A few small refactorings (#655)

* Simplify json content-type check

* Import HeaderMap from http instead of from headers

The headers crate is an optional dependency and its HeaderMap re-export
is `#[doc(hidden)]`.

* Use headers re-export in axum in examples

axum/src/docs/extract.md

@@ -40,12 +40,12 @@ Some commonly used extractors are:
 use axum::{
     extract::{Json, TypedHeader, Path, Extension, Query},
     routing::post,
+    headers::UserAgent,
     http::{Request, header::HeaderMap},
     body::{Bytes, Body},
     Router,
 };
 use serde_json::Value;
-use headers::UserAgent;
 use std::collections::HashMap;
 
 // `Path` gives you the path parameters and deserializes them. See its docs for
@@ -148,10 +148,10 @@ individual headers first:
 use axum::{
     extract::TypedHeader,
     routing::get,
+    headers::UserAgent,
     http::header::HeaderMap,
     Router,
 };
-use headers::UserAgent;
 
 async fn handler(
     TypedHeader(user_agent): TypedHeader<UserAgent>,

axum/src/extract/typed_header.rs

@@ -14,10 +14,10 @@ use std::ops::Deref;
 /// ```rust,no_run
 /// use axum::{
 ///     extract::TypedHeader,
+///     headers::UserAgent,
 ///     routing::get,
 ///     Router,
 /// };
-/// use headers::UserAgent;
 ///
 /// async fn users_teams_show(
 ///     TypedHeader(user_agent): TypedHeader<UserAgent>,

axum/src/json.rs

@@ -132,7 +132,7 @@ fn json_content_type<B>(req: &RequestParts<B>) -> Result<bool, HeadersAlreadyExt
     };
 
     let is_json_content_type = mime.type_() == "application"
-        && (mime.subtype() == "json" || mime.suffix().filter(|name| *name == "json").is_some());
+        && (mime.subtype() == "json" || mime.suffix().map_or(false, |name| name == "json"));
 
     Ok(is_json_content_type)
 }

axum/src/routing/tests/get_to_head.rs

@@ -4,7 +4,7 @@ use tower::ServiceExt;
 
 mod for_handlers {
     use super::*;
-    use headers::HeaderMap;
+    use http::HeaderMap;
 
     #[tokio::test]
     async fn get_handles_head() {

examples/jwt/src/main.rs

@@ -9,12 +9,12 @@
 use axum::{
     async_trait,
     extract::{FromRequest, RequestParts, TypedHeader},
+    headers::{authorization::Bearer, Authorization},
     http::StatusCode,
     response::{IntoResponse, Response},
     routing::{get, post},
     Json, Router,
 };
-use headers::{authorization::Bearer, Authorization};
 use jsonwebtoken::{decode, encode, DecodingKey, EncodingKey, Header, Validation};
 use once_cell::sync::Lazy;
 use serde::{Deserialize, Serialize};