Fix problems serializing list elements which are also the IRI subject…

…s of statements.

Improve whitespace.

lib/rdf/turtle/writer.rb

@@ -366,8 +366,8 @@ def order_subjects
           seen[st.object] if @lists.has_key?(st.object)
         end
 
-      # List elements should not be targets for top-level serialization
-      list_elements = @lists.values.map(&:to_a).flatten.compact
+        # List elements which are bnodes should not be targets for top-level serialization
+        list_elements = @lists.values.map(&:to_a).flatten.select(&:node?).compact
 
       # Sort subjects by resources over bnodes, ref_counts and the subject URI itself
       recursable = (@subjects.keys - list_elements).
@@ -504,12 +504,15 @@ def do_list(l, position)
       list = @lists[l]
       log_debug("do_list") {list.inspect}
       subject_done(RDF.nil)
+      index = 0
       list.each_statement do |st|
         next unless st.predicate == RDF.first
         log_debug {" list this: #{st.subject} first: #{st.object}[#{position}]"}
+        @output.write(" ") if index > 0
         path(st.object, position)
         subject_done(st.subject)
         position = :object
+        index += 1
       end
     end
 
@@ -519,7 +522,7 @@ def collection(node, position)
       return false if position == :object && prop_count(node) > 0
       #log_debug("collection") {"#{node.to_ntriples}, #{position}"}
 
-      @output.write(position == :subject ? "(" : " (")
+      @output.write("(")
       log_depth {do_list(node, position)}
       @output.write(')')
     end
@@ -530,16 +533,20 @@ def blankNodePropertyList(resource, position)
 
       log_debug("blankNodePropertyList") {resource.to_ntriples}
       subject_done(resource)
-      @output.write(position == :subject ? "\n#{indent} [" : ' [')
+      @output.write(position == :subject ? "\n#{indent} [" : '[')
       num_props = log_depth {predicateObjectList(resource, true)}
-      @output.write((num_props > 1 ? "\n#{indent}" : "") + (position == :object ? ']' : '] .'))
+      @output.write((num_props > 1 ? "\n#{indent(2)}" : "") + (position == :object ? ']' : '] .'))
       true
     end
 
     # Default singular resource representation.
     def p_term(resource, position)
       #log_debug("p_term") {"#{resource.to_ntriples}, #{position}"}
-      l = (position == :subject ? "" : " ") + format_term(resource, options)
+      l = if resource == RDF.nil
+        "()"
+      else
+        format_term(resource, options)
+      end
       @output.write(l)
     end
 
@@ -562,7 +569,7 @@ def path(resource, position)
     def predicate(resource)
       log_debug("predicate") {resource.to_ntriples}
       if resource == RDF.type
-        @output.write(" a")
+        @output.write("a")
       else
         path(resource, :predicate)
       end
@@ -601,6 +608,7 @@ def predicateObjectList(subject, from_bpl = false)
         begin
           @output.write(";\n#{indent(2)}") if i > 0
           predicate(RDF::URI.intern(prop))
+          @output.write(" ")
           objectList(properties[prop])
         end
       end
@@ -611,8 +619,9 @@ def predicateObjectList(subject, from_bpl = false)
     def triples(subject)
       @output.write("\n#{indent}")
       path(subject, :subject)
-      predicateObjectList(subject)
-      @output.write(" .")
+      @output.write(" ")
+      num_props = predicateObjectList(subject)
+      @output.write("#{num_props > 0 ? ' ' : ''}.")
       true
     end
 

spec/writer_spec.rb

@@ -90,7 +90,7 @@
       },
       "bare anon" => {
         input: %(@prefix ex: <http://example.com/> . [ex:a ex:b] .),
-        regexp: [%r(^\s*\[ ex:a ex:b\] \.$)],
+        regexp: [%r(^\s*\[ex:a ex:b\] \.$)],
         regexp_stream: [%r(_:\w+ ex:a ex:b \.$)]
       },
       "anon as subject" => {
@@ -106,7 +106,7 @@
       },
       "anon as object" => {
         input: %(@prefix ex: <http://example.com/> . ex:a ex:b [ex:c ex:d] .),
-        regexp: [%r(^ex:a ex:b \[ ex:c ex:d\] \.$)],
+        regexp: [%r(^ex:a ex:b \[ex:c ex:d\] \.$)],
         regexp_stream: []
       },
       "reuses BNode labels by default" => {
@@ -179,6 +179,14 @@
         input: %(@prefix ex: <http://example.com/> . [ex:twoAnons ([a ex:mother] [a ex:father])] .),
         regexp: [%r(\[\s*ex:twoAnons \(\s*\[\s*a ex:mother\s*\] \[\s*a ex:father\s*\]\)\] \.$)]
       },
+      "list subjects": {
+        input: %(@prefix ex: <http://example.com/> . (ex:a ex:b) . ex:a a ex:Thing . ex:b a ex:Thing .),
+        regexp: [
+          %r(\(ex:a ex:b\) \.),
+          %r(ex:a a ex:Thing \.),
+          %r(ex:b a ex:Thing \.),
+        ]
+      },
       "owl:unionOf list": {
         input: %(
           @prefix ex: <http://example.com/> .
@@ -531,24 +539,24 @@
           ], canonicalize: true)
         end
       end
-    end
 
-    [
-      [0, "0.0e0"],
-      [10, "1.0e1"],
-      [-1, "-1.0e0"],
-      ["0", "0.0e0"],
-      ["10", "1.0e1"],
-      ["-1", "-1.0e0"],
-      ["1.0", "1.0e0"],
-      ["0.1", "1.0e-1"],
-      ["10.01", "1.001e1"],
-      ["true", %{"true"^^<http://www.w3.org/2001/XMLSchema#double>}],
-      ["false", %{"false"^^<http://www.w3.org/2001/XMLSchema#double>}],
-      ["string", %{"string"^^<http://www.w3.org/2001/XMLSchema#double>}],
-    ].each do |(l,r)|
-      it "serializes #{l.inspect} to #{r.inspect}" do
-        expect(subject.format_literal(RDF::Literal::Double.new(l))).to eql r
+      [
+        [0, "0.0e0"],
+        [10, "1.0e1"],
+        [-1, "-1.0e0"],
+        ["0", "0.0e0"],
+        ["10", "1.0e1"],
+        ["-1", "-1.0e0"],
+        ["1.0", "1.0e0"],
+        ["0.1", "1.0e-1"],
+        ["10.01", "1.001e1"],
+        ["true", %{"true"^^<http://www.w3.org/2001/XMLSchema#double>}],
+        ["false", %{"false"^^<http://www.w3.org/2001/XMLSchema#double>}],
+        ["string", %{"string"^^<http://www.w3.org/2001/XMLSchema#double>}],
+      ].each do |(l,r)|
+        it "serializes #{l.inspect} to #{r.inspect}" do
+          expect(subject.format_literal(RDF::Literal::Double.new(l))).to eql r
+        end
       end
     end