From c2e6ffdebba902a59f51d9c5e20416adabf4c178 Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Sat, 30 Mar 2019 22:11:04 +0100
Subject: [PATCH] Optimize RDF.PrefixMap.new/1 creation from another PrefixMap

---
 lib/rdf/prefix_map.ex         | 2 ++
 test/unit/prefix_map_test.exs | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/lib/rdf/prefix_map.ex b/lib/rdf/prefix_map.ex
index 68981b6..d596285 100644
--- a/lib/rdf/prefix_map.ex
+++ b/lib/rdf/prefix_map.ex
@@ -23,6 +23,8 @@ defmodule RDF.PrefixMap do
   """
   def new(map)
 
+  def new(%__MODULE__{} = prefix_map), do: prefix_map
+
   def new(map) when is_map(map) do
     %__MODULE__{map: Map.new(map, &normalize/1)}
   end
diff --git a/test/unit/prefix_map_test.exs b/test/unit/prefix_map_test.exs
index 595dc80..9c8d7bd 100644
--- a/test/unit/prefix_map_test.exs
+++ b/test/unit/prefix_map_test.exs
@@ -45,6 +45,10 @@ defmodule RDF.PrefixMapTest do
              ) == @example2
     end
 
+    test "with another prefix map" do
+      assert PrefixMap.new(@example2) == @example2
+    end
+
     test "when the IRI namespace is given as a RDF.Vocabulary.Namespace" do
       assert PrefixMap.new(
                ex1: "http://example.com/foo/",