-              state_old_stack = stack.dup if i == 0
-              stack.push(Pry.binding_for(stack.last.eval(context)))
-            end
-
-          rescue RescuableException => e
-            # Restore old stack to its initial values.
-            state_old_stack = old_stack
-
-            msg = [
-              "Bad object path: #{arg_string}.",
-              "Failed trying to resolve: #{context}.",
-              e.inspect
-            ].join(' ')
-
-            CommandError.new(msg).tap do |err|
-              err.set_backtrace e.backtrace
-              raise err
-            end
-          end
-        end
-        return stack, state_old_stack
-      end
-
     end
   end
 end
diff --git a/lib/pry/input_completer.rb b/lib/pry/input_completer.rb
index 74a249f9..86f9abf0 100644
--- a/lib/pry/input_completer.rb
+++ b/lib/pry/input_completer.rb
@@ -60,7 +60,7 @@ class Pry::InputCompleter
     if path.call.empty?
       target = options[:target]
     else
-      target, _ = Pry::Helpers::BaseHelpers.context_from_object_path(path.call, @pry)
+      target, _ = Pry::ObjectPath.new(path.call, @pry.binding_stack).resolve
       target = target.last
     end
 
diff --git a/lib/pry/object_path.rb b/lib/pry/object_path.rb
new file mode 100644
index 00000000..b669d3ec
--- /dev/null
+++ b/lib/pry/object_path.rb
@@ -0,0 +1,89 @@
+class Pry
+  # `ObjectPath` implements the resolution of "object paths", which are strings
+  # that are similar to filesystem paths but meant for traversing Ruby objects.
+  # Examples of valid object paths include:
+  #
+  #     x
+  #     @foo/@bar
+  #     "string"/upcase
+  #     Pry/Method
+  #
+  # Object paths are mostly relevant in the context of the `cd` command.
+  # @see https://github.com/pry/pry/wiki/State-navigation
+  class ObjectPath
+    # @param [String] path_string The object path expressed as a string.
+    # @param [Array<Binding>] current_stack The current state of the binding
+    #   stack.
+    # @param [Array<Binding>] old_stack The previous state of the binding
+    #   stack, if applicable.
+    def initialize(path_string, current_stack, old_stack=[])
+      @path_string   = path_string
+      @current_stack = current_stack
+      @old_stack     = old_stack
+    end
+
+    # @return [Array(Array<Binding>, Array<Binding>)] an array
+    #   containing two elements, the new binding stack and the old binding
+    #   stack.
+    def resolve
+      # Extract command arguments. Delete blank arguments like " ", but
+      # don't delete empty strings like "".
+      path      = @path_string.split(/\//).delete_if { |a| a =~ /\A\s+\z/ }
+      stack     = @current_stack.dup
+      state_old_stack = @old_stack
+
+      # Special case when we only get a single "/", return to root.
+      if path.empty?
+        state_old_stack = stack.dup unless @old_stack.empty?
+        stack = [stack.first]
+      end
+
+      path.each_with_index do |context, i|
+        begin
+          case context.chomp
+          when ""
+            state_old_stack = stack.dup
+            stack = [stack.first]
+          when "::"
+            state_old_stack = stack.dup
+            stack.push(TOPLEVEL_BINDING)
+          when "."
+            next
+          when ".."
+            unless stack.size == 1
+              # Don't rewrite old_stack if we're in complex expression
+              # (e.g.: `cd 1/2/3/../4).
+              state_old_stack = stack.dup if path.first == ".."
+              stack.pop
+            end
+          when "-"
+            unless @old_stack.empty?
+              # Interchange current stack and old stack with each other.
+              stack, state_old_stack = state_old_stack, stack
+            end
+          else
+            state_old_stack = stack.dup if i == 0
+            stack.push(Pry.binding_for(stack.last.eval(context)))
+          end
+
+        rescue RescuableException => e
+          # Restore old stack to its initial values.
+          state_old_stack = @old_stack
+
+          msg = [
+            "Bad object path: #{@path_string}.",
+            "Failed trying to resolve: #{context}.",
+            e.inspect
+          ].join(' ')
+
+          CommandError.new(msg).tap do |err|
+            err.set_backtrace e.backtrace
+            raise err
+          end
+        end
+      end
+
+      [stack, state_old_stack]
+    end
+  end
+end