vendored parslet, deemed stable enough and better without dependency

lib/parslet/error_reporter/deepest.rb

@@ -0,0 +1,95 @@
+module Parslet
+  module ErrorReporter
+    # Instead of reporting the latest error that happens like {Tree} does,
+    # this class reports the deepest error. Depth is defined here as how
+    # advanced into the input an error happens. The errors close to the
+    # greatest depth tend to be more relevant to the end user, since they
+    # specify what could be done to make them go away. 
+    #
+    # More specifically, errors produced by this reporter won't be related to
+    # the structure of the grammar at all. The positions of the errors will 
+    # be advanced and convey at every grammar level what the deepest rule
+    # was to fail. 
+    #
+    class Deepest
+      def initialize
+        @deepest_cause = nil
+      end
+      
+      # Produces an error cause that combines the message at the current level
+      # with the errors that happened at a level below (children).
+      #
+      # @param atom [Parslet::Atoms::Base] parslet that failed
+      # @param source [Source] Source that we're using for this parse. (line 
+      #   number information...)
+      # @param message [String, Array] Error message at this level.
+      # @param children [Array] A list of errors from a deeper level (or nil).
+      # @return [Cause] An error tree combining children with message.
+      #
+      def err(atom, source, message, children=nil)
+        position = source.pos
+        cause = Cause.format(source, position, message, children)
+        return deepest(cause)
+      end
+
+      # Produces an error cause that combines the message at the current level
+      # with the errors that happened at a level below (children).
+      #
+      # @param atom [Parslet::Atoms::Base] parslet that failed
+      # @param source [Source] Source that we're using for this parse. (line 
+      #   number information...)
+      # @param message [String, Array] Error message at this level.
+      # @param pos [Fixnum] The real position of the error.
+      # @param children [Array] A list of errors from a deeper level (or nil).
+      # @return [Cause] An error tree combining children with message.
+      #
+      def err_at(atom, source, message, pos, children=nil)
+        position = pos
+        cause = Cause.format(source, position, message, children)
+        return deepest(cause)
+      end
+      
+      # Returns the cause that is currently deepest. Mainly for specs. 
+      #
+      attr_reader :deepest_cause
+      
+      # Checks to see if the lineage of the cause given includes a cause with
+      # an error position deeper than the current deepest cause stored. If
+      # yes, it passes the cause through to the caller. If no, it returns the
+      # current deepest error that was saved as a reference.
+      #
+      def deepest(cause)
+        rank, leaf = deepest_child(cause)
+        
+        if !deepest_cause || leaf.pos >= deepest_cause.pos
+          # This error reaches deeper into the input, save it as reference.
+          @deepest_cause = leaf
+          return cause
+        end
+        
+        return deepest_cause
+      end
+      
+    private
+      # Returns the leaf from a given error tree with the biggest rank. 
+      #
+      def deepest_child(cause, rank=0)
+        max_child = cause
+        max_rank  = rank
+        
+        if cause.children && !cause.children.empty?
+          cause.children.each do |child|
+            c_rank, c_cause = deepest_child(child, rank+1)
+            
+            if c_rank > max_rank
+              max_rank = c_rank
+              max_child = c_cause
+            end
+          end
+        end
+        
+        return max_rank, max_child
+      end
+    end
+  end
+end

lib/parslet/error_reporter/tree.rb

@@ -0,0 +1,57 @@
+module Parslet
+  module ErrorReporter
+    # An error reporter has two central methods, one for reporting errors at
+    # the current parse position (#err) and one for reporting errors at a
+    # given parse position (#err_at). The reporter can return an object (a
+    # 'cause') that will be returned to the caller along with the information
+    # that the parse failed. 
+    # 
+    # When reporting errors on the outer levels of your parser, these methods
+    # get passed a list of error objects ('causes') from the inner levels. In
+    # this default implementation, the inner levels are considered error
+    # subtrees and are appended to the generated tree node at each level,
+    # thereby constructing an error tree. 
+    #
+    # This error tree will report in parallel with the grammar structure that
+    # failed. A one-to-one correspondence exists between each error in the 
+    # tree and the parslet atom that produced that error. 
+    #
+    # The implementor is really free to use these return values as he sees
+    # fit. One example would be to return an error state object from these
+    # methods that is then updated as errors cascade up the parse derivation
+    # tree. 
+    #
+    class Tree
+      # Produces an error cause that combines the message at the current level
+      # with the errors that happened at a level below (children).
+      #
+      # @param atom [Parslet::Atoms::Base] parslet that failed
+      # @param source [Source] Source that we're using for this parse. (line 
+      #   number information...)
+      # @param message [String, Array] Error message at this level.
+      # @param children [Array] A list of errors from a deeper level (or nil).
+      # @return [Cause] An error tree combining children with message.
+      #
+      def err(atom, source, message, children=nil)
+        position = source.pos
+        Cause.format(source, position, message, children)
+      end
+
+      # Produces an error cause that combines the message at the current level
+      # with the errors that happened at a level below (children).
+      #
+      # @param atom [Parslet::Atoms::Base] parslet that failed
+      # @param source [Source] Source that we're using for this parse. (line 
+      #   number information...)
+      # @param message [String, Array] Error message at this level.
+      # @param pos [Fixnum] The real position of the error.
+      # @param children [Array] A list of errors from a deeper level (or nil).
+      # @return [Cause] An error tree combining children with message.
+      #
+      def err_at(atom, source, message, pos, children=nil)
+        position = pos
+        Cause.format(source, position, message, children)
+      end
+    end
+  end
+end