async_graphql/
subscription.rs

1use std::{borrow::Cow, pin::Pin};
2
3use futures_util::stream::{Stream, StreamExt};
4
5use crate::{
6    parser::types::Selection, registry, registry::Registry, Context, ContextSelectionSet,
7    PathSegment, Response, ServerError, ServerResult,
8};
9
10/// A GraphQL subscription object
11pub trait SubscriptionType: Send + Sync {
12    /// Type the name.
13    fn type_name() -> Cow<'static, str>;
14
15    /// Qualified typename.
16    fn qualified_type_name() -> String {
17        format!("{}!", Self::type_name())
18    }
19
20    /// Create type information in the registry and return qualified typename.
21    fn create_type_info(registry: &mut registry::Registry) -> String;
22
23    /// This function returns true of type `EmptySubscription` only.
24    #[doc(hidden)]
25    fn is_empty() -> bool {
26        false
27    }
28
29    #[doc(hidden)]
30    fn create_field_stream<'a>(
31        &'a self,
32        ctx: &'a Context<'_>,
33    ) -> Option<Pin<Box<dyn Stream<Item = Response> + Send + 'a>>>;
34}
35
36pub(crate) type BoxFieldStream<'a> = Pin<Box<dyn Stream<Item = Response> + 'a + Send>>;
37
38pub(crate) fn collect_subscription_streams<'a, T: SubscriptionType + 'static>(
39    ctx: &ContextSelectionSet<'a>,
40    root: &'a T,
41    streams: &mut Vec<BoxFieldStream<'a>>,
42) -> ServerResult<()> {
43    for selection in &ctx.item.node.items {
44        if let Selection::Field(field) = &selection.node {
45            streams.push(Box::pin({
46                let ctx = ctx.clone();
47                async_stream::stream! {
48                    let ctx = ctx.with_field(field);
49                    let field_name = ctx.item.node.response_key().node.clone();
50                    let stream = root.create_field_stream(&ctx);
51                    if let Some(mut stream) = stream {
52                        while let Some(resp) = stream.next().await {
53                            yield resp;
54                        }
55                    } else {
56                        let err = ServerError::new(format!(r#"Cannot query field "{}" on type "{}"."#, field_name, T::type_name()), Some(ctx.item.pos))
57                            .with_path(vec![PathSegment::Field(field_name.to_string())]);
58                        yield Response::from_errors(vec![err]);
59                    }
60                }
61            }))
62        }
63    }
64    Ok(())
65}
66
67impl<T: SubscriptionType> SubscriptionType for &T {
68    fn type_name() -> Cow<'static, str> {
69        T::type_name()
70    }
71
72    fn create_type_info(registry: &mut Registry) -> String {
73        T::create_type_info(registry)
74    }
75
76    fn create_field_stream<'a>(
77        &'a self,
78        ctx: &'a Context<'_>,
79    ) -> Option<Pin<Box<dyn Stream<Item = Response> + Send + 'a>>> {
80        T::create_field_stream(*self, ctx)
81    }
82}
async_graphql/subscription.rs

async_graphql/
subscription.rs
