util.command_output: return stderr, too

Return a namedtuple CommandOutput(stdout, stderr) instead of just stdout from
util.command_ouput, allowing separate access to stdout and stderr.

This change is required by the ffmpeg replaygain backend (GitHub
PullRequest #3056) as ffmpeg's ebur128 filter outputs only to stderr.

beets/util/__init__.py

@@ -24,7 +24,7 @@ import re
 import shutil
 import fnmatch
 import functools
-from collections import Counter
+from collections import Counter, namedtuple
 from multiprocessing.pool import ThreadPool
 import traceback
 import subprocess
@@ -763,7 +763,11 @@ def cpu_count():
             num = 0
     elif sys.platform == 'darwin':
         try:
-            num = int(command_output(['/usr/sbin/sysctl', '-n', 'hw.ncpu']))
+            num = int(command_output([
+                '/usr/sbin/sysctl',
+                '-n',
+                'hw.ncpu',
+                ]).stdout)
         except (ValueError, OSError, subprocess.CalledProcessError):
             num = 0
     else:
@@ -794,9 +798,15 @@ def convert_command_args(args):
     return [convert(a) for a in args]
 
 
+# stdout and stderr as bytes
+CommandOutput = namedtuple("CommandOutput", ("stdout", "stderr"))
+
+
 def command_output(cmd, shell=False):
     """Runs the command and returns its output after it has exited.
 
+    Returns a CommandOutput.
+
     ``cmd`` is a list of arguments starting with the command names. The
     arguments are bytes on Unix and strings on Windows.
     If ``shell`` is true, ``cmd`` is assumed to be a string and passed to a
@@ -831,7 +841,7 @@ def command_output(cmd, shell=False):
             cmd=' '.join(cmd),
             output=stdout + stderr,
         )
-    return stdout
+    return CommandOutput(stdout, stderr)
 
 
 def max_filename_length(path, limit=MAX_FILENAME_LENGTH):

beets/util/artresizer.py

@@ -129,7 +129,7 @@ def im_getsize(path_in):
         ['-format', '%w %h', util.syspath(path_in, prefix=False)]
 
     try:
-        out = util.command_output(cmd)
+        out = util.command_output(cmd).stdout
     except subprocess.CalledProcessError as exc:
         log.warning(u'ImageMagick size query failed')
         log.debug(
@@ -265,7 +265,7 @@ def get_im_version():
         cmd = cmd_name + ['--version']
 
         try:
-            out = util.command_output(cmd)
+            out = util.command_output(cmd).stdout
         except (subprocess.CalledProcessError, OSError) as exc:
             log.debug(u'ImageMagick version check failed: {}', exc)
         else:

beetsplug/absubmit.py

@@ -46,7 +46,7 @@ def call(args):
     Raise a AnalysisABSubmitError on failure.
     """
     try:
-        return util.command_output(args)
+        return util.command_output(args).stdout
     except subprocess.CalledProcessError as e:
         raise ABSubmitError(
             u'{0} exited with status {1}'.format(args[0], e.returncode)

beetsplug/duplicates.py

@@ -205,7 +205,7 @@ class DuplicatesPlugin(BeetsPlugin):
                             u'computing checksum',
                             key, displayable_path(item.path))
             try:
-                checksum = command_output(args)
+                checksum = command_output(args).stdout
                 setattr(item, key, checksum)
                 item.store()
                 self._log.debug(u'computed checksum for {0} using {1}',

beetsplug/ipfs.py

@@ -123,7 +123,7 @@ class IPFSPlugin(BeetsPlugin):
             cmd = "ipfs add -q -r".split()
         cmd.append(album_dir)
         try:
-            output = util.command_output(cmd).split()
+            output = util.command_output(cmd).stdout.split()
         except (OSError, subprocess.CalledProcessError) as exc:
             self._log.error(u'Failed to add {0}, error: {1}', album_dir, exc)
             return False
@@ -183,7 +183,7 @@ class IPFSPlugin(BeetsPlugin):
                 else:
                     cmd = "ipfs add -q ".split()
                 cmd.append(tmp.name)
-                output = util.command_output(cmd)
+                output = util.command_output(cmd).stdout
             except (OSError, subprocess.CalledProcessError) as err:
                 msg = "Failed to publish library. Error: {0}".format(err)
                 self._log.error(msg)

beetsplug/keyfinder.py

@@ -60,7 +60,7 @@ class KeyFinderPlugin(BeetsPlugin):
 
             try:
                 output = util.command_output([bin, '-f',
-                                              util.syspath(item.path)])
+                                              util.syspath(item.path)]).stdout
             except (subprocess.CalledProcessError, OSError) as exc:
                 self._log.error(u'execution failed: {0}', exc)
                 continue

beetsplug/replaygain.py

@@ -47,12 +47,12 @@ class FatalGstreamerPluginReplayGainError(FatalReplayGainError):
     loading the required plugins."""
 
 
-def call(args):
+def call(args, **kwargs):
     """Execute the command and return its output or raise a
     ReplayGainError on failure.
     """
     try:
-        return command_output(args)
+        return command_output(args, **kwargs)
     except subprocess.CalledProcessError as e:
         raise ReplayGainError(
             u"{0} exited with status {1}".format(args[0], e.returncode)
@@ -206,7 +206,7 @@ class Bs1770gainBackend(Backend):
         self._log.debug(
             u'executing {0}', u' '.join(map(displayable_path, args))
         )
-        output = call(args)
+        output = call(args).stdout
 
         self._log.debug(u'analysis finished: {0}', output)
         results = self.parse_tool_output(output, path_list, is_album)
@@ -378,7 +378,7 @@ class CommandBackend(Backend):
 
         self._log.debug(u'analyzing {0} files', len(items))
         self._log.debug(u"executing {0}", " ".join(map(displayable_path, cmd)))
-        output = call(cmd)
+        output = call(cmd).stdout
         self._log.debug(u'analysis finished')
         return self.parse_tool_output(output,
                                       len(items) + (1 if is_album else 0))

test/test_keyfinder.py

@@ -38,7 +38,7 @@ class KeyFinderTest(unittest.TestCase, TestHelper):
         item = Item(path='/file')
         item.add(self.lib)
 
-        command_output.return_value = 'dbm'
+        command_output.return_value = util.CommandOutput(b"dbm", b"")
         self.run_command('keyfinder')
 
         item.load()
@@ -47,7 +47,7 @@ class KeyFinderTest(unittest.TestCase, TestHelper):
             ['KeyFinder', '-f', util.syspath(item.path)])
 
     def test_add_key_on_import(self, command_output):
-        command_output.return_value = 'dbm'
+        command_output.return_value = util.CommandOutput(b"dbm", b"")
         importer = self.create_importer()
         importer.run()
 
@@ -60,7 +60,7 @@ class KeyFinderTest(unittest.TestCase, TestHelper):
         item = Item(path='/file', initial_key='F')
         item.add(self.lib)
 
-        command_output.return_value = 'C#m'
+        command_output.return_value = util.CommandOutput(b"C#m", b"")
         self.run_command('keyfinder')
 
         item.load()
@@ -70,7 +70,7 @@ class KeyFinderTest(unittest.TestCase, TestHelper):
         item = Item(path='/file', initial_key='F')
         item.add(self.lib)
 
-        command_output.return_value = 'dbm'
+        command_output.return_value = util.CommandOutput(b"dbm", b"")
         self.run_command('keyfinder')
 
         item.load()

test/test_replaygain.py

@@ -23,6 +23,7 @@ from mock import patch
 from test.helper import TestHelper, capture_log, has_program
 
 from beets import config
+from beets.util import CommandOutput
 from mediafile import MediaFile
 from beetsplug.replaygain import (FatalGstreamerPluginReplayGainError,
                                   GStreamerBackend)
@@ -169,7 +170,6 @@ class ReplayGainLdnsCliTest(ReplayGainCliTestBase, unittest.TestCase):
 
 
 class ReplayGainLdnsCliMalformedTest(TestHelper, unittest.TestCase):
-
     @patch('beetsplug.replaygain.call')
     def setUp(self, call_patch):
         self.setup_beets()
@@ -186,14 +186,14 @@ class ReplayGainLdnsCliMalformedTest(TestHelper, unittest.TestCase):
     @patch('beetsplug.replaygain.call')
     def test_malformed_output(self, call_patch):
         # Return malformed XML (the ampersand should be &)
-        call_patch.return_value = """
+        call_patch.return_value = CommandOutput(stdout="""
             <album>
                 <track total="1" number="1" file="&">
                     <integrated lufs="0" lu="0" />
                     <sample-peak spfs="0" factor="0" />
                 </track>
             </album>
-        """
+        """, stderr="")
 
         with capture_log('beets.replaygain') as logs:
             self.run_command('replaygain')