A way to use VersionOf and AnyVersion given reference to a struct

[iilyak]

Currently it doesn't seem to be possible to determine current version of a struct given a reference to a struct (clone() is not an option for the struct I have).

[doctorn]

I'm not sure I understand. Could you explain a little more? Maybe provide some code you'd like to work that doesn't?

[iilyak]

My original problem is to detect the fact that configuration file need to be updated. The idea is to use the version of the file encoded in the vsn field of a top level struct and compare it with versions of all structs used in the configuration.

In order to do that I need to visit each node of the tree and collect versions of the struct involved.

It has been a challenge because obake doesn't support types with generics which means container types are not working out of the box.

Here is some code showing the configuration structure

#[derive(Deserialize, Serialize, Debug, Default, PartialEq, Validate)]
#[obake::versioned]
#[obake(derive(serde::Serialize, serde::Deserialize))]
#[obake(version("0.0.1"))]
pub struct ConfigFile {
  pub vsn: u16,
  #[serde(with = "humantime_serde")]
  #[serde(skip_serializing_if = "Option::is_none")]
  #[serde(default)]
  pub delay: Option<Duration>,
  // I cannot use obake(version(xxx)) on container type
  pub profiles: Vec<Profile>,
}

#[obake::versioned]
#[obake(derive(serde::Serialize, serde::Deserialize, PartialEq, Debug))]
#[obake(version("0.0.3"))]
#[derive(Validate, serde::Deserialize, serde::Serialize, PartialEq, Debug)]
pub struct Profile {
  pub id: String,
  pub name: String,
}

I wanted to write a helper function for each struct which would return the greatest version

impl ConfigFile {
  pub fn vsn(self&) -> Version {
    // p in map function bellow has type &Profile_v0_0_1
    let profiles_vsn = self.profiles
      .first()
      .map(|p|
        Version::parse(<VersionedProfile as VersionTagged<Profile>>::version_str(p))
        .unwrap_or(Version::from("0.0.0")));

  }

}

The code above fails

331 | ...on::parse(<VersionedProfile as VersionTagged<Profile>>::version_str(p)).unwrap_or(Version::from("0.0.0")));
    |              --------------------------------------------------------- ^ expected `&VersionedProfile`, found `&Profile_v0_0_1`
    |              |
    |              arguments to this function are incorrect
    |
    = note: expected reference `&VersionedProfile`
               found reference `&Profile_v0_0_1`

  pub fn vsn(&self) -> Version {
    // p in map function bellow has type &Profile_v0_0_1
    let profiles_vsn = self.profiles.first().map(|p|{
        let v: obake::AnyVersion<Profile> = p.into();
        Version::parse(v.version_str)
    });
  }

The above fails with

334 |         let v: obake::AnyVersion<Profile> = p.into();
    |                                               ^^^^ the trait `From<&Profile_v0_0_1>` is not implemented for `VersionedProfile`
    |
    = note: required for `&Profile_v0_0_1` to implement `Into<VersionedProfile>`

  pub fn vsn(&self) -> Version {
    // p in map function bellow has type &Profile_v0_0_1
    let profiles_vsn = self.profiles.first().map(|p| {
      let v: obake::AnyVersion<Profile> = (*p).into();
      Version::parse(v.version_str())
    });
    profiles_vsn.unwrap().unwrap()
  }

The above fails

334 |       let v: obake::AnyVersion<Profile> = (*p).into();
    |                                           ^^^^ ------ `*p` moved due to this method call
    |                                           |
    |                                           move occurs because `*p` has type `Profile_v0_0_1`, which does not implement the `Copy` trait
    |
note: `into` takes ownership of the receiver `self`, which moves `*p`

As you can see there is no easy way to get the version. The following works

impl ConfigFile {
  pub fn version(&self) -> Version {
    Version::parse(Self::VERSION).expect("expect ConfigFile to be versioned")
  }

  pub fn vsn(&self) -> Version {
    let inner = self.profiles.first().map(|p| p.vsn());
    let inner = inner.unwrap();
    if inner < self.version() {
      self.version()
    } else {
      inner
    }
  }
}

impl Profile {
  pub fn version(&self) -> Version {
    Version::parse(Self::VERSION).expect("expect Profile to be versioned")
  }
  pub vsn(&self) -> Version {
      self.version()
  }
}