Return true for Body::is_empty for HEAD responses (#343)

Fixes #341.

src/client.rs

@@ -1166,6 +1166,8 @@ impl crate::interceptor::Invoke for &HttpClient {
  mut request: Request<AsyncBody>,
  ) -> crate::interceptor::InterceptorFuture<'_, Error> {
  Box::pin(async move {
+ let is_head_request = request.method() == http::Method::HEAD;
+
  // Set default user agent if not specified.
  request
  .headers_mut()
@@ -1212,17 +1214,21 @@ impl crate::interceptor::Invoke for &HttpClient {
 
  // Convert the reader into an opaque Body.
  Ok(response.map(|reader| {
- let body = ResponseBody {
- inner: reader,
- // Extend the lifetime of the agent by including a reference
- // to its handle in the response body.
- _client: (*self).clone(),
- };
-
- if let Some(len) = body_len {
- AsyncBody::from_reader_sized(body, len)
+ if is_head_request {
+ AsyncBody::empty()
  } else {
- AsyncBody::from_reader(body)
+ let body = ResponseBody {
+ inner: reader,
+ // Extend the lifetime of the agent by including a reference
+ // to its handle in the response body.
+ _client: (*self).clone(),
+ };
+
+ if let Some(len) = body_len {
+ AsyncBody::from_reader_sized(body, len)
+ } else {
+ AsyncBody::from_reader(body)
+ }
  }
  }))
  })

tests/response_body.rs

@@ -18,6 +18,18 @@ fn simple_response_body() {
  assert_eq!(response_text, "hello world");
 }
 
+#[test]
+fn zero_length_response_body() {
+ let m = mock! {
+ body: "",
+ };
+
+ let response = isahc::get(m.url()).unwrap();
+
+ assert_eq!(response.body().len(), Some(0));
+ assert!(!response.body().is_empty());
+}
+
 #[test]
 fn large_response_body() {
  let body = "wow so large ".repeat(1000);
@@ -58,6 +70,20 @@ fn response_body_with_chunked_encoding_has_unknown_size() {
  assert_eq!(response.body().len(), None);
 }
 
+// See issue #341.
+#[test]
+fn head_request_with_content_length_response_returns_empty_body() {
+ let m = mock! {
+ headers {
+ "content-length": 767,
+ }
+ };
+
+ let response = isahc::head(m.url()).unwrap();
+
+ assert!(response.body().is_empty());
+}
+
 // See issue #64.
 #[test]
 fn dropping_client_does_not_abort_response_transfer() {