show-doc for core classes now shows file name, closes #536

lib/pry/default_commands/introspection.rb

@@ -54,17 +54,29 @@ class Pry
           klass = target.eval(name)
 
           mod = Pry::WrappedModule(klass)
-          file_name, line = mod.source_location
+
+          # source_file reveals the underlying .c file in case of core
+          # classes on MRI.
+          # This is different to source_location, which
+          # will return nil.
+          if mod.yard_docs?
+            file_name, line = mod.source_file, nil
+          else
+            file_name, line = mod.source_location
+          end
+
           doc = mod.doc
 
           if doc.empty?
             output.puts "No documentation found."
           else
-            set_file_and_dir_locals(file_name)
+
+            # source_location is nil in case of core classes on MRI
+            set_file_and_dir_locals(file_name) if !mod.yard_docs?
             output.puts "\n#{Pry::Helpers::Text.bold('From:')} #{file_name} @ line #{line}:\n\n"
 
             if opts.present?(:b) || opts.present?(:l)
-              start_line = file_name.nil? ? 1 : line - doc.lines.count
+              start_line = mod.source_location.nil? ? 1 : line - doc.lines.count
               doc = Code.new(doc, start_line, :text).
                 with_line_numbers(true)
             end

lib/pry/wrapped_module.rb

@@ -101,17 +101,20 @@ class Pry
       super || wrapped.respond_to?(method_name)
     end
 
+    def yard_docs?
+      !!(defined?(YARD) && YARD::Registry.at(name))
+    end
+
     def doc
       return @doc if @doc
 
       file_name, line = source_location
 
-      if file_name.nil?
-        if defined?(YARD) && from_yard = YARD::Registry.at(name)
-          @doc = from_yard.docstring
-        else
-          raise CommandError, "Can't find module's source location"
-        end
+      if yard_docs?
+        from_yard = YARD::Registry.at(name)
+        @doc = from_yard.docstring
+      elsif source_location.nil?
+        raise CommandError, "Can't find module's source location"
       else
         @doc = extract_doc
       end
@@ -132,6 +135,19 @@ class Pry
 
     end
 
+    def source_file
+      if yard_docs?
+        from_yard = YARD::Registry.at(name)
+        from_yard.file
+      else
+        Array(source_location).first
+      end
+    end
+
+    def source_line
+      source_location.nil? ? nil : source_location.last
+    end
+
     # Retrieve the source location of a module. Return value is in same
     # format as Method#source_location. If the source location
     # cannot be found this method returns `nil`.