Allow casting atoms as strings (open-api-spex#497)

Author: zorbash

lib/open_api_spex/cast.ex

@@ -65,14 +65,14 @@ defmodule OpenApiSpex.Cast do
       iex> schema = %Schema{type: :string}
       iex> Cast.cast(schema, "a string")
       {:ok, "a string"}
-      iex> Cast.cast(schema, :not_a_string)
+      iex> Cast.cast(schema, 1..100)
       {
         :error,
         [
           %OpenApiSpex.Cast.Error{
             reason: :invalid_type,
             type: :string,
-            value: :not_a_string
+            value: 1..100
           }
         ]
       }

lib/open_api_spex/cast/string.ex

@@ -106,6 +106,13 @@ defmodule OpenApiSpex.Cast.String do
     {:ok, value}
   end
 
+  def cast(%{value: value} = ctx) when is_atom(value) and value not in [true, false, nil] do
+    case cast(%{ctx | value: to_string(value)}) do
+      {:ok, _value} -> {:ok, value}
+      error -> error
+    end
+  end
+
   def cast(%{value: value} = ctx) when is_binary(value) do
     apply_validation(ctx, @schema_fields)
   end

test/cast/string_test.exs

@@ -15,6 +15,12 @@ defmodule OpenApiSpex.CastStringTest do
       assert error.value == %{}
     end
 
+    test "preserves atom values" do
+      schema = %Schema{type: :string}
+
+      assert cast(value: :hello, schema: schema) == {:ok, :hello}
+    end
+
     test "string with pattern" do
       schema = %Schema{type: :string, pattern: ~r/\d-\d/}
       assert cast(value: "1-2", schema: schema) == {:ok, "1-2"}
@@ -80,6 +86,7 @@ defmodule OpenApiSpex.CastStringTest do
     # Note: we measure length of string after trimming leading and trailing whitespace
     test "minLength" do
       schema = %Schema{type: :string, minLength: 1}
+
       assert {:ok, "a"} = cast(value: "a", schema: schema)
       assert {:error, [error]} = cast(value: "", schema: schema)
       assert %Error{} = error
@@ -89,27 +96,32 @@ defmodule OpenApiSpex.CastStringTest do
     # Note: we measure length of string after trimming leading and trailing whitespace
     test "maxLength" do
       schema = %Schema{type: :string, maxLength: 1}
+
       assert {:ok, "a"} = cast(value: "a", schema: schema)
-      assert {:error, [error]} = cast(value: "aa", schema: schema)
-      assert %Error{} = error
-      assert error.reason == :max_length
+      assert {:error, [%Error{reason: :max_length}]} = cast(value: "aa", schema: schema)
+
+      assert {:ok, :a} = cast(value: :a, schema: schema)
+      assert {:error, [%Error{reason: :max_length}]} = cast(value: :aa, schema: schema)
     end
 
     test "maxLength and minLength" do
       schema = %Schema{type: :string, minLength: 1, maxLength: 2}
-      assert {:error, [error]} = cast(value: "", schema: schema)
-      assert %Error{} = error
-      assert error.reason == :min_length
-      assert {:error, [error]} = cast(value: "aaa", schema: schema)
-      assert %Error{} = error
-      assert error.reason == :max_length
+
+      assert {:error, [%Error{reason: :min_length}]} = cast(value: "", schema: schema)
+      assert {:error, [%Error{reason: :max_length}]} = cast(value: "aaa", schema: schema)
+
+      assert {:error, [%Error{reason: :min_length}]} = cast(value: :"", schema: schema)
+      assert {:error, [%Error{reason: :max_length}]} = cast(value: :aaa, schema: schema)
     end
 
     test "minLength and pattern" do
       schema = %Schema{type: :string, minLength: 1, pattern: ~r/\d-\d/}
-      assert {:error, errors} = cast(value: "", schema: schema)
-      assert length(errors) == 2
-      assert Enum.map(errors, & &1.reason) == [:invalid_format, :min_length]
+
+      assert {:error, [%Error{reason: :invalid_format}, %Error{reason: :min_length}]} =
+               cast(value: "", schema: schema)
+
+      assert {:error, [%Error{reason: :invalid_format}, %Error{reason: :min_length}]} =
+               cast(value: :"", schema: schema)
     end
   end
 end

test/test_assertions_test.exs

@@ -13,7 +13,7 @@ defmodule OpenApiSpex.TestAssertionsTest do
 
     test "failure" do
       schema = %Schema{type: :string}
-      cast_context = %Cast{value: :nope, schema: schema}
+      cast_context = %Cast{value: 1.100, schema: schema}
 
       try do
         TestAssertions.assert_schema(cast_context)