Adding mapping filter to JsonQuery.

lib/json_query.rb

@@ -227,8 +227,14 @@ def _nt_filter
         r0 = r2
         r0.extend(Filter)
       else
-        self.index = i0
-        r0 = nil
+        r3 = _nt_map_filter
+        if r3
+          r0 = r3
+          r0.extend(Filter)
+        else
+          self.index = i0
+          r0 = nil
+        end
       end
     end
 
@@ -488,6 +494,57 @@ def _nt_boolean_filter
     return r0
   end
 
+  module MapFilter0
+    def expression
+      elements[1]
+    end
+
+  end
+
+  def _nt_map_filter
+    start_index = index
+    if node_cache[:map_filter].has_key?(index)
+      cached = node_cache[:map_filter][index]
+      @index = cached.interval.end if cached
+      return cached
+    end
+
+    i0, s0 = index, []
+    if input.index("[=", index) == index
+      r1 = (SyntaxNode).new(input, index...(index + 2))
+      @index += 2
+    else
+      terminal_parse_failure("[=")
+      r1 = nil
+    end
+    s0 << r1
+    if r1
+      r2 = _nt_expression
+      s0 << r2
+      if r2
+        if input.index("]", index) == index
+          r3 = (SyntaxNode).new(input, index...(index + 1))
+          @index += 1
+        else
+          terminal_parse_failure("]")
+          r3 = nil
+        end
+        s0 << r3
+      end
+    end
+    if s0.last
+      r0 = (MapFilter).new(input, i0...index, s0)
+      r0.extend(MapFilter0)
+    else
+      self.index = i0
+      r0 = nil
+    end
+
+    node_cache[:map_filter][start_index] = r0
+
+    return r0
+  end
+
   def _nt_boolean_expression
     start_index = index
     if node_cache[:boolean_expression].has_key?(index)

lib/json_query.tt

@@ -24,7 +24,7 @@ grammar JsonQuery
   end
 
   rule filter
-    (field_access / boolean_filter) <Filter>
+    (field_access / boolean_filter / map_filter) <Filter>
   end
 
   rule field_access
@@ -43,6 +43,10 @@ grammar JsonQuery
     "[?" boolean_expression "]" <BooleanFilter>
   end
 
+  rule map_filter
+    "[=" expression "]" <MapFilter>
+  end
+
   rule boolean_expression
     or_expression / and_expression / boolean_atom
   end

lib/json_query/nodes.rb

@@ -84,6 +84,14 @@ def value(list, root, symbols, current = nil)
     end
   end
 
+  class MapFilter < Treetop::Runtime::SyntaxNode
+    def value(list, root, symbols, current = nil)
+      list.map do |object|
+        expression.value(root, symbols, object)
+      end
+    end
+  end
+
   class And < Treetop::Runtime::SyntaxNode
     def value(root, symbols, current = nil)
       first.value(root, symbols, current) && second.value(root, symbols, current)

test/test_siren.rb

@@ -101,6 +101,9 @@ def test_json_query
 
     assert_equal ["Sayings of the Century", "The Lord of the Rings"],
         Siren.query("$.store.book[0,3]", fixtures(:store)).map { |b| b["title"] }
+
+    assert_equal fixtures(:store)["store"]["book"].map { |b| b["title"] },
+        Siren.query("$.store.book[= @.title ]", fixtures(:store))
   end
 end