Fix increment/decrement tags to use a separate counter namespace

spec/integration/golden_liquid.pending

@@ -35,8 +35,6 @@ liquid.golden.date_filter timestamp integer
 liquid.golden.date_filter timestamp string
 liquid.golden.date_filter undefined argument
 liquid.golden.date_filter well formed string
-liquid.golden.decrement_tag increment and decrement named counter
-liquid.golden.decrement_tag named counter
 liquid.golden.default_filter missing argument
 liquid.golden.echo_tag access an array item by index
 liquid.golden.echo_tag access an array item by negative index
@@ -134,11 +132,6 @@ liquid.golden.include_tag some keyword arguments without leading comma
 liquid.golden.include_tag some keyword arguments with range literal
 liquid.golden.include_tag string literal name
 liquid.golden.include_tag use globals from outer scope
-liquid.golden.increment_tag assign and increment
-liquid.golden.increment_tag incrementing counter renders before incrementing
-liquid.golden.increment_tag multiple named counters
-liquid.golden.increment_tag named counter
-liquid.golden.increment_tag named counters are in scope for subsequent expressions
 liquid.golden.inline_comment_tag can't comment tags
 liquid.golden.inline_comment_tag empty
 liquid.golden.inline_comment_tag liquid tag

src/liquid/codegen_visitor.cr

@@ -154,5 +154,13 @@ module Liquid
       node.children.each &.accept self
       pop
     end
+
+    def visit(node : Increment)
+      to_io %(Liquid::Block::Increment.new("#{escape node.var_name}"))
+    end
+
+    def visit(node : Decrement)
+      to_io %(Liquid::Block::Decrement.new("#{escape node.var_name}"))
+    end
   end
 end

src/liquid/context.cr

@@ -19,6 +19,7 @@ module Liquid
     end
 
     @data : Hash(String, Any)
+    @counters = Hash(String, Int32).new(0)
 
     # :nodoc:
     # These values are used/reused when calling filters in a expression using this context.
@@ -80,12 +81,31 @@ module Liquid
       Any.new(nil)
     end
 
+    def increment_counter(name : String) : Int32
+      val = @counters[name]
+      @counters[name] = val + 1
+      val
+    end
+
+    def decrement_counter(name : String) : Int32
+      @counters[name] -= 1
+      @counters[name]
+    end
+
+    def counter(name : String) : Int32
+      @counters[name]
+    end
+
     # Fetch a variable from context, add `UndefinedVariable` error if the variable isn't found and behave according the
     # error mode.
     def get(var : String) : Any
       value = @data[var]?
       return value if value
 
+      if @counters.has_key?(var)
+        return Any.new(@counters[var])
+      end
+
       add_error(UndefinedVariable.new(var))
     end
 

src/liquid/render_visitor.cr

@@ -91,21 +91,11 @@ module Liquid
     end
 
     def visit(node : Increment)
-      var = @data.get node.var_name
-      if var && (num = var.as_i?)
-        @data.set node.var_name, num + 1
-      else
-        @data.set node.var_name, 1
-      end
+      @io << @data.increment_counter(node.var_name)
     end
 
     def visit(node : Decrement)
-      var = @data.get node.var_name
-      if var && (num = var.as_i?)
-        @data.set node.var_name, num - 1
-      else
-        @data.set node.var_name, -1
-      end
+      @io << @data.decrement_counter(node.var_name)
     end
 
     def visit(node : ExpressionNode)