Added support for deserializing JSON values using the Json Extractor.

Resolves #15

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.12.1] - 2024-08-07
+
+### Added
+
+- Added support for deserializing JSON values using the [Json](https://docs.rs/picoserve/0.12.1/picoserve/extract/struct.Json.html) Extractor.
+
 ## [0.12.0] - 2024-07-22
 
 ### Breaking

Cargo.toml

@@ -21,7 +21,7 @@ exclude = [
 
 [package]
 name = "picoserve"
-version = "0.12.0"
+version = "0.12.1"
 authors = ["Samuel Hicks"]
 edition = "2021"
 rust-version = "1.75"
@@ -47,6 +47,7 @@ lhash = { version = "1.0.1", features = ["sha1"] }
 log = { version = "0.4.19", optional = true, default-features = false }
 ryu = "1.0.14"
 serde = { version = "1.0.171", default-features = false, features = ["derive"] }
+serde-json-core = "0.6.0"
 tokio = { version = "1.32.0", optional = true, features = ["io-util", "net", "time"] }
 
 [features]
@@ -56,7 +57,7 @@ alloc = []
 tokio = ["dep:tokio", "std", "serde/std"]
 embassy = ["dep:embassy-time", "dep:embassy-net"]
 
-defmt = ["dep:defmt", "embassy-net?/defmt"]
+defmt = ["dep:defmt", "embassy-net?/defmt", "serde-json-core/defmt"]
 log = ["dep:log"]
 
 [dev-dependencies]

examples/embassy/hello_world_defmt/rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
 targets = ["thumbv6m-none-eabi"]
-channel = "nightly-2023-12-20"
+channel = "nightly-2024-06-12"

examples/embassy/rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
 targets = ["thumbv6m-none-eabi"]
-channel = "nightly-2023-12-20"
+channel = "nightly-2024-06-12"

src/extract.rs

@@ -20,6 +20,14 @@ use crate::{
     ResponseSent,
 };
 
+pub mod json {
+    pub use crate::json::Json;
+
+    pub use serde_json_core::str;
+}
+
+pub use crate::json::Json;
+
 mod private {
     pub struct ViaRequest;
     pub struct ViaParts;
@@ -453,6 +461,58 @@ impl<'r, State, T: serde::de::DeserializeOwned> FromRequest<'r, State> for Form<
     }
 }
 
+#[cfg_attr(feature = "defmt", defmt::Format)]
+pub enum JsonRejection {
+    IoError,
+    DeserializationError(serde_json_core::de::Error),
+}
+
+impl IntoResponse for JsonRejection {
+    async fn write_to<R: Read, W: crate::response::ResponseWriter<Error = R::Error>>(
+        self,
+        connection: crate::response::Connection<'_, R>,
+        response_writer: W,
+    ) -> Result<ResponseSent, W::Error> {
+        match self {
+            Self::IoError => {
+                (StatusCode::INTERNAL_SERVER_ERROR, "IO Error")
+                    .write_to(connection, response_writer)
+                    .await
+            }
+            Self::DeserializationError(error) => {
+                (
+                    StatusCode::BAD_REQUEST,
+                    format_args!("Failed to parse JSON body: {error}"),
+                )
+                    .write_to(connection, response_writer)
+                    .await
+            }
+        }
+    }
+}
+
+impl<'r, State, T: serde::Deserialize<'r>, const UNESCAPE_BUFFER_SIZE: usize>
+    FromRequest<'r, State, T> for Json<T, UNESCAPE_BUFFER_SIZE>
+{
+    type Rejection = JsonRejection;
+
+    async fn from_request<R: Read>(
+        _state: &'r State,
+        _request_parts: RequestParts<'r>,
+        request_body: RequestBody<'r, R>,
+    ) -> Result<Self, Self::Rejection> {
+        serde_json_core::from_slice_escaped(
+            request_body
+                .read_all()
+                .await
+                .map_err(|_| JsonRejection::IoError)?,
+            &mut [0; UNESCAPE_BUFFER_SIZE],
+        )
+        .map(|(value, _)| Self(value))
+        .map_err(JsonRejection::DeserializationError)
+    }
+}
+
 /// Used to do reference to value conversions, mainly used with the [State] extractor to extract parts of the application state.
 pub trait FromRef<T> {
     /// Perform the reference to value conversion

src/json.rs

@@ -0,0 +1,3 @@
+/// A JSON encoded value. When serializing, the value might be serialized several times during sending, so the value must be serialized in the same way each time.
+/// When values are deserialized, `UNESCAPE_BUFFER_SIZE` is the size of the temporary buffer used for unescaping strings.
+pub struct Json<T, const UNESCAPE_BUFFER_SIZE: usize = 32>(pub T);

src/lib.rs

@@ -13,6 +13,8 @@ compile_error!("You cannot enable both tokio and embassy support");
 #[cfg(feature = "alloc")]
 extern crate alloc;
 
+mod json;
+
 #[macro_use]
 mod logging;
 

src/response/json.rs

@@ -1,11 +1,13 @@
-//! Support for serializing and deserializing JSON structures
+//! Support for serializing JSON structures
 
 use core::fmt;
 
 use serde::Serialize;
 
 use crate::io::{FormatBuffer, FormatBufferWriteError, Write};
 
+pub use crate::json::Json;
+
 #[derive(Debug)]
 struct SerializeError;
 
@@ -496,9 +498,6 @@ impl<T: serde::Serialize> super::Content for JsonBody<T> {
     }
 }
 
-/// Serializes the value in JSON form. The value might be serialized several times during sending, so the value must be serialized in the same way each time.
-pub struct Json<T>(pub T);
-
 impl<T: serde::Serialize> Json<T> {
     pub(crate) async fn do_write_to<W: Write>(&self, writer: &mut W) -> Result<(), W::Error> {
         JsonStream::new(&self.0).write_json_value(writer).await