Use compile_error if no http features are enabled

- Provide help so people know that they have to enable a feature.
- Put imports in place so conditional compilation doesn't try to compile unnecesary code.

Signed-off-by: David Calavera <[email protected]>

Author: calavera

lambda-http/src/deserializer.rs

@@ -1,8 +1,4 @@
 use crate::request::LambdaRequest;
-use aws_lambda_events::{
-    alb::AlbTargetGroupRequest,
-    apigw::{ApiGatewayProxyRequest, ApiGatewayV2httpRequest, ApiGatewayWebsocketProxyRequest},
-};
 use serde::{de::Error, Deserialize};
 
 const ERROR_CONTEXT: &str = "this function expects a JSON payload from Amazon API Gateway, Amazon Elastic Load Balancer, or AWS Lambda Function URLs, but the data doesn't match any of those services' events";
@@ -17,28 +13,29 @@ impl<'de> Deserialize<'de> for LambdaRequest {
             Err(err) => return Err(err),
         };
         #[cfg(feature = "apigw_rest")]
-        if let Ok(res) =
-            ApiGatewayProxyRequest::deserialize(serde::__private::de::ContentRefDeserializer::<D::Error>::new(&content))
-        {
+        if let Ok(res) = aws_lambda_events::apigw::ApiGatewayProxyRequest::deserialize(
+            serde::__private::de::ContentRefDeserializer::<D::Error>::new(&content),
+        ) {
             return Ok(LambdaRequest::ApiGatewayV1(res));
         }
         #[cfg(feature = "apigw_http")]
-        if let Ok(res) = ApiGatewayV2httpRequest::deserialize(
+        if let Ok(res) = aws_lambda_events::apigw::ApiGatewayV2httpRequest::deserialize(
             serde::__private::de::ContentRefDeserializer::<D::Error>::new(&content),
         ) {
             return Ok(LambdaRequest::ApiGatewayV2(res));
         }
         #[cfg(feature = "alb")]
         if let Ok(res) =
-            AlbTargetGroupRequest::deserialize(serde::__private::de::ContentRefDeserializer::<D::Error>::new(&content))
+            aws_lambda_events::alb::AlbTargetGroupRequest::deserialize(serde::__private::de::ContentRefDeserializer::<
+                D::Error,
+            >::new(&content))
         {
             return Ok(LambdaRequest::Alb(res));
         }
         #[cfg(feature = "apigw_websockets")]
-        if let Ok(res) = ApiGatewayWebsocketProxyRequest::deserialize(serde::__private::de::ContentRefDeserializer::<
-            D::Error,
-        >::new(&content))
-        {
+        if let Ok(res) = aws_lambda_events::apigw::ApiGatewayWebsocketProxyRequest::deserialize(
+            serde::__private::de::ContentRefDeserializer::<D::Error>::new(&content),
+        ) {
             return Ok(LambdaRequest::WebSocket(res));
         }
 

lambda-http/src/request.rs

@@ -8,6 +8,12 @@
 //! [`RequestExt`]: crate::RequestExt
 #[cfg(any(feature = "apigw_rest", feature = "apigw_http", feature = "apigw_websockets"))]
 use crate::ext::extensions::{PathParameters, StageVariables};
+#[cfg(any(
+    feature = "apigw_rest",
+    feature = "apigw_http",
+    feature = "alb",
+    feature = "apigw_websockets"
+))]
 use crate::ext::extensions::{QueryStringParameters, RawHttpPath};
 #[cfg(feature = "alb")]
 use aws_lambda_events::alb::{AlbTargetGroupRequest, AlbTargetGroupRequestContext};
@@ -26,7 +32,7 @@ use serde_json::error::Error as JsonError;
 
 use std::future::Future;
 use std::pin::Pin;
-use std::{env, io::Read, mem};
+use std::{env, io::Read};
 use url::Url;
 
 /// Internal representation of an Lambda http event from
@@ -61,6 +67,13 @@ impl LambdaRequest {
             LambdaRequest::Alb { .. } => RequestOrigin::Alb,
             #[cfg(feature = "apigw_websockets")]
             LambdaRequest::WebSocket { .. } => RequestOrigin::WebSocket,
+            #[cfg(not(any(
+                feature = "apigw_rest",
+                feature = "apigw_http",
+                feature = "alb",
+                feature = "apigw_websockets"
+            )))]
+            _ => compile_error!("Either feature `apigw_rest`, `apigw_http`, `alb`, or `apigw_websockets` must be enabled for the `lambda-http` crate."),
         }
     }
 }
@@ -141,8 +154,8 @@ fn into_api_gateway_v2_request(ag: ApiGatewayV2httpRequest) -> http::Request<Bod
         .expect("failed to build request");
 
     // no builder method that sets headers in batch
-    let _ = mem::replace(req.headers_mut(), headers);
-    let _ = mem::replace(req.method_mut(), http_method);
+    let _ = std::mem::replace(req.headers_mut(), headers);
+    let _ = std::mem::replace(req.method_mut(), http_method);
 
     req
 }

lambda-http/src/response.rs

@@ -114,6 +114,13 @@ impl LambdaResponse {
                 headers: headers.clone(),
                 multi_value_headers: headers,
             }),
+            #[cfg(not(any(
+                feature = "apigw_rest",
+                feature = "apigw_http",
+                feature = "alb",
+                feature = "apigw_websockets"
+            )))]
+            _ => compile_error!("Either feature `apigw_rest`, `apigw_http`, `alb`, or `apigw_websockets` must be enabled for the `lambda-http` crate."),
         }
     }
 }