Implement --pretend option for the move command

The method `show_path_changes` takes a list of tuples (source, destination)
that will be printed on either single / double line, as proposed in #1405.

beets/ui/__init__.py

@@ -615,6 +615,44 @@ def show_model_changes(new, old=None, fields=None, always=False):
     return bool(changes)
 
 
+def show_path_changes(path_changes):
+    """ Given a list of tuples (source, destination) that indicate the path
+    changes, the changes are shown. Output is guaranteed to be unicode.
+
+    Every tuple is shown on a single line if the terminal width permits it,
+    else it is split over two lines. E.g.,
+
+    Source -> Destination
+
+    vs.
+
+    Source
+      -> Destination
+    """
+    sources, destinations = zip(*path_changes)
+
+    # Ensure unicode output
+    sources = map(util.displayable_path, sources)
+    destinations = map(util.displayable_path, destinations)
+
+    # Calculate widths for terminal split
+    col_width = (term_width() - len(' -> ')) // 2
+    max_width = len(max(sources + destinations, key=len))
+
+    if max_width > col_width:
+        # Print every change over two lines
+        for source, dest in zip(sources, destinations):
+            log.info(u'{0} \n  -> {1}', source, dest)
+    else:
+        # Print every change on a single line, and add a header
+        title_pad = max_width - len('Source ') + len(' -> ')
+
+        log.info(u'Source {0} Destination', ' ' * title_pad)
+        for source, dest in zip(sources, destinations):
+            pad = max_width - len(source)
+            log.info(u'{0} {1} -> {2}', source, ' ' * pad, dest)
+
+
 class CommonOptionsParser(optparse.OptionParser, object):
     """Offers a simple way to add common formatting options.
 

beets/ui/commands.py

@@ -24,7 +24,7 @@ import re
 
 import beets
 from beets import ui
-from beets.ui import print_, input_, decargs
+from beets.ui import print_, input_, decargs, show_path_changes
 from beets import autotag
 from beets.autotag import Recommendation
 from beets.autotag import hooks
@@ -1344,7 +1344,7 @@ default_commands.append(modify_cmd)
 
 # move: Move/copy files to the library or a new base directory.
 
-def move_items(lib, dest, query, copy, album):
+def move_items(lib, dest, query, copy, album, pretend):
     """Moves or copies items to a new base directory, given by dest. If
     dest is None, then the library's base directory is used, making the
     command "consolidate" files.
@@ -1355,11 +1355,19 @@ def move_items(lib, dest, query, copy, album):
     action = 'Copying' if copy else 'Moving'
     entity = 'album' if album else 'item'
     log.info(u'{0} {1} {2}s.', action, len(objs), entity)
-    for obj in objs:
-        log.debug(u'moving: {0}', util.displayable_path(obj.path))
+    if pretend:
+        if album:
+            show_path_changes([(item.path, item.destination(basedir=dest))
+                               for obj in objs for item in obj.items()])
+        else:
+            show_path_changes([(obj.path, obj.destination(basedir=dest))
+                               for obj in objs])
+    else:
+        for obj in objs:
+            log.debug(u'moving: {0}', util.displayable_path(obj.path))
 
-        obj.move(copy, basedir=dest)
-        obj.store()
+            obj.move(copy, basedir=dest)
+            obj.store()
 
 
 def move_func(lib, opts, args):
@@ -1369,7 +1377,7 @@ def move_func(lib, opts, args):
         if not os.path.isdir(dest):
             raise ui.UserError('no such directory: %s' % dest)
 
-    move_items(lib, dest, decargs(args), opts.copy, opts.album)
+    move_items(lib, dest, decargs(args), opts.copy, opts.album, opts.pretend)
 
 
 move_cmd = ui.Subcommand(
@@ -1383,6 +1391,9 @@ move_cmd.parser.add_option(
     '-c', '--copy', default=False, action='store_true',
     help='copy instead of moving'
 )
+move_cmd.parser.add_option(
+    '-p', '--pretend', default=False, action='store_true',
+    help='show how files would be moved, but don\'t touch anything')
 move_cmd.parser.add_album_option()
 move_cmd.func = move_func
 default_commands.append(move_cmd)

docs/changelog.rst

@@ -13,6 +13,8 @@ New features:
   This plugin is still in an experimental phase. :bug:`1450`
 * The :doc:`/plugins/fetchart` plugin will now complain for the `enforce_ratio`
   and `min_width` options if no local imaging backend is available. :bug:`1460`
+* The `move` command has a new `-p/--pretend` option, making the command show
+  how the items will be moved, without modifying the files on disk.
 
 
 Fixes:

docs/reference/cli.rst

@@ -245,7 +245,7 @@ move
 ````
 ::
 
-    beet move [-ca] [-d DIR] QUERY
+    beet move [-cap] [-d DIR] QUERY
 
 Move or copy items in your library.
 
@@ -255,6 +255,10 @@ destination directory with ``-d`` manually, you can move items matching a query
 anywhere in your filesystem. The ``-c`` option copies files instead of moving
 them. As with other commands, the ``-a`` option matches albums instead of items.
 
+To perform a "dry run", just use the ``-p`` (for "pretend") flag. This will
+show you all how the files would be moved but won't actually change anything
+on disk.
+
 .. _update-cmd:
 
 update

test/test_ui.py

@@ -373,8 +373,9 @@ class MoveTest(_common.TestCase):
         # Alternate destination directory.
         self.otherdir = os.path.join(self.temp_dir, 'testotherdir')
 
-    def _move(self, query=(), dest=None, copy=False, album=False):
-        commands.move_items(self.lib, dest, query, copy, album)
+    def _move(self, query=(), dest=None, copy=False, album=False,
+              pretend=False):
+        commands.move_items(self.lib, dest, query, copy, album, pretend)
 
     def test_move_item(self):
         self._move()
@@ -418,6 +419,16 @@ class MoveTest(_common.TestCase):
         self.assertExists(self.i.path)
         self.assertNotExists(self.itempath)
 
+    def test_pretend_move_item(self):
+        self._move(dest=self.otherdir, pretend=True)
+        self.i.load()
+        self.assertIn('srcfile', self.i.path)
+
+    def test_pretend_move_album(self):
+        self._move(album=True, pretend=True)
+        self.i.load()
+        self.assertIn('srcfile', self.i.path)
+
 
 class UpdateTest(_common.TestCase):
     def setUp(self):