Prioritise commands by match_score [Fixes #471]

lib/pry/command.rb

@@ -83,6 +83,30 @@ class Pry
         command_regex =~ val
       end
 
+      # How well does this command match the given line?
+      #
+      # Higher scores are better because they imply that this command matches
+      # the line more closely.
+      #
+      # The score is calculated by taking the number of characters at the start
+      # of the string that are used only to identify the command, not as part of
+      # the arguments.
+      #
+      # @example
+      #   /\.(.*)/.match_score(".foo") #=> 1
+      #   /\.*(.*)/.match_score("...foo") #=> 3
+      #   'hi'.match_score("hi there") #=> 2
+      #
+      # @param String  a line input at the REPL
+      # @return Fixnum
+      def match_score(val)
+        if command_regex =~ val
+          Regexp.last_match.size > 1 ? Regexp.last_match.begin(1) : Regexp.last_match.end(0)
+        else
+          -1
+        end
+      end
+
       # Store hooks to be run before or after the command body.
       # @see {Pry::CommandSet#before_command}
       # @see {Pry::CommandSet#after_command}

lib/pry/command_set.rb

@@ -281,7 +281,7 @@ class Pry
     # @param [String]  the line that may be a command invocation
     # @return [Pry::Command, nil]
     def find_command(val)
-      commands.values.detect{ |c| c.matches?(val) }
+      commands.values.select{ |c| c.matches?(val) }.sort_by{ |c| c.match_score(val) }.last
     end
 
     # Is the given line a command invocation?

test/test_command_set.rb

@@ -471,6 +471,18 @@ describe Pry::CommandSet do
       @set.find_command('colon').should == cmd
       Pry.config.command_prefix = ''
     end
+
+    it "should find the command that has the longest match" do
+      cmd = @set.command(/\.(.*)/){ }
+      cmd2 = @set.command(/\.\|\|(.*)/){ }
+      @set.find_command('.||').should == cmd2
+    end
+
+    it "should find the command that has the longest name" do
+      cmd = @set.command(/\.(.*)/){ }
+      cmd2 = @set.command('.||'){ }
+      @set.find_command('.||').should == cmd2
+    end
   end
 
   describe '.valid_command?' do