routing/bedrock/
lazy_get.rs

1// Copyright 2024 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use super::dict_ext::request_with_dictionary_replacement;
6use crate::{DictExt, RoutingError};
7use async_trait::async_trait;
8use cm_types::IterablePath;
9use moniker::ExtendedMoniker;
10use router_error::RouterError;
11use sandbox::{CapabilityBound, Dict, Request, Routable, Router, RouterResponse};
12use std::fmt::Debug;
13
14/// Implements the `lazy_get` function for [`Routable<Dict>`].
15pub trait LazyGet<T: CapabilityBound>: Routable<Dict> {
16    /// Returns a router that requests a dictionary from the specified `path` relative to
17    /// the base routable or fails the request with `not_found_error` if the member is not
18    /// found.
19    fn lazy_get<P>(self, path: P, not_found_error: RoutingError) -> Router<T>
20    where
21        P: IterablePath + Debug + 'static;
22}
23
24impl<R: Routable<Dict> + 'static, T: CapabilityBound> LazyGet<T> for R {
25    fn lazy_get<P>(self, path: P, not_found_error: RoutingError) -> Router<T>
26    where
27        P: IterablePath + Debug + 'static,
28    {
29        #[derive(Debug)]
30        struct ScopedDictRouter<P: IterablePath + Debug + 'static> {
31            router: Router<Dict>,
32            path: P,
33            not_found_error: RoutingError,
34        }
35
36        #[async_trait]
37        impl<P: IterablePath + Debug + 'static, T: CapabilityBound> Routable<T> for ScopedDictRouter<P> {
38            async fn route(
39                &self,
40                request: Option<Request>,
41                debug: bool,
42            ) -> Result<RouterResponse<T>, RouterError> {
43                // If `debug` is true, that should only apply to the capability at `path`.
44                // Here we're looking up the containing dictionary, so set `debug = false`, to
45                // obtain the actual Dict and not its debug info.
46                let init_request = if self.path.iter_segments().count() > 1 {
47                    request_with_dictionary_replacement(request.as_ref())?
48                } else {
49                    request.as_ref().map(|r| r.try_clone()).transpose()?
50                };
51                match self.router.route(init_request, false).await? {
52                    RouterResponse::<Dict>::Capability(dict) => {
53                        let moniker: ExtendedMoniker = self.not_found_error.clone().into();
54                        let resp =
55                            dict.get_with_request(&moniker, &self.path, request, debug).await?;
56                        let resp =
57                            resp.ok_or_else(|| RouterError::from(self.not_found_error.clone()))?;
58                        let resp = resp.try_into().map_err(|debug_name: &'static str| {
59                            RoutingError::BedrockWrongCapabilityType {
60                                expected: T::debug_typename().into(),
61                                actual: debug_name.into(),
62                                moniker,
63                            }
64                        })?;
65                        return Ok(resp);
66                    }
67                    _ => Err(RoutingError::BedrockMemberAccessUnsupported {
68                        moniker: self.not_found_error.clone().into(),
69                    }
70                    .into()),
71                }
72            }
73        }
74
75        Router::<T>::new(ScopedDictRouter {
76            router: Router::<Dict>::new(self),
77            path,
78            not_found_error: not_found_error.into(),
79        })
80    }
81}
routing/bedrock/lazy_get.rs

routing/bedrock/
lazy_get.rs
