iotests: Factor out qemu_tool_pipe_and_status()

We have three almost identical functions that call an external process
and return its output and return code. Refactor them into small wrappers
around a common function.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200924152717.287415-29-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/iotests.py

@@ -88,21 +88,30 @@
 luks_default_key_secret_opt = 'key-secret=keysec0'
 
 
-def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
+def qemu_tool_pipe_and_status(tool: str, args: Sequence[str],
+                              connect_stderr: bool = True) -> Tuple[str, int]:
     """
-    Run qemu-img and return both its output and its exit code
+    Run a tool and return both its output and its exit code
     """
-    subp = subprocess.Popen(qemu_img_args + list(args),
+    stderr = subprocess.STDOUT if connect_stderr else None
+    subp = subprocess.Popen(args,
                             stdout=subprocess.PIPE,
-                            stderr=subprocess.STDOUT,
+                            stderr=stderr,
                             universal_newlines=True)
     output = subp.communicate()[0]
     if subp.returncode < 0:
-        sys.stderr.write('qemu-img received signal %i: %s\n'
-                         % (-subp.returncode,
+        sys.stderr.write('%s received signal %i: %s\n'
+                         % (tool, -subp.returncode,
                             ' '.join(qemu_img_args + list(args))))
     return (output, subp.returncode)
 
+def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
+    """
+    Run qemu-img and return both its output and its exit code
+    """
+    full_args = qemu_img_args + list(args)
+    return qemu_tool_pipe_and_status('qemu-img', full_args)
+
 def qemu_img(*args: str) -> int:
     '''Run qemu-img and return the exit code'''
     return qemu_img_pipe_and_status(*args)[1]
@@ -263,19 +272,13 @@ def qemu_nbd(*args):
     '''Run qemu-nbd in daemon mode and return the parent's exit code'''
     return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))
 
-def qemu_nbd_early_pipe(*args):
+def qemu_nbd_early_pipe(*args: str) -> Tuple[int, str]:
     '''Run qemu-nbd in daemon mode and return both the parent's exit code
        and its output in case of an error'''
-    subp = subprocess.Popen(qemu_nbd_args + ['--fork'] + list(args),
-                            stdout=subprocess.PIPE,
-                            universal_newlines=True)
-    output = subp.communicate()[0]
-    if subp.returncode < 0:
-        sys.stderr.write('qemu-nbd received signal %i: %s\n' %
-                         (-subp.returncode,
-                          ' '.join(qemu_nbd_args + ['--fork'] + list(args))))
-
-    return subp.returncode, output if subp.returncode else ''
+    full_args = qemu_nbd_args + ['--fork'] + list(args)
+    output, returncode = qemu_tool_pipe_and_status('qemu-nbd', full_args,
+                                                   connect_stderr=False)
+    return returncode, output if returncode else ''
 
 @contextmanager
 def qemu_nbd_popen(*args):
@@ -1141,20 +1144,14 @@ def verify_working_luks():
     if not working:
         notrun(reason)
 
-def qemu_pipe(*args):
+def qemu_pipe(*args: str) -> str:
     """
     Run qemu with an option to print something and exit (e.g. a help option).
 
     :return: QEMU's stdout output.
     """
-    args = [qemu_prog] + qemu_opts + list(args)
-    subp = subprocess.Popen(args, stdout=subprocess.PIPE,
-                            stderr=subprocess.STDOUT,
-                            universal_newlines=True)
-    output = subp.communicate()[0]
-    if subp.returncode < 0:
-        sys.stderr.write('qemu received signal %i: %s\n' %
-                         (-subp.returncode, ' '.join(args)))
+    full_args = [qemu_prog] + qemu_opts + list(args)
+    output, _ = qemu_tool_pipe_and_status('qemu', full_args)
     return output
 
 def supported_formats(read_only=False):