Allow user to specify AST node prefix or suffix

Add ast_prefix and ast_suffix grammar statements.

lib/propane/generator.rb

@@ -120,7 +120,7 @@ class Propane
       end
       determine_possibly_empty_rulesets!(rule_sets)
       rule_sets.each do |name, rule_set|
-        rule_set.finalize
+        rule_set.finalize(@grammar)
       end
       # Generate the lexer.
       @lexer = Lexer.new(@grammar)

lib/propane/grammar.rb

@@ -6,6 +6,8 @@ class Propane
     IDENTIFIER_REGEX = /(?:[a-zA-Z]|_[a-zA-Z0-9])[a-zA-Z_0-9]*/
 
     attr_reader :ast
+    attr_reader :ast_prefix
+    attr_reader :ast_suffix
     attr_reader :modulename
     attr_reader :patterns
     attr_reader :rules
@@ -26,6 +28,8 @@ class Propane
       @ptypes = {"default" => "void *"}
       @prefix = "p_"
       @ast = false
+      @ast_prefix = ""
+      @ast_suffix = ""
       parse_grammar!
     end
 
@@ -54,6 +58,8 @@ class Propane
       elsif parse_comment_line!
       elsif @mode.nil? && parse_mode_label!
       elsif parse_ast_statement!
+      elsif parse_ast_prefix_statement!
+      elsif parse_ast_suffix_statement!
       elsif parse_module_statement!
       elsif parse_ptype_statement!
       elsif parse_pattern_statement!
@@ -91,6 +97,18 @@ class Propane
       end
     end
 
+    def parse_ast_prefix_statement!
+      if md = consume!(/ast_prefix\s+(\w+)\s*;/)
+        @ast_prefix = md[1]
+      end
+    end
+
+    def parse_ast_suffix_statement!
+      if md = consume!(/ast_suffix\s+(\w+)\s*;/)
+        @ast_suffix = md[1]
+      end
+    end
+
     def parse_module_statement!
       if consume!(/module\s+/)
         md = consume!(/([\w.]+)\s*/, "expected module name")

lib/propane/rule_set.rb

@@ -3,6 +3,10 @@ class Propane
   # A RuleSet collects all grammar rules of the same name.
   class RuleSet
 
+    # @return [Array<Hash>]
+    #   AST fields.
+    attr_reader :ast_fields
+
     # @return [Integer]
     #   ID of the RuleSet.
     attr_reader :id
@@ -76,6 +80,13 @@ class Propane
       @_start_token_set
     end
 
+    # Finalize a RuleSet after adding all Rules to it.
+    def finalize(grammar)
+      build_ast_fields(grammar)
+    end
+
+    private
+
     # Build the set of AST fields for this RuleSet.
     #
     # This is an Array of Hashes. Each entry in the Array corresponds to a
@@ -84,46 +95,38 @@ class Propane
     # a key. It may also have the field name without the positional suffix if
     # that field only exists in one position across all Rules in the RuleSet.
     #
-    # @return [Array<Hash>]
-    #   AST fields.
-    def ast_fields
-      @_ast_fields ||=
-        begin
-          field_ast_node_indexes = {}
-          field_indexes_across_all_rules = {}
-          ast_node_fields = []
-          @rules.each do |rule|
-            rule.components.each_with_index do |component, i|
-              if component.is_a?(Token)
-                node_name = "Token"
-              else
-                node_name = component.name
-              end
-              field_name = "p#{node_name}#{i + 1}"
-              unless field_ast_node_indexes[field_name]
-                field_ast_node_indexes[field_name] = ast_node_fields.size
-                ast_node_fields << {field_name => node_name}
-              end
-              field_indexes_across_all_rules[node_name] ||= Set.new
-              field_indexes_across_all_rules[node_name] << field_ast_node_indexes[field_name]
-              rule.rule_set_node_field_index_map[i] = field_ast_node_indexes[field_name]
-            end
+    # @return [void]
+    def build_ast_fields(grammar)
+      field_ast_node_indexes = {}
+      field_indexes_across_all_rules = {}
+      @ast_fields = []
+      @rules.each do |rule|
+        rule.components.each_with_index do |component, i|
+          if component.is_a?(Token)
+            node_name = "Token"
+          else
+            node_name = component.name
           end
-          field_indexes_across_all_rules.each do |node_name, indexes_across_all_rules|
-            if indexes_across_all_rules.size == 1
-              # If this field was only seen in one position across all rules,
-              # then add an alias to the positional field name that does not
-              # include the position.
-              ast_node_fields[indexes_across_all_rules.first]["p#{node_name}"] = node_name
-            end
+          struct_name = "#{grammar.ast_prefix}#{node_name}#{grammar.ast_suffix}"
+          field_name = "p#{node_name}#{i + 1}"
+          unless field_ast_node_indexes[field_name]
+            field_ast_node_indexes[field_name] = @ast_fields.size
+            @ast_fields << {field_name => struct_name}
           end
-          ast_node_fields
+          field_indexes_across_all_rules[node_name] ||= Set.new
+          field_indexes_across_all_rules[node_name] << field_ast_node_indexes[field_name]
+          rule.rule_set_node_field_index_map[i] = field_ast_node_indexes[field_name]
         end
-    end
-
-    # Finalize a RuleSet after adding all Rules to it.
-    def finalize
-      ast_fields
+      end
+      field_indexes_across_all_rules.each do |node_name, indexes_across_all_rules|
+        if indexes_across_all_rules.size == 1
+          # If this field was only seen in one position across all rules,
+          # then add an alias to the positional field name that does not
+          # include the position.
+          @ast_fields[indexes_across_all_rules.first]["p#{node_name}"] =
+            "#{grammar.ast_prefix}#{node_name}#{grammar.ast_suffix}"
+        end
+      end
     end
 
   end