Allow `Image::pull` to handle chunks with multiple JSON values (#240)

* add fn for stream post that returns json values

use when pulling docker images, to fix bug where
shiplift would error if multiple JSON values were
returned in a single HTTP chunk

* fix unnecessary lazy evaluation

* add comments to stream post requests

2 files changed, 33 insertions, 26 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 7d62523..f44919a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -164,25 +164,12 @@ impl<'a> Images<'a> {
 
                 tarball::dir(&mut bytes, &opts.path[..])?;
 
-                let chunk_stream = self.docker.stream_post(
+                let value_stream = self.docker.stream_post_into_values(
                     path.join("?"),
                     Some((Body::from(bytes), tar())),
                     None::<iter::Empty<_>>,
                 );
 
-                let value_stream = chunk_stream
-                    .and_then(|chunk| async move {
-                        let stream = futures_util::stream::iter(
-                            serde_json::Deserializer::from_slice(&chunk)
-                                .into_iter()
-                                .collect::<Vec<_>>(),
-                        )
-                        .map_err(Error::from);
-
-                        Ok(stream)
-                    })
-                    .try_flatten();
-
                 Ok(value_stream)
             }
             .try_flatten_stream(),
@@ -237,11 +224,7 @@ impl<'a> Images<'a> {
 
         Box::pin(
             self.docker
-                .stream_post(path.join("?"), None, headers)
-                .and_then(move |chunk| {
-                    // todo: give this a proper enum type
-                    futures_util::future::ready(serde_json::from_slice(&chunk).map_err(Error::from))
-                }),
+                .stream_post_into_values(path.join("?"), None, headers),
         )
     }
 
@@ -272,16 +255,11 @@ impl<'a> Images<'a> {
 
                 tarball.read_to_end(&mut bytes)?;
 
-                let chunk_stream = self.docker.stream_post(
+                let value_stream = self.docker.stream_post_into_values(
                     "/images/load",
                     Some((Body::from(bytes), tar())),
                     None::<iter::Empty<_>>,
                 );
-
-                let value_stream = chunk_stream.and_then(|chunk| async move {
-                    serde_json::from_slice(&chunk).map_err(Error::from)
-                });
-
                 Ok(value_stream)
             }
             .try_flatten_stream(),
@@ -1165,6 +1143,9 @@ impl Docker {
         Ok(serde_json::from_str::<T>(&string)?)
     }
 
+    /// Send a streaming post request.
+    ///
+    /// Use stream_post_into_values if the endpoint returns JSON values
     fn stream_post<'a, H>(
         &'a self,
         endpoint: impl AsRef<str> + 'a,
@@ -1178,6 +1159,32 @@ impl Docker {
             .stream_chunks(Method::POST, endpoint, body, headers)
     }
 
+    /// Send a streaming post request that returns a stream of JSON values
+    ///
+    /// Assumes that each received chunk contains one or more JSON values
+    fn stream_post_into_values<'a, H>(
+        &'a self,
+        endpoint: impl AsRef<str> + 'a,
+        body: Option<(Body, Mime)>,
+        headers: Option<H>,
+    ) -> impl Stream<Item = Result<Value>> + 'a
+    where
+        H: IntoIterator<Item = (&'static str, String)> + 'a,
+    {
+        self.stream_post(endpoint, body, headers)
+            .and_then(|chunk| async move {
+                let stream = futures_util::stream::iter(
+                    serde_json::Deserializer::from_slice(&chunk)
+                        .into_iter()
+                        .collect::<Vec<_>>(),
+                )
+                .map_err(Error::from);
+
+                Ok(stream)
+            })
+            .try_flatten()
+    }
+
     fn stream_get<'a>(
         &'a self,
         endpoint: impl AsRef<str> + Unpin + 'a,
diff --git a/src/transport.rs b/src/transport.rs
index 5a48f62..3ad3b9e 100644
--- a/src/transport.rs
+++ b/src/transport.rs
@@ -122,7 +122,7 @@ impl Transport {
                     message: Self::get_error_message(&message_body).unwrap_or_else(|| {
                         status
                             .canonical_reason()
-                            .unwrap_or_else(|| "unknown error code")
+                            .unwrap_or("unknown error code")
                             .to_owned()
                     }),
                 })