Support experssions when using `juniper::graphql_value`

[UkonnRa]

Say I need to convert a Custom Error into FieldError with extensions, I will do:

    #[derive(thiserror::Error, Debug, Deserialize, Serialize)]
    #[serde(tag = "type", content = "data")]
    enum SomeError {
        #[error("SomeError Item: arg1: {arg1}, arg2: {arg2}")]
        Item { arg1: String, arg2: i32 },
    }

    impl IntoFieldError for SomeError {
        fn into_field_error(self) -> juniper::FieldError {
            juniper::FieldError::new(
                "Get Some Error",
                juniper::graphql_value!({
                    "type": "SomeError",
                    "arg1": &self.arg1,
                    "arg2": &self.arg2,
                }),
            )
        }
    }

However, this will not compile, maybe because the macro does not support varients...

One walkround is:

        juniper::FieldError::new(
           "Get Some Error",
            juniper::Value::object(
                vec![
                    ("type","SomeError"),
                    ("arg1", juniper::Value::scalar(&self.arg1)),
                    ("arg2", juniper::Value::scalar(&self.arg2)),
                ]
                .into_iter()
                .collect(),
            ),
        )

But of course, it's not as clear as the former one...

[davidpdrsn]

But SomeError is an enum and doesn’t have fields arg1 and arg1. Don’t you have to match on ‘self’ to pull out the values?

[UkonnRa]

A false alarm, sorry...

[UkonnRa]

Sorry, but the fllowing code won't compile also...

#[derive(Debug, Deserialize, Serialize)]
struct SomeError;

impl SomeError {
    fn code(&self) -> String {
        "Code".to_string()
    }
}

impl IntoFieldError for SomeError {
    fn into_field_error(self) -> juniper::FieldError {
        juniper::FieldError::new(
            "Get Some Error",
            juniper::graphql_value!({
                "type": "Some Error",
                "code": self.code(),
            }),
        )
    }
}

And the error is weird:

error: expected type, found `"Some Error"`
  --> src\main.rs:54:25
   |
54 |                 "type": "Some Error",
   |                       - ^^^^^^^^^^^^ expected type
   |                       |
   |                       tried to parse a type due to this type ascription
   |
   = note: `#![feature(type_ascription)]` lets you annotate an expression with a type: `<expr>: <type>`
   = note: for more information, see https://github.com/rust-lang/rust/issues/23416

And remove "code": self.code(),, it works again

Using the latest nightly(rustc 1.42.0-nightly (6d3f4e0aa 2020-01-25))

[davidpdrsn]

Hm yeah that looks weird. I’ll look into it.

[LegNeato]

This is fairly trivial to repro locally. It can be a static call in the second position as well, it doesn't have anything to do with the "type" name either.