Getting empty enum with allOf of oneOfs

Getting empty enum with allOfs of oneOfs

For this schema:

{
  "openapi": "3.0.0",
  "info": {
    "title": "NEAR Protocol JSON RPC API",
    "version": "1.1.2"
  },
  "paths": {},
  "components": {
    "schemas": {
      "MyStruct": {
        "allOf": [
          {
            "oneOf": [
              {
                "properties": {
                  "myfirsttag": {
                    "enum": [
                      "a"
                    ],
                    "type": "string"
                  }
                },
                "required": [
                  "myfirsttag"
                ],
                "type": "object"
              },
              {
                "format": "uint64",
                "minimum": 0,
                "properties": {
                  "myfirsttag": {
                    "enum": [
                      "b"
                    ],
                    "type": "string"
                  }
                },
                "required": [
                  "myfirsttag"
                ],
                "type": "object"
              }
            ]
          },
          {
            "oneOf": [
              {
                "properties": {
                  "mysecondtag": {
                    "enum": [
                      "c"
                    ],
                    "type": "string"
                  }
                },
                "required": [
                  "mysecondtag"
                ],
                "type": "object"
              },
              {
                "format": "uint64",
                "minimum": 0,
                "properties": {
                  "mysecondtag": {
                    "enum": [
                      "d"
                    ],
                    "type": "string"
                  }
                },
                "required": [
                  "mysecondtag"
                ],
                "type": "object"
              }
            ]
          }
        ],
        "title": "MyStruct",
        "type": "object"
      }
    }
  }
}

The output is:

    #[derive(:: serde :: Deserialize, :: serde :: Serialize, Clone, Debug)]
    #[serde(untagged)]
    pub enum MyStruct {
        Variant0(MyStructVariant0),
        Variant1(MyStructVariant1),
    }

    #[derive(:: serde :: Deserialize, :: serde :: Serialize, Clone, Debug)]
    #[serde(untagged)]
    pub enum MyStructVariant0 {
        Variant0(MyStructVariant0Variant0),
        Variant1(MyStructVariant0Variant1),
    }

    #[serde(deny_unknown_fields)]
    pub enum MyStructVariant0Variant0 {}

There was a similar issue https://github.com/oxidecomputer/typify/issues/829 which was successfully fixed. This thing is a more advanced.

@ahl here you mention the ongoing work "to separate out schema processing such as merging schemas". Is that going to help?

Use serde(flatten) whenever possible

I would create a second issue out of that for the following. But let it be here for now. I put it here as it may be connected
The previous schema is actually created from the rust code with schemars:

#[derive(JsonSchema)]
struct MyStruct {
    #[serde(flatten)]
    pub first_enum: MyFirstEnum,
    #[serde(flatten)]
    pub second_enum: MySecondEnum,
}

#[derive(JsonSchema)]
#[serde(tag = "myfirsttag", rename_all = "snake_case")]
enum MyFirstEnum {
    A(String),
    B(u64)
}

#[derive(JsonSchema)]
#[serde(tag = "mysecondtag", rename_all = "snake_case")]
enum MySecondEnum {
    C(String),
    D(u64)
}

So after that, I would say "let's use serde(flatten) whenever it's possible". For this case, it sounds reasonable. Firstly, it deduplicates the code. Secondly, it helps with naming. Though I am not sure if it's reasonable for the general case.

Start by tracing the schema-processing and schema-merging work referenced in issue 856, and compare the related fix in issue 829 against the provided MyStruct schema and generated Rust output. Done means this allOf/oneOf combination no longer produces an empty enum, with serde(flatten) used where the resulting representation permits it.