test(api): enforce nullable channel now playing schema

ErsatzTV.Tests/Controllers/OpenApiErrorResponseContractTests.cs

@@ -71,7 +71,32 @@ public class OpenApiErrorResponseContractTests
         stateProperties.TryGetProperty("channelId", out _).ShouldBeTrue();
         stateProperties.TryGetProperty("channelNumber", out _).ShouldBeTrue();
         stateProperties.TryGetProperty("onAir", out _).ShouldBeTrue();
-        stateProperties.TryGetProperty("nowPlaying", out _).ShouldBeTrue();
+        stateProperties.TryGetProperty("nowPlaying", out JsonElement nowPlaying).ShouldBeTrue();
+
+        JsonElement nowPlayingOneOf = nowPlaying.GetProperty("oneOf");
+        nowPlayingOneOf.EnumerateArray().Count().ShouldBe(2);
+        nowPlayingOneOf.EnumerateArray()
+            .Any(s => s.TryGetProperty("type", out JsonElement type) && type.GetString() == "null")
+            .ShouldBeTrue();
+        nowPlayingOneOf.EnumerateArray()
+            .Any(s => s.TryGetProperty("$ref", out JsonElement schemaRef) &&
+                schemaRef.GetString() == "#/components/schemas/ChannelNowPlayingResponseModel")
+            .ShouldBeTrue();
+
+        JsonElement nowPlayingProperties = document.RootElement
+            .GetProperty("components")
+            .GetProperty("schemas")
+            .GetProperty("ChannelNowPlayingResponseModel")
+            .GetProperty("properties");
+
+        nowPlayingProperties.TryGetProperty("title", out _).ShouldBeTrue();
+        nowPlayingProperties.TryGetProperty("startUtc", out JsonElement startUtc).ShouldBeTrue();
+        nowPlayingProperties.TryGetProperty("finishUtc", out JsonElement finishUtc).ShouldBeTrue();
+
+        startUtc.GetProperty("type").GetString().ShouldBe("string");
+        startUtc.GetProperty("format").GetString().ShouldBe("date-time");
+        finishUtc.GetProperty("type").GetString().ShouldBe("string");
+        finishUtc.GetProperty("format").GetString().ShouldBe("date-time");
     }
 
     [TestCase("/api/channels/{id}", "get", "404")]

ErsatzTV/wwwroot/openapi/v1.json

@@ -3568,7 +3568,14 @@
             "type": "boolean"
           },
           "nowPlaying": {
-            "$ref": "#/components/schemas/ChannelNowPlayingResponseModel"
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/ChannelNowPlayingResponseModel"
+              }
+            ]
           }
         }
       },