`serde(default)` and `KubeSchema` - no function or associated item named `default`

[tmsdce]

Current and expected behavior

Hi,

First, thank you for your work on this crate, building k8s-related stuff with it is really nice

I'd like to use CEL related configuration in my CRD but it seems like KubeSchema doesn't play well with #[serde(default)].

Given the following code:

fn main() {
    println!("{}", serde_yaml::to_string(&MyCrd::crd()).unwrap());
}

#[derive(CustomResource, Deserialize, Serialize, Clone, Debug, KubeSchema)]
#[kube(kind = "MyCrd", group = "mygroup.io", version = "v1", namespaced)]
#[serde(rename_all = "camelCase")]
#[serde(default)]
struct MyCrdSpec {
    field_one: String,
    field_two: String,
}

impl Default for MyCrdSpec {
    fn default() -> Self {
        Self {
            field_one: "default_value_1".to_string(),
            field_two: "default_value_2".to_string(),
        }
    }
}

This fails to compile:

error[E0599]: no function or associated item named `default` found for struct `MyCrdSpecValidated` in the current scope
  --> src/main.rs:9:64
   |
9  | #[derive(CustomResource, Deserialize, Serialize, Clone, Debug, KubeSchema)]
   |                                                                ^^^^^^^^^^ function or associated item not found in `MyCrdSpecValidated`
...
13 | pub struct MyCrdSpec {
   | -------------------- function or associated item `default` not found for this struct
   |
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `default`, perhaps you need to implement it:
           candidate #1: `Default`
   = note: this error originates in the derive macro `::schemars::JsonSchema` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0599`.

Using JsonSchema instead of KubeSchema makes this code compile, but you can't use CEL related configuration.

The workaround I found for now is not using the Default trait implementation at all (and not using the #[serde(default)] attribute on the struct), but defining default functions for each field of my struct, like so:

#[derive(CustomResource, Deserialize, Serialize, Clone, Debug, KubeSchema)]
#[kube(kind = "MyCrd", group = "mygroup.io", version = "v1", namespaced)]
#[serde(rename_all = "camelCase")]
struct MyCrdSpec {
    #[serde(default = "MyCrdSpec::default_for_field_one")]
    field_one: String,
    #[serde(default = "MyCrdSpec::default_for_field_two")]
    field_two: String,
}

impl MyCrdSpec {
    fn default_for_field_one() -> String {
        "default_value_1".to_string()
    }
    fn default_for_field_two() -> String {
        "default_value_2".to_string()
    }
}

This compiles fine but can quickly become cumbersome as you add fields with more complex types.

Possible solution

No response

Additional context

This issue seems related to #1746

Environment

Kubectl version

Client Version: v1.30.3
Kustomize Version: v5.0.4-0.20230601165947-6ce0bf390ce3
Server Version: v1.33.1

Configuration and features

k8s-openapi = { version = "0.25.0", features = ["v1_33", "schemars"] }
kube = { version = "1.1.0", features = ["runtime", "derive"] }
schemars = { version = "0.8", features = ["chrono"] }
serde = { version = "1.0.219", features = ["derive"] }
serde_json = "1.0.140"
serde_yaml = "0.9.34"

Affected crates

No response

Would you like to work on fixing this bug?

None