We're trying to return structure in RPC, but as far as I understand it should be serializable:
error[E0277]: the trait bound `pallet_spaces::Space<T>: serde::de::Deserialize<'_>` is not satisfied
--> pallets/spaces/rpc/src/lib.rs:15:1
|
15 | #[rpc]
| ^^^^^^ the trait `serde::de::Deserialize<'_>` is not implemented for `pallet_spaces::Space<T>`
|
= note: required because of the requirements on the impl of `for<'de> serde::de::Deserialize<'de>` for `std::vec::Vec<pallet_spaces::Space<T>>`
= note: required because of the requirements on the impl of `serde::de::DeserializeOwned` for `std::vec::Vec<pallet_spaces::Space<T>>`
= note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)
The problem is that we use T::Moment from pallet_timestamp and it's not serializable, so we stuck at this point:
error[E0277]: the trait bound `<T as pallet_timestamp::Trait>::Moment: _::_serde::Serialize` is not satisfied
--> pallets/spaces/src/lib.rs:25:5
|
25 | pub created: WhoAndWhen<T>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `_::_serde::Serialize` is not implemented for `<T as pallet_timestamp::Trait>::Moment`
|
= note: required because of the requirements on the impl of `_::_serde::Serialize` for `pallet_utils::WhoAndWhen<T>`
= note: required by `_::_serde::ser::SerializeStruct::serialize_field`
What can you suggest to easily return a structure like this?
#[derive(Encode, Decode, Clone, Eq, PartialEq, RuntimeDebug, Serialize, Deserialize)]
pub struct Space<T: Trait> {
pub id: SpaceId,
pub created: WhoAndWhen<T>,
pub updated: Option<WhoAndWhen<T>>,
pub owner: T::AccountId,
// Can be updated by the owner:
pub parent_id: Option<SpaceId>,
pub handle: Option<Vec<u8>>,
pub content: Content,
pub hidden: bool,
pub posts_count: u32,
pub hidden_posts_count: u32,
pub followers_count: u32,
pub score: i32,
/// Allows to override the default permissions for this space.
pub permissions: Option<SpacePermissions>,
}
#[derive(Encode, Decode, Clone, Eq, PartialEq, RuntimeDebug, Serialize, Deserialize)]
pub struct WhoAndWhen<T: Trait> {
pub account: T::AccountId,
pub block: T::BlockNumber,
pub time: T::Moment,
}
Your main problem is that you are mixing std and no-std here. Substrate only depends on serde in std mode, as you can learn about in literally any Cargo.toml file in the project.
Start by fixing this: You only derive serde::* when you are in std mode.
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
#[derive(Encode, Decode, Clone, Eq, PartialEq, RuntimeDebug)]
pub struct Space<T: Trait> {
// snip..
}
Related
I'm trying to use Async Graphql, I want to use sqlx json type in model. In normal api operations the code is running. But when I want to use the async graphql InputObject macro, I get an error. The codes I used are as follows, I couldn't find a solution for the problem.
#[derive(Serialize, Deserialize, Debug, Clone, sqlx::Type)]
#[sqlx(transparent)]
pub struct Meta(Map<String, Value>);
scalar!(Meta);
#[derive(Debug, Serialize, Deserialize, Clone, FromRow, SimpleObject)]
pub struct User {
#[serde(skip_serializing)]
#[graphql(skip)]
pub id: Uuid,
pub name: String,
pub email: String,
#[serde(skip_serializing)]
#[graphql(skip)]
pub password: String,
#[serde(skip_serializing)]
#[graphql(skip)]
pub meta: Json<Meta>,
pub created_at: DateTime<Utc>,
pub updated_at: DateTime<Utc>,
}
No problem so far. But the code below gives an error.
#[derive(Debug, Deserialize, Validate, InputObject)]
pub struct RegisterInput {
#[validate(length(min = 4, max = 10))]
pub name: String,
#[validate(email)]
pub email: String,
#[validate(length(min = 6))]
pub password: String,
pub meta: Json<Meta>,
}
InputObject error.
error[E0277]: the trait bound `sqlx::types::Json<Meta>: InputType` is not satisfied
--> src/dto.rs:13:40
|
13 | #[derive(Debug, Deserialize, Validate, InputObject)]
| ^^^^^^^^^^^ the trait `InputType` is not implemented for `sqlx::types::Json<Meta>`
|
= help: the following other types implement trait `InputType`:
Arc<T>
Arc<[T]>
Arc<str>
BTreeMap<K, V>
BTreeSet<T>
Box<T>
Box<[T]>
Box<str>
and 49 others
= note: this error originates in the derive macro `InputObject` (in Nightly builds, run with -Z macro-backtrace for more info)
Can you help on the subject?
I have the following two structs for which I derive serde traits.
use serde::{Serialize, Deserialize};
#[derive(Serialize, Deserialize)]
pub struct Item<'a> {
pub id: &'a str,
pub name: &'a str
}
#[derive(Serialize, Deserialize)]
struct Set<'a> {
items: Vec<Item<'a>>
}
When I try to compile this, I am getting am getting the following error message to ensure that lifetime parameter 'de from Deserialize needs to outlife lifetime parameter 'a:
15 | #[derive(Serialize, Deserialize)]
| ----------- lifetime `'de` defined here
16 | struct Set<'a> {
| -- lifetime `'a` defined here
17 | sets: Vec<Item<'a>>
| ^^^^ requires that `'de` must outlive `'a`
|
= help: consider adding the following bound: `'de: 'a`
But when I add the required bound as follows, I am getting an error message that 'de is not used.
use serde::{Serialize, Deserialize};
#[derive(Serialize, Deserialize)]
pub struct Item<'a> {
pub id: &'a str,
pub name: &'a str
}
#[derive(Serialize, Deserialize)]
struct Set<'a, 'de: 'a> {
items: Vec<Item<'a>>
}
16 | struct Set<'a, 'de: 'a> {
| ^^^ unused parameter
|
= help: consider removing `'de`, referring to it in a field, or using a marker such as `PhantomData`
How can I fix this?
You need to add #[serde(borrow)] to the sets field:
#[derive(Serialize, Deserialize)]
struct Set<'a> {
#[serde(borrow)]
items: Vec<Item<'a>>,
}
This will bound the 'de lifetime in the generated code on 'a. Note that this happens implicitly for fields of type &str or &[u8], but for anything else you need to expicitly request the trait bound.
I'm trying to export the following struct:
#[wasm_bindgen]
#[derive(Eq, PartialEq, Debug, Clone)]
pub enum TokenType {
KeywordLiteral,
NumberLiteral,
Operator,
Separator,
StringLiteral,
}
#[wasm_bindgen]
#[derive(Eq, PartialEq, Debug, Clone)]
pub struct Token {
pub typ: TokenType,
pub val: String,
}
but I'm getting:
error[E0277]: the trait bound `token::TokenType: std::marker::Copy` is not satisfied
--> src\tokenizer\token.rs:17:14
|
14 | #[wasm_bindgen]
| --------------- required by this bound in `__wbg_get_token_typ::assert_copy`
...
17 | pub typ: TokenType,
| ^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `token::TokenType`
as well as:
error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
--> src\tokenizer\token.rs:18:14
|
14 | #[wasm_bindgen]
| --------------- required by this bound in `__wbg_get_token_val::assert_copy`
...
18 | pub val: String,
I can add #[derive(Copy)] to TokenType but not to String.
I'm new to rust so help is really appreciated.
According to wasm-bindgen#1985, public fields of structs are required to be Copy in order for the automatically generated accessors to function.
You can either make the fields private, or annotate them with #[wasm_bindgen(skip)], and then implement a getter and setter directly.
There is an example provided in wasm-bindgen's docs describing how to write these:
#[wasm_bindgen]
pub struct Baz {
field: i32,
}
#[wasm_bindgen]
impl Baz {
#[wasm_bindgen(constructor)]
pub fn new(field: i32) -> Baz {
Baz { field }
}
#[wasm_bindgen(getter)]
pub fn field(&self) -> i32 {
self.field
}
#[wasm_bindgen(setter)]
pub fn set_field(&mut self, field: i32) {
self.field = field;
}
}
When objects are shared between wasm and js, the js object only contains the pointer to the struct inside the wasm runtime's memory. When you access fields from JS, it goes through a defined property which makes a function call to the wasm code asking it for the property value (you can think of the wasm memory as a bit UInt8Array).
Requiring the objects to be Copy is probably done to avoid surprises when auto-generating these getters and setters. If you implement them manually, you can have the same behaviour in JS and be able to control what's being set on the rust side.
I am trying to declare a struct that contains another struct of any given type that can be Deserialize and Serialize.
#[derive(Debug, Serialize, Deserialize)]
pub struct Foo<T: Deserialize + Serialize> {
pub data: T,
}
Rust playground.
For that, I have tried to use trait bounds, using traits such as DeserializeOwned or Deserialize. Both have failed at compilation time with the following errors:
error[E0283]: type annotations required: cannot resolve `T: serde::Deserialize<'de>`
--> src/main.rs:9:28
|
9 | #[derive(Debug, Serialize, Deserialize)]
| ^^^^^^^^^^^
|
= note: required by `serde::Deserialize`
error[E0637]: `&` without an explicit lifetime name cannot be used here
--> src/main.rs:10:19
|
10 | pub struct Foo<T: Deserialize + Serialize> {
| ^^^^^^^^^^^ explicit lifetime name needed here
I faced errors trying to add a lifetime since I am not using storing a reference but a value.
What is the most idiomatic way of declaring this type of struct?
Just don't place the bounds on the type:
use serde::{Deserialize, Serialize}; // 1.0.91
#[derive(Debug, Serialize, Deserialize)]
pub struct Foo<T> {
pub data: T,
}
#[derive(Debug, Serialize, Deserialize)]
pub struct Boo {
pub a: i64,
}
fn main() {
let data = Boo { a: 1 };
let wrap = Foo { data };
println!("{:?}", wrap);
}
Then, place the bounds on methods where you need that behavior:
fn use_it<T>(foo: Foo<T>)
where
Foo<T>: Serialize,
{
// ...
}
I found a solution thanks to a member of the Rust Discord who referred me to the following Github issue. The trick is not to use trait bounds but attribute bounds.
#[derive(Debug, Serialize, Deserialize)]
pub struct Foo<T> {
#[serde(bound(
serialize = "T: Serialize",
deserialize = "T: Deserialize<'de>",
))]
pub data: T,
}
I have the following model:
use diesel::prelude::*;
use crate::schema::category;
#[derive(Debug, Identifiable, Queryable)]
#[table_name = "category"]
pub struct Category {
pub id: i64,
pub name: String,
pub description: String,
pub parent_id: Option<i64>,
}
#[derive(Debug, Insertable)]
#[table_name = "category"]
pub struct NewCategory<'a> {
pub name: &'a str,
pub description: &'a str,
pub parent_id: &'a Option<i64>,
}
and schema.rs:
table! {
category (id) {
id -> Integer,
name -> Text,
description -> Text,
parent_id -> Nullable<Integer>,
}
}
However, when I try to compile this code, I get the following errors:
error[E0277]: the trait bound `std::option::Option<i64>: diesel::Expression` is not satisfied
--> src/models/categories.rs:15:17
|
15 | #[derive(Debug, Insertable)]
| ^^^^^^^^^^ the trait `diesel::Expression` is not implemented for `std::option::Option<i64>`
|
= note: required because of the requirements on the impl of `diesel::Expression` for `&std::option::Option<i64>`
error[E0277]: the trait bound `std::option::Option<i64>: diesel::Expression` is not satisfied
--> src/models/categories.rs:15:17
|
15 | #[derive(Debug, Insertable)]
| ^^^^^^^^^^ the trait `diesel::Expression` is not implemented for `std::option::Option<i64>`
|
= note: required because of the requirements on the impl of `diesel::Expression` for `&'a std::option::Option<i64>`
What do I need to get this to work? I've looked around, but the only similar issue that I've found is when someone had more than 16 columns in their table, which is not the case here.
Modify pub parent_id: &'a Option<i64> to place the &'a inside of the Option: pub parent_id: Option<&'a i64>.