Add :rdf_star option on Turtle/TriG encoder

CHANGELOG.md

@@ -18,19 +18,21 @@ Elixir v1.15 or later, where this issue has been resolved.
 ### Added
 
 - `RDF.TriG` with an implementation of the TriG serialization language. 
-- Capability to add custom content on the Turtle/TriG encoders with the `:content` option.
-- Option `:line_prefix` on Turtle/TriG encoder for a function defining custom line prefixes.
-- Option `:indent_width` on Turtle/TriG encoder to customize the indentation width.
-- Option `:pn_local_validation` on Turtle/TriG encoder for controlling IRI validation 
-  when encoding as a prefixed name.
+- Several new options on the Turtle/TriG encoder for more customizations and 
+  performance optimizations:
+  - Capability to add custom content on the Turtle/TriG encoders with the `:content` option.
+  - `:line_prefix` for a function defining custom line prefixes
+  - `:indent_width` to customize the indentation width
+  - `:pn_local_validation` for controlling IRI validation when encoding prefixed names
+  - `:rdf_star` allowing to skip an RDF-star related preprocessing step
 - `RDF.Dataset.update_all_graphs/2` to apply a function on all graphs of a dataset.
 - `RDF.Dataset.named_graphs/1` to get a list of all named graphs of a dataset.
 - `RDF.Dataset.graph_names/1` to get a list of all graph names of a dataset.
+- `RDF.Graph.prefixes/2` which allows to specify a custom return value when the prefixes 
+  are empty.
 - `RDF.PrefixMap.empty?/1` to check of a `RDF.PrefixMap` is empty.
 - `RDF.PrefixMap.limit/2` to limit a `RDF.PrefixMap` to a subset of some given prefixes.
 - Performance improvements of N-Triples and N-Quads encoders.
-- `RDF.Graph.prefixes/2` which allows to specify a custom return value when the prefixes 
-  are empty.
 
 ### Changed
 

lib/rdf/serializations/turtle_trig/encoder.ex

@@ -70,6 +70,9 @@ defmodule RDF.TurtleTriG.Encoder do
       - Note: Currently, a `:strict` mode, which would provide comprehensive validation
         conforming strictly to the Turtle specification, is not implemented.
         Contributions for implementing this mode are welcome.
+    - `:rdf_star`: Allows to skip a RDF-star related preprocessing step. This can be
+       used to improve performance a little bit when you know the encoded data doesn't
+       include any RDF-star statements. Defaults to the returned value of `RDF.star?/0`.
     """
   end
 
@@ -189,7 +192,7 @@ defmodule RDF.TurtleTriG.Encoder do
 
   defp graph_statements(%{single_triple_lines: true} = state) do
     state.graph
-    |> CompactStarGraph.compact()
+    |> CompactStarGraph.compact(state.rdf_star)
     |> Sequencer.descriptions(State.base_iri(state))
     |> Enum.map(
       &(&1
@@ -202,7 +205,7 @@ defmodule RDF.TurtleTriG.Encoder do
 
   defp graph_statements(state) do
     state.graph
-    |> CompactStarGraph.compact()
+    |> CompactStarGraph.compact(state.rdf_star)
     |> Sequencer.descriptions(State.base_iri(state))
     |> Enum.map(&(&1 |> description_statements(state) |> indented(state)))
     |> Enum.reject(&Enum.empty?/1)

lib/rdf/serializations/turtle_trig/encoder/compact_star_graph.ex

@@ -8,7 +8,9 @@ defmodule RDF.TurtleTriG.Encoder.CompactStarGraph do
 
   alias RDF.{Graph, Description}
 
-  def compact(graph) do
+  def compact(graph, false), do: graph
+
+  def compact(graph, true) do
     Enum.reduce(graph.descriptions, graph, fn
       {{_, _, _} = quoted_triple, _}, compact_graph ->
         # First check the original graph to see if the quoted triple is asserted.

lib/rdf/serializations/turtle_trig/encoder/state.ex

@@ -14,7 +14,8 @@ defmodule RDF.TurtleTriG.Encoder.State do
     :base_indent,
     :indentation,
     :indent_step,
-    :bnode_info
+    :bnode_info,
+    :rdf_star
   ]
 
   @default_indent_width 4
@@ -49,7 +50,8 @@ defmodule RDF.TurtleTriG.Encoder.State do
       indent_step: opts |> Keyword.get(:indent_width, @default_indent_width) |> indent_string(),
       line_prefix: line_prefix,
       single_triple_lines: !!line_prefix || Keyword.get(opts, :single_triple_lines),
-      bnode_info: BnodeInfo.new(data)
+      bnode_info: BnodeInfo.new(data),
+      rdf_star: Keyword.get(opts, :rdf_star, RDF.star?())
     }
     |> init_indentation()
   end

test/unit/serializations/turtle_encoder_test.exs

@@ -809,6 +809,18 @@ defmodule RDF.Turtle.EncoderTest do
     # a case with RDF-star annotations in tested also in turtle_star_encoder_test.exs
   end
 
+  test ":rdf_star option" do
+    graph =
+      Graph.new([
+        {EX.S1, EX.p1(), EX.O1},
+        {EX.S1, EX.p2(), 42},
+        {EX.S2, EX.p3(), ~B<foo>}
+      ])
+
+    assert Turtle.Encoder.encode!(graph, rdf_star: false) ==
+             Turtle.Encoder.encode!(graph, rdf_star: true)
+  end
+
   %{
     "full IRIs without base" => %{
       input: "<http://a/b> <http://a/c> <http://a/d> .",