add support for embed retain placeholder string

Author: jhchen

lib/delta/op.ex

@@ -242,6 +242,19 @@ defmodule Delta.Op do
   @spec get_embed_data!(map, map) :: {any, any, any}
   def get_embed_data!(a, b) do
     cond do
+      a == "\n" and is_map(b) and map_size(b) == 1 ->
+        [type] = Map.keys(b)
+
+        empty =
+          case b[type] do
+            %{} -> %{}
+            value when is_list(value) -> []
+            "" <> _ -> ""
+            _ -> nil
+          end
+
+        {type, empty, b[type]}
+
       not is_map(a) ->
         raise("cannot retain #{inspect(a)}")
 

test/delta/delta/compose_test.exs

@@ -298,7 +298,7 @@ defmodule Tests.Delta.Compose do
     end
   end
 
-  describe ".compose/2 (custom embeds)" do
+  describe ".compose/2 (custom delta embed)" do
     @describetag custom_embeds: [TestEmbed]
 
     test "retain an embed with a number" do
@@ -329,6 +329,22 @@ defmodule Tests.Delta.Compose do
       assert Delta.compose(a, b) == expected
     end
 
+    test "retain newline with an embed" do
+      a = [Op.insert("\n")]
+      b = [Op.retain(%{"delta" => [Op.insert("b")]})]
+      expected = [Op.insert(%{"delta" => [Op.insert("b")]})]
+
+      assert Delta.compose(a, b) == expected
+    end
+
+    test "retain string with an embed" do
+      a = [Op.insert("1\n2")]
+      b = [Op.retain(1), Op.retain(%{"delta" => [Op.insert("b")]})]
+      expected = [Op.insert("1"), Op.insert(%{"delta" => [Op.insert("b")]}), Op.insert("2")]
+
+      assert Delta.compose(a, b) == expected
+    end
+
     test "delete a retain" do
       a = [Op.retain(%{"delta" => [Op.insert("a")]})]
       b = [Op.delete(1)]
@@ -337,4 +353,58 @@ defmodule Tests.Delta.Compose do
       assert Delta.compose(a, b) == expected
     end
   end
+
+  describe ".compose/2 (custom map embed)" do
+    @describetag custom_embeds: [MapEmbed]
+
+    test "retain an embed with a number" do
+      a = [Op.insert(%{"map" => "image.png"})]
+      b = [Op.retain(1, %{"bold" => true})]
+      expected = [Op.insert(%{"map" => "image.png"}, %{"bold" => true})]
+
+      assert Delta.compose(a, b) == expected
+    end
+
+    test "retain a number with an embed" do
+      a = [Op.retain(10, %{"bold" => true})]
+      b = [Op.retain(%{"map" => "image.png"})]
+
+      expected = [
+        Op.retain(%{"map" => "image.png"}, %{"bold" => true}),
+        Op.retain(9, %{"bold" => true})
+      ]
+
+      assert Delta.compose(a, b) == expected
+    end
+
+    test "retain an embed with an embed" do
+      a = [Op.retain(%{"map" => "image1.png"})]
+      b = [Op.retain(%{"map" => "image2.png"})]
+
+      assert Delta.compose(a, b) == b
+    end
+
+    test "retain newline with an embed" do
+      a = [Op.insert("\n")]
+      b = [Op.retain(%{"map" => "image.png"})]
+
+      assert Delta.compose(a, b) == [Op.insert(%{"map" => "image.png"})]
+    end
+
+    test "retain string with an embed" do
+      a = [Op.insert("1\n2")]
+      b = [Op.retain(1), Op.retain(%{"map" => "image.png"})]
+      expected = [Op.insert("1"), Op.insert(%{"map" => "image.png"}), Op.insert("2")]
+
+      assert Delta.compose(a, b) == expected
+    end
+
+    test "delete a retain" do
+      a = [Op.retain(%{"map" => "image.png"})]
+      b = [Op.delete(1)]
+      expected = [Op.delete(1)]
+
+      assert Delta.compose(a, b) == expected
+    end
+  end
 end

test/support/case.ex

@@ -5,8 +5,11 @@ defmodule Delta.Support.Case do
   using do
     quote do
       alias Delta
-      alias Delta.{Op, Attr}
-      alias Delta.Support.{TestEmbed, QuoteEmbed}
+      alias Delta.Attr
+      alias Delta.Op
+      alias Delta.Support.MapEmbed
+      alias Delta.Support.QuoteEmbed
+      alias Delta.Support.TestEmbed
     end
   end
 

test/support/map_embed.ex

@@ -0,0 +1,31 @@
+defmodule Delta.Support.MapEmbed do
+  @moduledoc false
+  @behaviour Delta.EmbedHandler
+
+  @impl true
+  def name, do: "map"
+
+  @impl true
+  def compose(_a, b, _keep_nil), do: b
+
+  @impl true
+  def transform(a, b, priority?) do
+    if priority?, do: b, else: a
+  end
+
+  @impl true
+  def invert(_change, base), do: base
+
+  @impl true
+  def diff(base, other) do
+    attr_diff = Delta.Attr.diff(base["attributes"], other["attributes"])
+
+    diff =
+      case {base["insert"], other["insert"]} do
+        {img, img} -> 1
+        {_base, other_img} -> other_img
+      end
+
+    [Delta.Op.retain(diff, attr_diff)]
+  end
+end