[Configuration] Make optional scalar properties nullable

src/Cli/ConfigGenerator.cs

@@ -275,7 +275,11 @@ public static bool TryCreateRuntimeConfig(InitOptions options, FileSystemRuntime
                 DataSource: dataSource,
                 Runtime: new(
                     Rest: new(restEnabled, restPath ?? RestRuntimeOptions.DEFAULT_PATH, options.RestRequestBodyStrict is CliBool.True ? true : false),
-                    GraphQL: new(Enabled: graphQLEnabled, Path: graphQLPath, MultipleMutationOptions: multipleMutationOptions),
+                    GraphQL: new(
+                        Enabled: graphQLEnabled,
+                        Path: graphQLPath,
+                        AllowIntrospection: true,
+                        MultipleMutationOptions: multipleMutationOptions),
                     Mcp: new(
                         Enabled: mcpEnabled,
                         Path: mcpPath ?? McpRuntimeOptions.DEFAULT_PATH,

src/Config/Converters/GraphQLRuntimeOptionsConverterFactory.cs

@@ -45,7 +45,12 @@ internal GraphQLRuntimeOptionsConverter(DeserializationVariableReplacementSettin
 
         public override GraphQLRuntimeOptions? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
-            if (reader.TokenType == JsonTokenType.True || reader.TokenType == JsonTokenType.Null)
+            if (reader.TokenType == JsonTokenType.True)
+            {
+                return new GraphQLRuntimeOptions(Enabled: true);
+            }
+
+            if (reader.TokenType == JsonTokenType.Null)
             {
                 return new GraphQLRuntimeOptions();
             }
@@ -181,9 +186,21 @@ internal GraphQLRuntimeOptionsConverter(DeserializationVariableReplacementSettin
         public override void Write(Utf8JsonWriter writer, GraphQLRuntimeOptions value, JsonSerializerOptions options)
         {
             writer.WriteStartObject();
-            writer.WriteBoolean("enabled", value.Enabled);
-            writer.WriteString("path", value.Path);
-            writer.WriteBoolean("allow-introspection", value.AllowIntrospection);
+
+            if (value.Enabled is not null)
+            {
+                writer.WriteBoolean("enabled", value.Enabled.Value);
+            }
+
+            if (value.Path is not null)
+            {
+                writer.WriteString("path", value.Path);
+            }
+
+            if (value.AllowIntrospection is not null)
+            {
+                writer.WriteBoolean("allow-introspection", value.AllowIntrospection.Value);
+            }
 
             if (value.UserProvidedDepthLimit)
             {

src/Config/Converters/RestRuntimeOptionsConverterFactory.cs

@@ -25,7 +25,12 @@ private class RestRuntimeOptionsConverter : JsonConverter<RestRuntimeOptions>
     {
         public override RestRuntimeOptions? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
-            if (reader.TokenType == JsonTokenType.True || reader.TokenType == JsonTokenType.Null)
+            if (reader.TokenType == JsonTokenType.True)
+            {
+                return new RestRuntimeOptions(Enabled: true);
+            }
+
+            if (reader.TokenType == JsonTokenType.Null)
             {
                 return new RestRuntimeOptions();
             }
@@ -45,9 +50,22 @@ private class RestRuntimeOptionsConverter : JsonConverter<RestRuntimeOptions>
         public override void Write(Utf8JsonWriter writer, RestRuntimeOptions value, JsonSerializerOptions options)
         {
             writer.WriteStartObject();
-            writer.WriteBoolean("enabled", value.Enabled);
-            writer.WriteString("path", value.Path);
-            writer.WriteBoolean("request-body-strict", value.RequestBodyStrict);
+
+            if (value.Enabled is not null)
+            {
+                writer.WriteBoolean("enabled", value.Enabled.Value);
+            }
+
+            if (value.Path is not null)
+            {
+                writer.WriteString("path", value.Path);
+            }
+
+            if (value.RequestBodyStrict is not null)
+            {
+                writer.WriteBoolean("request-body-strict", value.RequestBodyStrict.Value);
+            }
+
             writer.WriteEndObject();
         }
     }

src/Config/ObjectModel/GraphQLRuntimeOptions.cs

@@ -6,9 +6,9 @@
 
 namespace Azure.DataApiBuilder.Config.ObjectModel;
 
-public record GraphQLRuntimeOptions(bool Enabled = true,
-                                    string Path = GraphQLRuntimeOptions.DEFAULT_PATH,
-                                    bool AllowIntrospection = true,
+public record GraphQLRuntimeOptions(bool? Enabled = null,
+                                    string? Path = null,
+                                    bool? AllowIntrospection = null,
                                     int? DepthLimit = null,
                                     MultipleMutationOptions? MultipleMutationOptions = null,
                                     bool EnableAggregation = true,

src/Config/ObjectModel/RestRuntimeOptions.cs

@@ -11,9 +11,9 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 /// for all entities will be exposed.</param>
 /// <param name="RequestBodyStrict">When true, extraneous/unmapped fields in the REST request body are rejected.
 /// When false, extraneous fields are allowed and ignored.
-/// The record default (true) preserves backward compatibility for existing configs that omit this property.
+/// The effective runtime default (true) preserves backward compatibility for existing configs that omit this property.
 /// When dab init generates a new config, request-body-strict is set to false to allow extraneous fields by default.</param>
-public record RestRuntimeOptions(bool Enabled = true, string Path = RestRuntimeOptions.DEFAULT_PATH, bool RequestBodyStrict = true)
+public record RestRuntimeOptions(bool? Enabled = null, string? Path = null, bool? RequestBodyStrict = null)
 {
     public const string DEFAULT_PATH = "/api";
 };

src/Config/ObjectModel/RuntimeConfig.cs

@@ -81,27 +81,22 @@ Runtime is not null &&
     /// </summary>
     [JsonIgnore]
     public bool IsRequestBodyStrict =>
-        Runtime is null ||
-        Runtime.Rest is null ||
-        Runtime.Rest.RequestBodyStrict;
+        Runtime?.Rest?.RequestBodyStrict ?? true;
 
     /// <summary>
     /// Retrieves the value of runtime.graphql.enabled property if present, default is true.
     /// </summary>
     [JsonIgnore]
-    public bool IsGraphQLEnabled => Runtime is null ||
-        Runtime.GraphQL is null ||
-        Runtime.GraphQL.Enabled;
+    public bool IsGraphQLEnabled =>
+        Runtime?.GraphQL?.Enabled ?? true;
 
     /// <summary>
     /// Retrieves the value of runtime.rest.enabled property if present, default is true if its not cosmosdb.
     /// </summary>
     [JsonIgnore]
     public bool IsRestEnabled =>
-        (Runtime is null ||
-         Runtime.Rest is null ||
-         Runtime.Rest.Enabled) &&
-         DataSource?.DatabaseType != DatabaseType.CosmosDB_NoSQL;
+        (Runtime?.Rest?.Enabled ?? true) &&
+        DataSource?.DatabaseType != DatabaseType.CosmosDB_NoSQL;
 
     /// <summary>
     /// Retrieves the value of runtime.mcp.enabled property if present, default is true.
@@ -161,7 +156,7 @@ public string RestPath
             }
             else
             {
-                return Runtime.Rest.Path;
+                return Runtime.Rest.Path ?? RestRuntimeOptions.DEFAULT_PATH;
             }
         }
     }
@@ -180,7 +175,7 @@ public string GraphQLPath
             }
             else
             {
-                return Runtime.GraphQL.Path;
+                return Runtime.GraphQL.Path ?? GraphQLRuntimeOptions.DEFAULT_PATH;
             }
         }
     }
@@ -212,9 +207,7 @@ public bool AllowIntrospection
     {
         get
         {
-            return Runtime is null ||
-                Runtime.GraphQL is null ||
-                Runtime.GraphQL.AllowIntrospection;
+            return Runtime?.GraphQL?.AllowIntrospection ?? true;
         }
     }
 

src/Service.Tests/Configuration/HotReload/ConfigurationHotReloadTests.cs

@@ -913,8 +913,8 @@ public async Task HotReloadValidationFail()
         Assert.IsNotNull(lkgRuntimeConfig);
 
         // Capture properties to verify config hasn't changed
-        bool originalRestEnabled = lkgRuntimeConfig.Runtime.Rest.Enabled;
-        bool originalGraphQLEnabled = lkgRuntimeConfig.Runtime.GraphQL.Enabled;
+        bool originalRestEnabled = lkgRuntimeConfig.IsRestEnabled;
+        bool originalGraphQLEnabled = lkgRuntimeConfig.IsGraphQLEnabled;
         bool originalMcpEnabled = lkgRuntimeConfig.Runtime.Mcp.Enabled;
 
         // Act
@@ -935,9 +935,9 @@ await WaitForConditionAsync(
 
         // Assert - Verify the configuration hasn't changed by comparing properties
         Assert.IsNotNull(newRuntimeConfig, "RuntimeConfig should not be null after failed hot-reload.");
-        Assert.AreEqual(originalRestEnabled, newRuntimeConfig.Runtime.Rest.Enabled,
+        Assert.AreEqual(originalRestEnabled, newRuntimeConfig.IsRestEnabled,
             "REST enabled setting should remain unchanged after hot-reload failure.");
-        Assert.AreEqual(originalGraphQLEnabled, newRuntimeConfig.Runtime.GraphQL.Enabled,
+        Assert.AreEqual(originalGraphQLEnabled, newRuntimeConfig.IsGraphQLEnabled,
             "GraphQL enabled setting should remain unchanged after hot-reload failure.");
         Assert.AreEqual(originalMcpEnabled, newRuntimeConfig.Runtime.Mcp.Enabled,
             "MCP enabled setting should remain unchanged after hot-reload failure.");
@@ -963,8 +963,8 @@ public async Task HotReloadParsingFail()
         Assert.IsNotNull(lkgRuntimeConfig);
 
         // Capture properties to verify config hasn't changed
-        bool originalRestEnabled = lkgRuntimeConfig.Runtime.Rest.Enabled;
-        bool originalGraphQLEnabled = lkgRuntimeConfig.Runtime.GraphQL.Enabled;
+        bool originalRestEnabled = lkgRuntimeConfig.IsRestEnabled;
+        bool originalGraphQLEnabled = lkgRuntimeConfig.IsGraphQLEnabled;
 
         // Act
         GenerateConfigFile(
@@ -982,9 +982,9 @@ await WaitForConditionAsync(
 
         // Assert - Verify the configuration hasn't changed by comparing properties
         Assert.IsNotNull(newRuntimeConfig, "RuntimeConfig should not be null after failed hot-reload.");
-        Assert.AreEqual(originalRestEnabled, newRuntimeConfig.Runtime.Rest.Enabled,
+        Assert.AreEqual(originalRestEnabled, newRuntimeConfig.IsRestEnabled,
             "REST enabled setting should remain unchanged after hot-reload failure.");
-        Assert.AreEqual(originalGraphQLEnabled, newRuntimeConfig.Runtime.GraphQL.Enabled,
+        Assert.AreEqual(originalGraphQLEnabled, newRuntimeConfig.IsGraphQLEnabled,
             "GraphQL enabled setting should remain unchanged after hot-reload failure.");
     }
 

src/Service.Tests/UnitTests/RuntimeConfigLoaderJsonDeserializerTests.cs

@@ -408,6 +408,108 @@ public void TestNullableOptionalProps()
             TryParseAndAssertOnDefaults("{" + emptyTelemetrySubProps, out _);
         }
 
+        /// <summary>
+        /// Verifies that optional scalar runtime properties which are omitted from
+        /// the input configuration remain omitted after serialization, while their
+        /// effective runtime behavior still uses the documented defaults.
+        /// </summary>
+        [TestMethod]
+        public void TestOptionalScalarPropsRemainOmittedAfterSerialization()
+        {
+            string json = @"{
+                ""data-source"": {
+                    ""database-type"": ""mssql"",
+                    ""connection-string"": ""@env('test-connection-string')""
+                },
+                ""runtime"": {
+                    ""rest"": { },
+                    ""graphql"": { }
+                },
+                ""entities"": { }
+            }";
+
+            Assert.IsTrue(RuntimeConfigLoader.TryParseConfig(json, out RuntimeConfig runtimeConfig));
+
+            string serialized = runtimeConfig.ToJson();
+            using JsonDocument document = JsonDocument.Parse(serialized);
+
+            JsonElement runtime = document.RootElement.GetProperty("runtime");
+
+            JsonElement rest = runtime.GetProperty("rest");
+            Assert.IsFalse(rest.TryGetProperty("enabled", out _));
+            Assert.IsFalse(rest.TryGetProperty("path", out _));
+            Assert.IsFalse(rest.TryGetProperty("request-body-strict", out _));
+
+            JsonElement graphql = runtime.GetProperty("graphql");
+            Assert.IsFalse(graphql.TryGetProperty("enabled", out _));
+            Assert.IsFalse(graphql.TryGetProperty("path", out _));
+            Assert.IsFalse(graphql.TryGetProperty("allow-introspection", out _));
+
+            Assert.IsTrue(runtimeConfig.IsRestEnabled);
+            Assert.AreEqual(RestRuntimeOptions.DEFAULT_PATH, runtimeConfig.RestPath);
+            Assert.IsTrue(runtimeConfig.IsRequestBodyStrict);
+
+            Assert.IsTrue(runtimeConfig.IsGraphQLEnabled);
+            Assert.AreEqual(GraphQLRuntimeOptions.DEFAULT_PATH, runtimeConfig.GraphQLPath);
+            Assert.IsTrue(runtimeConfig.AllowIntrospection);
+        }
+
+        /// <summary>
+        /// Verifies that omitted optional scalar properties do not materialize
+        /// defaults during serialization and overwrite values from a base config.
+        /// </summary>
+        [TestMethod]
+        public void TestOptionalScalarPropsDoNotOverrideBaseValuesAfterSerialization()
+        {
+            string baseJson = @"{
+                ""runtime"": {
+                    ""rest"": {
+                        ""enabled"": false,
+                        ""path"": ""/base-rest"",
+                        ""request-body-strict"": false
+                    },
+                    ""graphql"": {
+                        ""enabled"": false,
+                        ""path"": ""/base-graphql"",
+                        ""allow-introspection"": false
+                    }
+                }
+            }";
+
+            string overrideJson = @"{
+                ""data-source"": {
+                    ""database-type"": ""mssql"",
+                    ""connection-string"": ""@env('test-connection-string')""
+                },
+                ""runtime"": {
+                    ""rest"": { },
+                    ""graphql"": { }
+                },
+                ""entities"": { }
+            }";
+
+            Assert.IsTrue(
+                RuntimeConfigLoader.TryParseConfig(
+                    overrideJson,
+                    out RuntimeConfig overrideConfig));
+
+            string serializedOverride = overrideConfig.ToJson();
+            string mergedJson = MergeJsonProvider.Merge(baseJson, serializedOverride);
+
+            using JsonDocument document = JsonDocument.Parse(mergedJson);
+            JsonElement runtime = document.RootElement.GetProperty("runtime");
+
+            JsonElement rest = runtime.GetProperty("rest");
+            Assert.IsFalse(rest.GetProperty("enabled").GetBoolean());
+            Assert.AreEqual("/base-rest", rest.GetProperty("path").GetString());
+            Assert.IsFalse(rest.GetProperty("request-body-strict").GetBoolean());
+
+            JsonElement graphql = runtime.GetProperty("graphql");
+            Assert.IsFalse(graphql.GetProperty("enabled").GetBoolean());
+            Assert.AreEqual("/base-graphql", graphql.GetProperty("path").GetString());
+            Assert.IsFalse(graphql.GetProperty("allow-introspection").GetBoolean());
+        }
+
         #endregion Positive Tests
 
         #region Negative Tests