"anyOf" with "required" doesn't appear to be generating the right enum variants

Start by reproducing the v0.1.0 behavior with the ResourceDescriptor schema and example JSON, focusing on how anyOf and required are converted into the generated Rust enum. Compare the generated variants with validation behavior from other validators. Done means objects containing any one or more of content, digest, or uri are accepted while objects containing none are rejected.

I am running against v0.1.0.

I have a type definition in the json schema called ResourceDescriptor. It should require at least one of content, digest, uri fields to be set. However, what I'm seeing is that it makes them exclusive with each other.

Here's my json schema:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "SummarySCAI",
  "type": "object",
  "properties": {
    "_type": {
      "type": "string"
    },
    "subject": {
      "type": "array",
      "items": {
        "$ref": "#/$defs/ResourceDescriptor"
      }
    },
    "predicateType": {
      "type": "string"
    },
    "predicate": {
      "type": "object",
      "properties": {
        "attributes": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "attribute": {
                "type": "string",
                "enum": [
                  "PASSED_DEVELOPMENT_ENVIRONMENT",
                  "PASSED_SOURCE",
                  "PASSED_BUILD",
                  "PASSED_PACKAGE",
                  "PASSED_DEPLOY"
                ]
              },
              "conditions": {
                "type": "object",
                "properties": {
                  "policy": {
                    "type": "string"
                  }
                }
              },
              "evidence": {
                "$ref": "#/$defs/ResourceDescriptor"
              }
            },
            "required": ["attribute", "evidence"]
          }
        },
        "producer": {
          "$ref": "#/$defs/ResourceDescriptor"
        }
      },
      "required": ["attributes", "producer"]
    }
  },
  "required": ["_type", "subject", "predicateType", "predicate"],
  "$defs": {
    "ResourceDescriptor": {
      "type": "object",
      "properties": {
        "name": {
          "type": "string"
        },
        "uri": {
          "type": "string"
        },
        "digest": {
          "type": "object",
          "properties": {
            "sha256": {
              "type": "string"
            }
          },
          "required": ["sha256"]
        },
        "content": {
          "type": "string"
        },
        "downloadLocation": {
          "type": "string"
        },
        "mediaType": {
          "type": "string"
        },
        "annotations": {
          "type": "object",
          "additionalProperties": true
        }
      },
      "anyOf": [
        {
          "required": ["uri"]
        },
        {
          "required": ["digest"]
        },
        {
          "required": ["content"]
        }
      ],
      "additionalProperties": false
    }
  }
}

It generates an enum like:

pub enum ResourceDescriptor {
    Variant0 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
        uri: String,
    },
    Variant1 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        digest: ResourceDescriptorVariant1Digest,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
    },
    Variant2 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        content: String,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
    },
}

I would expect the enum variants to look more like:

pub enum ResourceDescriptor {
    Variant0 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        content: Option<String>,
        digest: Option<ResourceDescriptorVariant1Digest>,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
        uri: String,
    },
    Variant1 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        content: Option<String>,
        digest: ResourceDescriptorVariant1Digest,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
        uri: Option<String>,
    },
    Variant2 {
        #[serde(default, skip_serializing_if = "serde_json::Map::is_empty")]
        annotations: serde_json::Map<String, serde_json::Value>,
        content: String,
        digest: Option<ResourceDescriptorVariant1Digest>,
        #[serde(
            rename = "downloadLocation",
            default,
            skip_serializing_if = "Option::is_none"
        )]
        download_location: Option<String>,
        #[serde(rename = "mediaType", default, skip_serializing_if = "Option::is_none")]
        media_type: Option<String>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
        uri: Option<String>,
    },
}

If I run this schema against other validators it does work as intended where as long I have one of content, digest, or uri set it validates.

Here is an example json that does not validate with an error: Error: data did not match any variant of untagged enum ResourceDescriptor at line 20 column 7

{
  "_type": "https://in-toto.io/Statement/v1",
  "subject": [
    {
      "name": "example-software-artifact",
      "digest": { "sha256": "a1b2c3d4e5f6..." }
    }
  ],
  "predicateType": "https://in-toto.io/attestation/scai/attribute-report/v0.2",
  "predicate": {
    "attributes": [
      {
        "attribute": "PASSED_DEVELOPMENT_ENVIRONMENT",
        "evidence": {
          "name": "a1b2c3d4e5f6.development.jsonl",
          "uri": "https://example.com/scai/a1b2c3d4e5f6.development.jsonl",
          "digest": { "sha256": "d1e2f3a4b5c6..." },
          "mediaType": "application/x.dsse+json"
        }
      },
      {
        "attribute": "PASSED_SOURCE",
        "evidence": {
          "name": "a1b2c3d4e5f6.source.jsonl",
          "uri": "https://example.com/scai/a1b2c3d4e5f6.source.jsonl",
          "digest": { "sha256": "e2f3a4b5c6d1..." },
          "mediaType": "application/x.dsse+json"
        }
      },
      {
        "attribute": "PASSED_BUILD",
        "evidence": {
          "name": "a1b2c3d4e5f6.build.jsonl",
          "uri": "https://example.com/scai/a1b2c3d4e5f6.build.jsonl",
          "digest": { "sha256": "f3a4b5c6d1e2..." },
          "mediaType": "application/x.dsse+json"
        }
      },
      {
        "attribute": "PASSED_PACKAGE",
        "evidence": {
          "name": "a1b2c3d4e5f6.package.jsonl",
          "uri": "https://example.com/scai/a1b2c3d4e5f6.package.jsonl",
          "digest": { "sha256": "a4b5c6d1e2f3..." },
          "mediaType": "application/x.dsse+json"
        }
      },
      {
        "attribute": "PASSED_DEPLOY",
        "evidence": {
          "name": "a1b2c3d4e5f6.deploy.jsonl",
          "uri": "https://example.com/scai/a1b2c3d4e5f6.deploy.jsonl",
          "digest": { "sha256": "b5c6d1e2f3a4..." },
          "mediaType": "application/x.dsse+json"
        }
      }
    ],
    "producer": {
      "uri": "https://example.com/gatekeeping-attestor",
      "name": "Gatekeeping Attestor",
      "digest": {
        "sha256": "0123456789abcdef..."
      }
    }
  }
}