Flattened untagged enums lead to invalid CRDs

[NickLarsenNZ]

Current and expected behavior

Current bahaviour:

#[derive(CustomResource, Serialize, Deserialize, Debug, Clone, JsonSchema)]
#[kube(group = "clux.dev", version = "v1", kind = "FlattenedUntaggedEnumTest")]
struct FlattenedUntaggedEnumTestSpec {
    foo: FlattenedUntaggedEnum,
}

/// An untagged enum with a nested enum inside
#[derive(Serialize, Deserialize, Debug, Clone, JsonSchema)]
#[serde(untagged)]
enum UntaggedEnum {
    /// Used in case the `one` field of type [`u32`] is present
    /// This should not appear in the schema because the "variant" disappears
    /// and this comment cannot pertain to all fields within the struct variant.
    A { one: String },
    /// Used in case the `two` field of type [`NormalEnum`] is present
    /// This should not appear in the schema because the "variant" disappears
    /// and this comment cannot pertain to all fields within the struct variant.
    B { two: NormalEnum, three: String },
    /// Used in case no fields are present
    C {},
}

/// Put a [`UntaggedEnum`] behind `#[serde(flatten)]`
#[derive(Serialize, Deserialize, Debug, Clone, JsonSchema)]
struct FlattenedUntaggedEnum {
    #[serde(flatten)]
    inner: UntaggedEnum,
}

Invalid CRD

{
  "apiVersion": "apiextensions.k8s.io/v1",
  "kind": "CustomResourceDefinition",
  "metadata": {
    "name": "flatteneduntaggedenumtests.clux.dev"
  },
  "spec": {
    "group": "clux.dev",
    "names": {
      "categories": [],
      "kind": "FlattenedUntaggedEnumTest",
      "plural": "flatteneduntaggedenumtests",
      "shortNames": [],
      "singular": "flatteneduntaggedenumtest"
    },
    "scope": "Cluster",
    "versions": [
      {
        "additionalPrinterColumns": [],
        "name": "v1",
        "schema": {
          "openAPIV3Schema": {
            "description": "Auto-generated derived type for FlattenedUntaggedEnumTestSpec via `CustomResource`",
            "properties": {
              "spec": {
                "properties": {
                  "foo": {
                    "anyOf": [
                      {
                        "required": [
                          "one"
                        ]
                      },
                      {
                        "required": [
                          "three",
                          "two"
                        ]
                      },
                      {
                        "description": "Used in case no fields are present",
                        "type": "object"
                      }
                    ],
                    "description": "Put a [`UntaggedEnum`] behind `#[serde(flatten)]`",
                    "properties": {
                      "one": {
                        "description": "Used in case the `one` field of type [`u32`] is present\nThis should not appear in the schema because the \"variant\" disappears\nand this comment cannot pertain to all fields within the struct variant.",
                        "type": "string"
                      },
                      "three": {
                        "type": "string"
                      },
                      "two": {
                        "description": "A very simple enum with unit variants",
                        "enum": [
                          "C",
                          "D",
                          "A",
                          "B"
                        ],
                        "type": "string"
                      }
                    },
                    "type": "object"
                  }
                },
                "required": [
                  "foo"
                ],
                "type": "object"
              }
            },
            "required": [
              "spec"
            ],
            "title": "FlattenedUntaggedEnumTest",
            "type": "object"
          }
        },
        "served": true,
        "storage": true,
        "subresources": {}
      }
    ]
  }
}

When applied to Kubernetes, the following errors are given:

The CustomResourceDefinition "flatteneduntaggedenumtests.clux.dev" is invalid: 
* spec.validation.openAPIV3Schema.properties[spec].properties[foo].anyOf[2].description: Forbidden: must be empty to be structural
* spec.validation.openAPIV3Schema.properties[spec].properties[foo].anyOf[2].type: Forbidden: must be empty to be structural

Expected behaviour

This test should pass

Notice the empty {} under the anyOf.

#[test]
fn flattened_untagged_enum() {
    assert_json_eq!(
        FlattenedUntaggedEnumTest::crd(),
        json!(
          {
            "apiVersion": "apiextensions.k8s.io/v1",
            "kind": "CustomResourceDefinition",
            "metadata": {
              "name": "flatteneduntaggedenumtests.clux.dev"
            },
            "spec": {
              "group": "clux.dev",
              "names": {
                "categories": [],
                "kind": "FlattenedUntaggedEnumTest",
                "plural": "flatteneduntaggedenumtests",
                "shortNames": [],
                "singular": "flatteneduntaggedenumtest"
              },
              "scope": "Cluster",
              "versions": [
                {
                  "additionalPrinterColumns": [],
                  "name": "v1",
                  "schema": {
                    "openAPIV3Schema": {
                      "description": "Auto-generated derived type for FlattenedUntaggedEnumTestSpec via `CustomResource`",
                      "properties": {
                        "spec": {
                          "properties": {
                            "foo": {
                              "anyOf": [
                                {
                                  "required": [
                                    "one"
                                  ]
                                },
                                {
                                  "required": [
                                    "three",
                                    "two"
                                  ]
                                },
                                {}
                              ],
                              "description": "Put a [`UntaggedEnum`] behind `#[serde(flatten)]`",
                              "properties": {
                                "one": {
                                  "type": "string"
                                },
                                "two": {
                                  "description": "A very simple enum with unit variants",
                                  "enum": [
                                    "C",
                                    "D",
                                    "A",
                                    "B"
                                  ],
                                  "type": "string"
                                },
                                "three": {
                                  "type": "string"
                                }
                              },
                              "type": "object"
                            }
                          },
                          "required": [
                            "foo"
                          ],
                          "type": "object"
                        }
                      },
                      "required": [
                        "spec"
                      ],
                      "title": "FlattenedUntaggedEnumTest",
                      "type": "object"
                    }
                  },
                  "served": true,
                  "storage": true,
                  "subresources": {}
                }
              ]
            }
          }
        )
    );
}

Which fails with:

json atom at path ".spec.versions[0].schema.openAPIV3Schema.properties.spec.properties.foo.properties.one.description" is missing from rhs

json atom at path ".spec.versions[0].schema.openAPIV3Schema.properties.spec.properties.foo.anyOf[2].type" is missing from rhs

json atom at path ".spec.versions[0].schema.openAPIV3Schema.properties.spec.properties.foo.anyOf[2].description" is missing from rhs

Possible solution

This is another one that was fixed properly in #1839.
Specifically:

https://github.com/stackabletech/kube-rs/blob/71707abf1109bad01bbf2c46e3b161846049767a/kube-core/src/schema/transform_properties.rs#L89-L95

Additional context

No response

Environment

N/A

Configuration and features

No response

YAML

No response

Affected crates

No response

Would you like to work on fixing this bug?

yes

[NickLarsenNZ]

I'm seeing if I can do a minimal fix, but there are two issues in this one:

• The empty object representation still has a type and description (not allowed in anyOf subschemas).
• Untagged variant descriptions make no sense in the schema, and currently they end up on the inner field for struct variants. They should be dropped in that case.

If the minimal fix is too cumbersome, I would ask @clux that we just replace the properties hoisting with the one I did in #1839 (given I have already spent so much time on a complete fix and these issues keep affecting us and minimal fixes are becoming too time consuming).

[NickLarsenNZ]

Can confirm the PropertiesSchemaRewriter from #1839 fixes both issues without modification, and fixes another issue regarding doc-comment overrides.

Ignoring the doc-comment override issue for now, I will give a minimal fix one more try. It appears like it will end up requiring more refactoring than what I just tried.

[NickLarsenNZ]

#1942 contains the minimal fix.

Once merged, I would be happy to raise a PR for refactoring the properties hoisting based on #1839.