Add Cleaner executor

README.md

@@ -88,8 +88,9 @@ Configuration
 -------------
 
 Dotbot uses json-formatted configuration files to let you specify how to set up
-your dotfiles. Currently, Dotbot knows how to `link` files and execute `shell`
-commands. Dotbot executes tasks in the order that they are specified in.
+your dotfiles. Currently, Dotbot knows how to `link` files, execute `shell`
+commands, and `clean` directories of broken symbolic links. Dotbot executes
+tasks in the order that they are specified in.
 
 **Ideally, bootstrap configurations should be idempotent. That is, the
 installer should be able to be run multiple times without causing any
@@ -100,7 +101,8 @@ dictionary that contains a command name mapping to data for that command. For
 `link`, you specify how files should be linked in a dictionary. For `shell`,
 you specify an array consisting of commands, where each command is an array
 consisting of the shell command as the first element and a description as the
-second.
+second. For `clean`, you specify an array consisting of targets, where each
+target is a path to a directory.
 
 Dotbot is aware of a base directory (that is specified when running the
 installer), so link targets can be specified relative to that, and shell
@@ -111,6 +113,9 @@ started. The convention for configuration file names is `install.conf.json`.
 
 ```json
 [
+    {
+        "clean": ["~"]
+    },
     {
         "link": {
             "~/.tmux.conf": "tmux.conf",

dotbot/executor/__init__.py

@@ -1,3 +1,4 @@
 from .executor import Executor
 from .linker import Linker
+from .cleaner import Cleaner
 from .commandrunner import CommandRunner

dotbot/executor/cleaner.py

@@ -0,0 +1,49 @@
+import os
+from . import Executor
+
+class Cleaner(Executor):
+    '''
+    Cleans broken symbolic links.
+    '''
+
+    _directive = 'clean'
+
+    def can_handle(self, directive):
+        return directive == self._directive
+
+    def handle(self, directive, data):
+        if directive != self._directive:
+            raise ValueError('Cleaner cannot handle directive %s' % directive)
+        return self._process_clean(data)
+
+    def _process_clean(self, targets):
+        success = True
+        for target in targets:
+            success &= self._clean(target)
+        if success:
+            self._log.info('All targets have been cleaned')
+        else:
+            self._log.error('Some targets were not succesfully cleaned')
+        return success
+
+    def _clean(self, target):
+        '''
+        Cleans all the broken symbolic links in target that point to
+        a subdirectory of the base directory.
+        '''
+        for item in os.listdir(os.path.expanduser(target)):
+            path = os.path.join(os.path.expanduser(target), item)
+            if not os.path.exists(path) and os.path.islink(path):
+                if self._in_directory(path, self._base_directory):
+                    self._log.lowinfo('Removing invalid link %s -> %s' %
+                        (path, os.path.join(os.path.dirname(path), os.readlink(path))))
+                    os.remove(path)
+        return True
+
+    def _in_directory(self, path, directory):
+        '''
+        Returns true if the path is in the directory.
+        '''
+        directory = os.path.join(os.path.realpath(directory), '')
+        path = os.path.realpath(path)
+        return os.path.commonprefix([path, directory]) == directory