[csharp-netcore] conditionalSerialization doesn't serialize required fields set in constructor and always serializes bools

[panayot-cankov]

I have a model with some optional (not-required) fields. The csharp-netcore will generate code that mostly serializes nullable and bool properties even when not explicitly set.

The optionalEmitDefaultValues would set EmitDefaultValues to true and output properties even more aggressively.

The conditionalSerialization would make some things better but:

• The parameterized constructor will still always mark the _flag* for bool fields due to the generated if (null != bool) _flag* = true check that is always true and always marks primitive types
• The parameterized constructor will not mark the required properties _flag*

There is something off in the way optional nullable and primitive types are handled.

For optional properties, I expected if the properties are not set on the model object explicitly, that the properties will not be serialized and sent in the JSON payload.

Then in case optional properties are set on the object, even if using a default value, that they still would be serialized and sent in the JSON payload.

Issue 1: Required fields are never marked in the constructor when using conditionalSerialization

Here is what conditionalSerialization generates for the required string "Type" property:

            // to ensure "type" is required (not null)
            if (type == null)
            {
                throw new ArgumentNullException("type is a required property for ComponentUsed and cannot be null");
            }
            this._Type = type;

It misses something like:

            this._Type = type;
            if (this.Type != null)
            {
                this._flagType = true;
            }

And then it would be good.

I think the code from this: https://github.com/OpenAPITools/openapi-generator/blob/032e1a42d66517cfc2d384826164ced097ac2e6b/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache#L189-L192

Should be copied here: https://github.com/OpenAPITools/openapi-generator/blob/032e1a42d66517cfc2d384826164ced097ac2e6b/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache#L151-L163

Since the constructor is not setting the _flagType, the Type is then not serialized.

Currently the "Type" is not sent unless:

• Passed to the constructor to avoid the null check
• Also set as property to mark the _flagType to true

Issue 2: Optional primitive type fields are always marked in the constructor when using conditionalSerialization

Here: https://github.com/OpenAPITools/openapi-generator/blob/032e1a42d66517cfc2d384826164ced097ac2e6b/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache#L189-L192

If the model has optional (but non-nullable) primitive type like bool, the generator would generate:

            this._IsTrial = isTrial;
            if (this.IsTrial != null)
            {
                this._flagIsTrial = true;
            }

The IDE would show a bunch of warnings:

Severity	Code	Description	Project	File	Line	Suppression State
Warning	CS0472	The result of the expression is always 'true' since a value of type 'bool' is never equal to 'null' of type 'bool?'

And since the expression is always true, the _flagIsTrial is always marked and then serialized.

I don't know how to remedy this unless I make all primitive types also nullable and pass nullable around.

I also don't know how to fix that. Ideally the bool should become bool? in the constructor and if it is provided as null it should be treated as "not provided", otherwise if it has value - set the value to the field and raise the _flag*. But then I am not sure how nullable model types would be affected.

Feature Request

The way my models are, they are becoming a bit complex with some multiple inheritance, I have some code that can assign the properties from smaller types to larger types. Ideally If I could switch off constructor based null checking and have just an empty constructor for the model classes, then use always properties to assign values so they work with the conditionalSerialization. And if any validation is still necessary - have an explicit method to perform the validation after the properties are populated, perhaps like using validatable and the generated validation code, it would be perfect.

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I may also be missing something, I'd be happy on some suggestions.