Derive FromRow with a Vec<> field

[rogerta]

Hi there,

I am using sqlx v0.5.13 via Rocket v0.5.0-rc.2 / rocket_db_pools 0.1.0-rc.2 and asked this question there, but I was instructed to reach out here since it may be sqlx related and not Rocker related.

It seems I can't derive FromRow for my struct because of a Vec<> field.  My struct looks like this:

use rocket_db_pools::sqlx::{FromRow, sqlite::SqliteRow, Row};

#[derive(Debug, Default, Deserialize, FromRow, PartialEq, Serialize)]
pub struct App {
  pub id: i64,
  pub owner: i64,
  pub name: String,
  pub description: String,
  pub published: bool,
  #[sqlx(default)]
  pub clients: Vec<Client>,
}

I get the following compiler error at the App::from_row(row) call site, see below.  I thought the #[sqlx(default)] attribute would initialized the field to an empty vector.  What am I missing?

Compiler error:

423 |     match App::from_row(row) {
    |                ^^^^^^^^ function or associated item cannot be called on `App` due to unsatisfied trait bounds
    |
   ::: src/app.rs:85:1
    |
85  | pub struct App {
    | --------------
    | |
    | function or associated item `from_row` not found for this struct
    | doesn't satisfy `App: FromRow<'_, _>`
    |
   ::: /home/rogerta/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:400:1
    |
400 | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
    | ------------------------------------------------------------------------------------------------
    | |
    | doesn't satisfy `Vec<app::Client>: Type<_>`
    | doesn't satisfy `Vec<app::Client>: sqlx::Decode<'_, _>`
    |
    = note: the following trait bounds were not satisfied:
            `Vec<app::Client>: Type<_>`
            `Vec<app::Client>: sqlx::Decode<'_, _>`
    = note: the following trait bounds were not satisfied:
            `Vec<app::Client>: sqlx::Decode<'_, _>`
            which is required by `App: FromRow<'_, _>`
            `Vec<app::Client>: Type<_>`
            which is required by `App: FromRow<'_, _>`

Note that I am able to manually implement FromRow and it works (I'm using sqlx only with an Sqlite database), but I'd rather derive if possible:

use rocket_db_pools::sqlx::{FromRow, sqlite::SqliteRow, Row};

#[derive(Debug, Default, Deserialize, PartialEq, Serialize)]
pub struct App {
  pub id: i64,
  pub owner: i64,
  pub name: String,
  pub description: String,
  pub published: bool,
  pub clients: Vec<Client>,
}

impl FromRow<'_, SqliteRow> for App {
  fn from_row(row: &SqliteRow) -> std::result::Result<Self, sqlx::Error> {
    Ok(Self {
      id: row.try_get("id")?,
      owner: row.try_get("owner")?,
      name: row.try_get("name")?,
      description: row.try_get("description")?,
      published: row.try_get("published")?,
      clients: Vec::default(),
    })
  }
}

Thanks.

[lthoerner]

I am having this same issue. This is a pretty common pattern and it would be a really nice feature. I'd be happy to help work on it but I'm not sure where to begin.