async_graphql_test/matchers/
should_be_null.rs

1use async_graphql::async_trait::async_trait;
2use async_graphql::{Context, CustomDirective, Directive, ResolveFut, ServerResult, Value};
3
4use super::MatcherError;
5
6/// Use `@shouldBeNull` when you want to check that something is null.
7#[Directive(location = "Field", name = "shouldBeNull")]
8pub fn should_be_null() -> impl CustomDirective {
9    ShouldBeNull
10}
11
12struct ShouldBeNull;
13
14#[async_trait]
15impl CustomDirective for ShouldBeNull {
16    async fn resolve_field(
17        &self,
18        ctx: &Context<'_>,
19        resolve: ResolveFut<'_>,
20    ) -> ServerResult<Option<Value>> {
21        match resolve.await {
22            Ok(None) => Ok(None),
23            Ok(Some(Value::Null)) => Ok(Some(Value::Null)),
24            Ok(Some(other)) => Err(MatcherError::new(
25                ctx.item.pos,
26                format!("Expected: null\nReceived: {other}"),
27            )),
28            Err(mut err) => {
29                err.message = format!("Expected null, thrown error instead:\n\n{}", err.message);
30                err.source = Some(std::sync::Arc::new(MatcherError));
31                Err(err)
32            }
33        }
34    }
35}

async_graphql_test/matchers/should_be_null.rs

async_graphql_test/matchers/
should_be_null.rs