api-client: Allow response to be captured

Previously, the API response was always written to stdout, but that may
not be appropriate for all clients.

The client can now control this behaviour as the client API returns the
response in the `Result`.

Fixes: #4703.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

api_client/src/lib.rs

@@ -143,13 +143,13 @@ fn parse_http_response(socket: &mut dyn Read) -> Result<Option<String>, Error> {
 
 /// Make an API request using the fully qualified command name.
 /// For example, full_command could be "vm.create" or "vmm.ping".
-pub fn simple_api_full_command_with_fds<T: Read + Write + ScmSocket>(
+pub fn simple_api_full_command_with_fds_and_response<T: Read + Write + ScmSocket>(
     socket: &mut T,
     method: &str,
     full_command: &str,
     request_body: Option<&str>,
     request_fds: Vec<RawFd>,
-) -> Result<(), Error> {
+) -> Result<Option<String>, Error> {
     socket
         .send_with_fds(
             &[format!(
@@ -177,9 +177,28 @@ pub fn simple_api_full_command_with_fds<T: Read + Write + ScmSocket>(
 
     socket.flush().map_err(Error::Socket)?;
 
-    if let Some(body) = parse_http_response(socket)? {
-        println!("{}", body);
+    parse_http_response(socket)
+}
+
+pub fn simple_api_full_command_with_fds<T: Read + Write + ScmSocket>(
+    socket: &mut T,
+    method: &str,
+    full_command: &str,
+    request_body: Option<&str>,
+    request_fds: Vec<RawFd>,
+) -> Result<(), Error> {
+    let response = simple_api_full_command_with_fds_and_response(
+        socket,
+        method,
+        full_command,
+        request_body,
+        request_fds,
+    )?;
+
+    if response.is_some() {
+        println!("{}", response.unwrap());
     }
+
     Ok(())
 }
 
@@ -192,6 +211,21 @@ pub fn simple_api_full_command<T: Read + Write + ScmSocket>(
     simple_api_full_command_with_fds(socket, method, full_command, request_body, Vec::new())
 }
 
+pub fn simple_api_full_command_and_response<T: Read + Write + ScmSocket>(
+    socket: &mut T,
+    method: &str,
+    full_command: &str,
+    request_body: Option<&str>,
+) -> Result<Option<String>, Error> {
+    simple_api_full_command_with_fds_and_response(
+        socket,
+        method,
+        full_command,
+        request_body,
+        Vec::new(),
+    )
+}
+
 pub fn simple_api_command_with_fds<T: Read + Write + ScmSocket>(
     socket: &mut T,
     method: &str,