fix empty set as a single object property decoding (#147)

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - crash after updating `db_connection` to `2.5`.
+- decoding a single propery for `EdgeDB.Object` that equals to an empty set.
 - not catching an `EdgeDB.Error` exception during parameters encoding,
  which caused throwing an exception for non-`!` functions.
 

lib/edgedb/protocol/codecs/object.ex

@@ -295,9 +295,20 @@ defimpl EdgeDB.Protocol.Codec, for: EdgeDB.Protocol.Codecs.Object do
  element.name
  end
 
+ single_property? =
+ element.cardinality in [:at_most_one, :one] and
+ (link_property?(element) or not link?(element))
+
+ value =
+ if single_property? do
+ nil
+ else
+ @empty_set
+ end
+
  field = %EdgeDB.Object.Field{
  name: name,
- value: @empty_set,
+ value: value,
  is_link: link?(element),
  is_link_property: link_property?(element),
  is_implicit: implicit?(element)

test/edgedb/protocol/codecs/object_test.exs

@@ -232,17 +232,27 @@ defmodule Tests.EdgeDB.Protocol.Codecs.ObjectTest do
  end)
  end
 
- test "decoding object with property equals to empty set", %{client: client} do
- rollback(client, fn client ->
- object =
- EdgeDB.query_required_single!(client, """
- select {
- a := <str>{}
- }
- limit 1
- """)
+ test "decoding object with a single property equals to empty set", %{client: client} do
+ object =
+ EdgeDB.query_required_single!(client, """
+ select {
+ a := <str>{}
+ }
+ limit 1
+ """)
 
- assert Enum.empty?(object[:a])
- end)
+ assert is_nil(object[:a])
+ end
+
+ test "decoding object with a multi property equals to empty set", %{client: client} do
+ object =
+ EdgeDB.query_required_single!(client, """
+ select {
+ multi a := <str>{}
+ }
+ limit 1
+ """)
+
+ assert Enum.empty?(object[:a])
  end
 end