Made type aliases a thing

While working on the automatic protocol generators, it became clear
that type aliases needed to be their own thing, as they operate quite
differently from the other defined things in the jsonrpc
protocol. Since they're just aliases, it makes sense to keep their
definitions on hand and then spit them out when other things make use
of them during encode and decode.

This did require going back to encoding and ensuring all the encode
functions return OK tuples.

apps/language_server/.formatter.exs

@@ -4,6 +4,7 @@ impossible_to_format = [
 ]
 
 proto_dsl = [
+  defalias: 1,
   defenum: 1,
   defnotification: 2,
   defnotification: 3,

apps/language_server/lib/language_server/experimental/protocol/proto.ex

@@ -7,6 +7,7 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto do
       alias ElixirLS.LanguageServer.Experimental.Protocol.Proto.LspTypes
 
       import ElixirLS.LanguageServer.Experimental.Protocol.Proto.TypeFunctions
+      import Proto.Alias, only: [defalias: 1]
       import Proto.Enum, only: [defenum: 1]
       import Proto.Notification, only: [defnotification: 2, defnotification: 3]
       import Proto.Request, only: [defrequest: 3]

apps/language_server/lib/language_server/experimental/protocol/proto/alias.ex

@@ -0,0 +1,22 @@
+defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Alias do
+  alias ElixirLS.LanguageServer.Experimental.Protocol.Proto.CompileMetadata
+
+  defmacro defalias(alias_definition) do
+    caller_module = __CALLER__.module
+    CompileMetadata.add_type_alias_module(caller_module)
+
+    quote location: :keep do
+      def definition do
+        unquote(alias_definition)
+      end
+
+      def __meta__(:type) do
+        :type_alias
+      end
+
+      def __meta__(:param_names) do
+        []
+      end
+    end
+  end
+end

apps/language_server/lib/language_server/experimental/protocol/proto/compile_metadata.ex

@@ -5,6 +5,7 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.CompileMetadata do
 
   @notification_modules_key {__MODULE__, :notification_modules}
   @type_modules_key {__MODULE__, :type_modules}
+  @type_alias_modules_key {__MODULE__, :type_alias_modules}
   @request_modules_key {__MODULE__, :request_modules}
   @response_modules_key {__MODULE__, :response_modules}
 
@@ -20,6 +21,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.CompileMetadata do
     :persistent_term.get(@response_modules_key, [])
   end
 
+  def type_alias_modules do
+    :persistent_term.get(@type_alias_modules_key)
+  end
+
   def type_modules do
     :persistent_term.get(@type_modules_key)
   end
@@ -40,6 +45,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.CompileMetadata do
     add_module(@type_modules_key, module)
   end
 
+  def add_type_alias_module(module) do
+    add_module(@type_alias_modules_key, module)
+  end
+
   defp update(key, initial_value, update_fn) do
     case :persistent_term.get(key, :not_found) do
       :not_found -> :persistent_term.put(key, initial_value)

apps/language_server/lib/language_server/experimental/protocol/proto/enum.ex

@@ -22,7 +22,7 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Enum do
       for {name, value} <- opts do
         quote location: :keep do
           def encode(unquote(name)) do
-            unquote(value)
+            {:ok, unquote(value)}
           end
         end
       end
@@ -36,6 +36,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Enum do
 
       unquote_splicing(encoders)
 
+      def encode(val) do
+        {:error, {:invalid_value, __MODULE__, val}}
+      end
+
       unquote_splicing(enum_macros)
 
       def __meta__(:types) do

apps/language_server/lib/language_server/experimental/protocol/proto/field.ex

@@ -51,6 +51,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Field do
     {:ok, orig_value}
   end
 
+  def extract(:float, _name, orig_value) when is_float(orig_value) do
+    {:ok, orig_value}
+  end
+
   def extract(:string, _name, orig_value) when is_binary(orig_value) do
     {:ok, orig_value}
   end
@@ -59,8 +63,12 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Field do
     {:ok, orig_value}
   end
 
+  def extract({:type_alias, alias_module}, name, orig_value) do
+    extract(alias_module.definition(), name, orig_value)
+  end
+
   def extract(module, _name, orig_value)
-      when is_atom(module) and module not in [:integer, :string, :boolean] do
+      when is_atom(module) and module not in [:integer, :string, :boolean, :float] do
     module.parse(orig_value)
   end
 
@@ -103,15 +111,15 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Field do
   end
 
   def encode(:any, field_value) do
-    field_value
+    {:ok, field_value}
   end
 
   def encode({:literal, value}, _) do
-    value
+    {:ok, value}
   end
 
   def encode({:optional, _}, nil) do
-    :"$__drop__"
+    {:ok, :"$__drop__"}
   end
 
   def encode({:optional, field_type}, field_value) do
@@ -128,44 +136,99 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Field do
   end
 
   def encode({:list, list_type}, field_value) when is_list(field_value) do
-    Enum.map(field_value, &encode(list_type, &1))
+    encoded =
+      Enum.reduce_while(field_value, [], fn element, acc ->
+        case encode(list_type, element) do
+          {:ok, encoded} -> {:cont, [encoded | acc]}
+          error -> {:halt, error}
+        end
+      end)
+
+    case encoded do
+      encoded_list when is_list(encoded_list) ->
+        {:ok, Enum.reverse(encoded_list)}
+
+      error ->
+        error
+    end
   end
 
-  def encode(:integer, field_value) do
-    field_value
+  def encode(:integer, field_value) when is_integer(field_value) do
+    {:ok, field_value}
+  end
+
+  def encode(:integer, string_value) when is_binary(string_value) do
+    case Integer.parse(string_value) do
+      {int_value, ""} -> {:ok, int_value}
+      _ -> {:error, {:invalid_integer, string_value}}
+    end
+  end
+
+  def encode(:float, float_value) when is_float(float_value) do
+    {:ok, float_value}
   end
 
   def encode(:string, field_value) when is_binary(field_value) do
-    field_value
+    {:ok, field_value}
   end
 
   def encode(:boolean, field_value) when is_boolean(field_value) do
-    field_value
+    {:ok, field_value}
   end
 
   def encode({:map, value_type, _}, field_value) when is_map(field_value) do
-    Map.new(field_value, fn {k, v} -> {k, encode(value_type, v)} end)
+    map_fields =
+      Enum.reduce_while(field_value, [], fn {key, value}, acc ->
+        case encode(value_type, value) do
+          {:ok, encoded_value} -> {:cont, [{key, encoded_value} | acc]}
+          error -> {:halt, error}
+        end
+      end)
+
+    case map_fields do
+      fields when is_list(fields) -> {:ok, Map.new(fields)}
+      error -> error
+    end
   end
 
   def encode({:params, param_defs}, field_value) when is_map(field_value) do
-    Map.new(param_defs, fn {param_name, param_type} ->
-      {param_name, encode(param_type, Map.get(field_value, param_name))}
-    end)
+    param_fields =
+      Enum.reduce_while(param_defs, [], fn {param_name, param_type}, acc ->
+        unencoded = Map.get(field_value, param_name)
+
+        case encode(param_type, unencoded) do
+          {:ok, encoded_value} -> {:cont, [{param_name, encoded_value} | acc]}
+          error -> {:halt, error}
+        end
+      end)
+
+    case param_fields do
+      fields when is_list(fields) -> {:ok, Map.new(fields)}
+      error -> error
+    end
   end
 
   def encode({:constant, constant_module}, field_value) do
-    constant_module.encode(field_value)
+    {:ok, constant_module.encode(field_value)}
+  end
+
+  def encode({:type_alias, alias_module}, field_value) do
+    encode(alias_module.definition(), field_value)
   end
 
   def encode(module, field_value) when is_atom(module) do
     if function_exported?(module, :encode, 1) do
       module.encode(field_value)
     else
-      field_value
+      {:ok, field_value}
     end
   end
 
   def encode(_, nil) do
     nil
   end
+
+  def encode(type, value) do
+    {:error, {:invalid_type, type, value}}
+  end
 end

apps/language_server/lib/language_server/experimental/protocol/proto/macros/json.ex

@@ -8,7 +8,7 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.Macros.Json do
           encoded_pairs =
             for {field_name, field_type} <- unquote(dest_module).__meta__(:types),
                 field_value = get_field_value(value, field_name),
-                encoded_value = Field.encode(field_type, field_value),
+                {:ok, encoded_value} = Field.encode(field_type, field_value),
                 encoded_value != :"$__drop__" do
               {field_name, encoded_value}
             end

apps/language_server/lib/language_server/experimental/protocol/proto/type_functions.ex

@@ -3,6 +3,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.TypeFunctions do
     :integer
   end
 
+  def float do
+    :float
+  end
+
   def string do
     :string
   end
@@ -15,6 +19,10 @@ defmodule ElixirLS.LanguageServer.Experimental.Protocol.Proto.TypeFunctions do
     :string
   end
 
+  def type_alias(alias_module) do
+    {:type_alias, alias_module}
+  end
+
   def literal(what) do
     {:literal, what}
   end

apps/language_server/test/experimental/protocol/proto_test.exs

@@ -50,6 +50,23 @@ defmodule ElixirLS.LanguageServer.Experimental.ProtoTest do
     end
   end
 
+  describe "float fields" do
+    defmodule FloatField do
+      use Proto
+      deftype float_field: float()
+    end
+
+    test "can parse a float field" do
+      assert {:ok, val} = FloatField.parse(%{"floatField" => 494.02})
+      assert val.float_field == 494.02
+    end
+
+    test "rejects nil float fields" do
+      assert {:error, {:invalid_value, :float_field, "string"}} =
+               FloatField.parse(%{"floatField" => "string"})
+    end
+  end
+
   describe "list fields" do
     defmodule ListField do
       use Proto
@@ -99,6 +116,42 @@ defmodule ElixirLS.LanguageServer.Experimental.ProtoTest do
     end
   end
 
+  describe "type aliases" do
+    defmodule TypeAlias do
+      use Proto
+      defalias one_of([string(), list_of(string())])
+    end
+
+    defmodule UsesAlias do
+      use Proto
+
+      deftype alias: type_alias(TypeAlias), name: string()
+    end
+
+    test "parses a single item correctly" do
+      assert {:ok, uses} = UsesAlias.parse(%{"name" => "uses", "alias" => "foo"})
+      assert uses.name == "uses"
+      assert uses.alias == "foo"
+    end
+
+    test "parses a list correctly" do
+      assert {:ok, uses} = UsesAlias.parse(%{"name" => "uses", "alias" => ["foo", "bar"]})
+      assert uses.name == "uses"
+      assert uses.alias == ~w(foo bar)
+    end
+
+    test "encodes correctly" do
+      assert {:ok, encoded} = encode_and_decode(UsesAlias.new(alias: "hi", name: "easy"))
+      assert encoded["alias"] == "hi"
+      assert encoded["name"] == "easy"
+    end
+
+    test "parse fails if the type isn't correct" do
+      assert {:error, {:incorrect_type, _, %{}}} =
+               UsesAlias.parse(%{"name" => "ua", "alias" => %{}})
+    end
+  end
+
   describe "optional fields" do
     defmodule OptionalString do
       use Proto