Command: redirect stdout/stderr to sys.stdout/stderr

Redirect stdout and stderr of the (child) command to sys.stdout and
sys.stderr of the caller, respectively. This change is mainly for the
unit tests. It makes Python nose to correctly capture the output of the
child command, too, which in turn suppresses a lot of spurious output
when running nosetests.

Closes: #829690

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>

1 files changed, 49 insertions, 16 deletions

diff --git a/gbp/command_wrappers.py b/gbp/command_wrappers.py
index f99b1e85..e16c1080 100644
--- a/gbp/command_wrappers.py
+++ b/gbp/command_wrappers.py
@@ -22,6 +22,10 @@ git-buildpackage and friends
 import subprocess
 import os
 import signal
+import sys
+from contextlib import contextmanager
+from tempfile import TemporaryFile
+
 import gbp.log as log
 
 
@@ -30,6 +34,35 @@ class CommandExecFailed(Exception):
     pass
 
 
+@contextmanager
+def proxy_stdf():
+    """
+    Circulate stdout/stderr via a proper file object. Designed to work around a
+    problem where Python nose replaces sys.stdout/stderr with a custom 'Tee'
+    object that is not a file object (compatible) and thus causes a crash with
+    Popen.
+    """
+    stdout = None
+    if not hasattr(sys.stdout, 'fileno'):
+        stdout = sys.stdout
+        sys.stdout = TemporaryFile()
+    stderr = None
+    if not hasattr(sys.stderr, 'fileno'):
+        stderr = sys.stderr
+        sys.stderr = TemporaryFile()
+    try:
+        yield
+    finally:
+        if stdout:
+            sys.stdout.seek(0)
+            stdout.write(sys.stdout.read())
+            sys.stdout = stdout
+        if stderr:
+            sys.stderr.seek(0)
+            stderr.write(sys.stderr.read())
+            sys.stderr = stderr
+
+
 class Command(object):
     """
     Wraps a shell command, so we don't have to store any kind of command
@@ -67,26 +100,26 @@ class Command(object):
 
         log.debug("%s %s %s" % (self.cmd, self.args, args))
         self._reset_state()
-        stdout_arg = subprocess.PIPE if self.capture_stdout else None
-        stderr_arg = subprocess.PIPE if self.capture_stderr else None
         cmd = [self.cmd] + self.args + args
         if self.shell:
             # subprocess.call only cares about the first argument if shell=True
             cmd = " ".join(cmd)
-
-        try:
-            popen = subprocess.Popen(cmd,
-                                     cwd=self.cwd,
-                                     shell=self.shell,
-                                     env=self.env,
-                                     preexec_fn=default_sigpipe,
-                                     stdout=stdout_arg,
-                                     stderr=stderr_arg)
-            (self.stdout, self.stderr) = popen.communicate()
-        except OSError as err:
-            self.err_reason = "execution failed: %s" % str(err)
-            self.retcode = 1
-            raise
+        with proxy_stdf():
+            stdout_arg = subprocess.PIPE if self.capture_stdout else sys.stdout
+            stderr_arg = subprocess.PIPE if self.capture_stderr else sys.stderr
+            try:
+                popen = subprocess.Popen(cmd,
+                                         cwd=self.cwd,
+                                         shell=self.shell,
+                                         env=self.env,
+                                         preexec_fn=default_sigpipe,
+                                         stdout=stdout_arg,
+                                         stderr=stderr_arg)
+                (self.stdout, self.stderr) = popen.communicate()
+            except OSError as err:
+                self.err_reason = "execution failed: %s" % str(err)
+                self.retcode = 1
+                raise
 
         self.retcode = popen.returncode
         if self.retcode < 0: