Update grammar to start with QueryUnit instead of query, and make Que…

…ry optional, to allow for empty input.

Rakefile

@@ -62,7 +62,7 @@ task :meta => "lib/sparql/grammar/meta.rb"
 
 file "lib/sparql/grammar/meta.rb" => "etc/sparql11.bnf" do |t|
   sh %{
-    ebnf --ll1 Query --format rb \
+    ebnf --ll1 QueryUnit --format rb \
       --mod-name SPARQL::Grammar::Meta \
       --output lib/sparql/grammar/meta.rb \
       etc/sparql11.bnf
@@ -71,7 +71,7 @@ end
 
 file "etc/sparql11.ll1.sxp" => "etc/sparql11.bnf" do |t|
   sh %{
-    ebnf --ll1 Query --format sxp \
+    ebnf --ll1 QueryUnit --format sxp \
       --output etc/sparql11.ll1.sxp \
       etc/sparql11.bnf
   }

etc/sparql11.bnf

@@ -1,6 +1,6 @@
 # SPARQL 1.1 Grammar
 
-    [1]   QueryUnit               ::= Query
+    [1]   QueryUnit               ::= Query?
     [2]   Query                   ::= Prologue
                                       ( SelectQuery | ConstructQuery | DescribeQuery | AskQuery )
                                       ValuesClause

etc/sparql11.ll1.sxp

@@ -1,10 +1,11 @@
 (
  (rule _empty "0" (first _eps) (seq))
  (rule QueryUnit "1"
-  (first "ASK" "BASE" "CONSTRUCT" "DESCRIBE" "PREFIX" "SELECT")
-  (seq Query))
- (rule Query "2"
   (start #t)
+  (first "ASK" "BASE" "CONSTRUCT" "DESCRIBE" "PREFIX" "SELECT" _eps)
+  (follow _eof)
+  (alt _empty Query))
+ (rule Query "2"
   (first "ASK" "BASE" "CONSTRUCT" "DESCRIBE" "PREFIX" "SELECT")
   (follow _eof)
   (seq Prologue _Query_1 ValuesClause))

etc/sparql11.sxp

@@ -1,6 +1,6 @@
 (
  (rule _empty "0" (seq))
- (rule QueryUnit "1" (seq Query))
+ (rule QueryUnit "1" (alt _empty Query))
  (rule Query "2" (seq Prologue _Query_1 ValuesClause))
  (rule _Query_1 "2.1" (alt SelectQuery ConstructQuery DescribeQuery AskQuery))
  (rule UpdateUnit "3" (seq Update))

lib/sparql/grammar/meta.rb

@@ -1,7 +1,7 @@
-# This file is automatically generated by /Users/gregg/.rvm/gems/ruby-1.9.3-p392/bundler/gems/ebnf-cd313e5f46b4/bin/ebnf
+# This file is automatically generated by /Users/gregg/.rvm/gems/ruby-1.9.3-p392/bundler/gems/ebnf-92bb7ca4b9c0/bin/ebnf
 # BRANCH derived from etc/sparql11.bnf
 module SPARQL::Grammar::Meta
-  START = :Query
+  START = :QueryUnit
 
   BRANCH = {
     :AdditiveExpression => {
@@ -4327,6 +4327,14 @@ module SPARQL::Grammar::Meta
       "PREFIX" => [:Prologue, :_Query_1, :ValuesClause],
       "SELECT" => [:Prologue, :_Query_1, :ValuesClause],
     },
+    :QueryUnit => {
+      "ASK" => [:Query],
+      "BASE" => [:Query],
+      "CONSTRUCT" => [:Query],
+      "DESCRIBE" => [:Query],
+      "PREFIX" => [:Query],
+      "SELECT" => [:Query],
+    },
     :_Query_1 => {
       "ASK" => [:AskQuery],
       "CONSTRUCT" => [:ConstructQuery],
@@ -13832,6 +13840,7 @@ module SPARQL::Grammar::Meta
       "BASE",
       "PREFIX"],
     :QueryUnit => [
+      :_eps,
       "CONSTRUCT",
       "DESCRIBE",
       "ASK",
@@ -40459,6 +40468,8 @@ module SPARQL::Grammar::Meta
       "GRAPH"],
     :Query => [
       :_eof],
+    :QueryUnit => [
+      :_eof],
     :_Query_1 => [
       "VALUES",
       :_eof],

lib/sparql/grammar/parser11.rb

@@ -1043,8 +1043,7 @@ def to_s
     def parse(prod = START)
       ll1_parse(@input, prod.to_sym, @options.merge(:branch => BRANCH,
                                                      :first => FIRST,
-                                                     :follow => FOLLOW)
-      ) {}
+                                                     :follow => FOLLOW))
 
       # The last thing on the @prod_data stack is the result
       @result = case

spec/grammar/parser_spec.rb

@@ -705,10 +705,18 @@ def bgp_patterns
   include ProductionRequirements
   include ProductionExamples
 
-  describe "when matching the [2] Query production rule" do
-    with_production(:Query) do |production|
+  describe "when matching the [1] QueryUnit production rule" do
+    with_production(:QueryUnit) do |production|
       it_ignores_empty_input_using production
+      given_it_generates(production, "SELECT * FROM <a> WHERE {?a ?b ?c}", %q((dataset (<a>) (bgp (triple ?a ?b ?c)))))
+      given_it_generates(production, "CONSTRUCT {?a ?b ?c} WHERE {?a ?b ?c FILTER (?a)}", %q((construct ((triple ?a ?b ?c)) (filter ?a (bgp (triple ?a ?b ?c))))))
+      given_it_generates(production, "DESCRIBE * FROM <a> WHERE {?a ?b ?c}", %q((describe () (dataset (<a>) (bgp (triple ?a ?b ?c))))))
+      given_it_generates(production, "ASK WHERE {GRAPH <a> {?a ?b ?c}}", %q((ask (graph <a> (bgp (triple ?a ?b ?c))))))
+    end
+  end
 
+  describe "when matching the [2] Query production rule" do
+    with_production(:Query) do |production|
       {
         "BASE <foo/> SELECT * WHERE { <a> <b> <c> }" =>
           %q((base <foo/> (bgp (triple <a> <b> <c>)))),
@@ -937,7 +945,6 @@ def bgp_patterns
 
   describe "when matching the [13] DatasetClause production rule" do
     with_production(:DatasetClause) do |production|
-      it_ignores_empty_input_using production
       given_it_generates(production, %q(FROM <http://example.org/foaf/aliceFoaf>), [:dataset, RDF::URI("http://example.org/foaf/aliceFoaf")])
       given_it_generates(production, %q(FROM NAMED <http://example.org/foaf/aliceFoaf>), [:dataset, [:named, RDF::URI("http://example.org/foaf/aliceFoaf")]])
     end
@@ -949,8 +956,6 @@ def bgp_patterns
   #   [16] SourceSelector
   describe "when matching the [17] WhereClause production rule" do
     with_production(:WhereClause) do |production|
-      it_ignores_empty_input_using production
-
       bgp_patterns.each_pair do |input, result|
         given_it_generates(production, "WHERE {#{input}}", result,
           :prefixes => {nil => "http://example.com/", :rdf => RDF.to_uri.to_s},
@@ -1238,7 +1243,6 @@ def bgp_patterns
   # [69] Constraint ::=  BrackettedExpression | BuiltInCall | FunctionCall
   describe "when matching the [69] Constraint production rule" do
     with_production(:Constraint) do |production|
-      it_ignores_empty_input_using production
       it_recognizes_bracketted_expression_using production
       it_recognizes_built_in_call_using production
       it_recognizes_function_using production
@@ -1341,8 +1345,6 @@ def bgp_patterns
 
     describe "when matching the [108] Var production rule" do
       with_production(:Var) do |production|
-        it_ignores_empty_input_using production
-
         it "recognizes the VAR1 terminal" do
           it_recognizes_var1(production)
         end