Add a dry run mode.

7 files changed, 98 insertions, 47 deletions

diff --git a/dotbot/cli.py b/dotbot/cli.py
index 0795d40..b09461e 100644
--- a/dotbot/cli.py
+++ b/dotbot/cli.py
@@ -18,6 +18,8 @@ def add_options(parser):
         help='suppress most output')
     parser.add_argument('-v', '--verbose', action='store_true',
         help='enable verbose output')
+    parser.add_argument('-n', '--dry-run', action='store_true',
+        help='do not actually perform any changes')
     parser.add_argument('-d', '--base-directory',
         help='execute commands from within BASEDIR',
         metavar='BASEDIR')
@@ -97,7 +99,8 @@ def main():
             # default to directory of config file
             base_directory = os.path.dirname(os.path.abspath(options.config_file))
         os.chdir(base_directory)
-        dispatcher = Dispatcher(base_directory, only=options.only, skip=options.skip)
+        dispatcher = Dispatcher(base_directory, only=options.only, skip=options.skip,
+                                dry_run = options.dry_run)
         success = dispatcher.dispatch(tasks)
         if success:
             log.verbose('\n==> All tasks executed successfully')
diff --git a/dotbot/dispatcher.py b/dotbot/dispatcher.py
index f809bef..9c55050 100644
--- a/dotbot/dispatcher.py
+++ b/dotbot/dispatcher.py
@@ -4,12 +4,13 @@ from .messenger import Messenger
 from .context import Context
 
 class Dispatcher(object):
-    def __init__(self, base_directory, only=None, skip=None):
+    def __init__(self, base_directory, only=None, skip=None, dry_run = False):
         self._log = Messenger()
         self._setup_context(base_directory)
         self._load_plugins()
         self._only = only
         self._skip = skip
+        self._dry_run = dry_run
 
     def _setup_context(self, base_directory):
         path = os.path.abspath(
@@ -34,7 +35,7 @@ class Dispatcher(object):
                 for plugin in self._plugins:
                     if plugin.can_handle(action):
                         try:
-                            success &= plugin.handle(action, task[action])
+                            success &= plugin.handle(action, task[action], self._dry_run)
                             handled = True
                         except Exception as err:
                             self._log.error(
diff --git a/dotbot/plugin.py b/dotbot/plugin.py
index 5e2c923..2d12636 100644
--- a/dotbot/plugin.py
+++ b/dotbot/plugin.py
@@ -18,10 +18,13 @@ class Plugin(object):
         '''
         return directive == self._directive
 
-    def handle(self, directive, data):
+    def handle(self, directive, data, dry_run = False):
         '''
         Executes the directive.
 
         Returns true if the Plugin successfully handled the directive.
+
+        When dry_run is True, the plugin will not perform any actions, only
+        return False when there is nothing to do, True otherwise.
         '''
         raise NotImplementedError
diff --git a/dotbot/plugins/clean.py b/dotbot/plugins/clean.py
index c8f3a03..212fb07 100644
--- a/dotbot/plugins/clean.py
+++ b/dotbot/plugins/clean.py
@@ -9,7 +9,7 @@ class Clean(dotbot.Plugin):
 
     _directive = 'clean'
 
-    def handle(self, directive, targets):
+    def handle(self, directive, targets, dry_run):
         success = True
         defaults = self._context.defaults().get(self._directive, {})
         for target in targets:
@@ -18,14 +18,22 @@ class Clean(dotbot.Plugin):
             if isinstance(targets, dict) and isinstance(targets[target], dict):
                 force = targets[target].get('force', force)
                 recursive = targets[target].get('recursive', recursive)
-            success &= self._clean(target, force, recursive)
-        if success:
-            self._log.verbose('All targets have been cleaned')
+            success &= self._clean(target, force, recurseve, dry_run)
+
+        if dry_run:
+            if success:
+                self._log.verbose('clean/dry run: nothing to do')
+            else:
+                self._log.verbose('clean/dry run: some targets are dirty')
         else:
-            self._log.error('Some targets were not successfully cleaned')
+            if success:
+                self._log.verbose('All targets have been cleaned')
+            else:
+                self._log.error('Some targets were not successfully cleaned')
+
         return success
 
-    def _clean(self, target, force, recursive):
+    def _clean(self, target, force, recursive, dry_run):
         '''
         Cleans all the broken symbolic links in target if they point to
         a subdirectory of the base directory or if forced to clean.
@@ -33,21 +41,28 @@ class Clean(dotbot.Plugin):
         if not os.path.isdir(os.path.expandvars(os.path.expanduser(target))):
             self._log.debug('Ignoring nonexistent directory %s' % target)
             return True
+
+        ret = True
         for item in os.listdir(os.path.expandvars(os.path.expanduser(target))):
             path = os.path.join(os.path.expandvars(os.path.expanduser(target)), item)
             if recursive and os.path.isdir(path):
                 # isdir implies not islink -- we don't want to descend into
                 # symlinked directories. okay to do a recursive call here
                 # because depth should be fairly limited
-                self._clean(path, force, recursive)
+                ret &= self._clean(path, force, recursive)
             if not os.path.exists(path) and os.path.islink(path):
                 points_at = os.path.join(os.path.dirname(path), os.readlink(path))
                 if self._in_directory(path, self._context.base_directory()) or force:
                     self._log.info('Removing invalid link %s -> %s' % (path, points_at))
-                    os.remove(path)
+
+                    if dry_run:
+                        ret = False
+                    else:
+                        os.remove(path)
                 else:
                     self._log.verbose('Link %s -> %s not removed.' % (path, points_at))
-        return True
+
+        return ret
 
     def _in_directory(self, path, directory):
         '''
diff --git a/dotbot/plugins/create.py b/dotbot/plugins/create.py
index 2420558..aa14277 100644
--- a/dotbot/plugins/create.py
+++ b/dotbot/plugins/create.py
@@ -9,15 +9,23 @@ class Create(dotbot.Plugin):
 
     _directive = 'create'
 
-    def handle(self, directive, paths):
+    def handle(self, directive, paths, dry_run):
         success = True
         for path in paths:
             path = os.path.expandvars(os.path.expanduser(path))
-            success &= self._create(path)
-        if success:
-            self._log.verbose('All paths have been set up')
+            success &= self._create(path, dry_run)
+
+        if dry_run:
+            if success:
+                self._log.verbose('create/dry run: nothing to do')
+            else:
+                self._log.verbose('create/dry run: some targets are missing')
         else:
-            self._log.error('Some paths were not successfully set up')
+            if success:
+                self._log.verbose('All paths have been set up')
+            else:
+                self._log.error('Some paths were not successfully set up')
+
         return success
 
     def _exists(self, path):
@@ -27,16 +35,20 @@ class Create(dotbot.Plugin):
         path = os.path.expanduser(path)
         return os.path.exists(path)
 
-    def _create(self, path):
+    def _create(self, path, dry_run):
+        if self._exists(path):
+            self._log.verbose('Path exists %s' % path)
+            return True
+
         success = True
-        if not self._exists(path):
-            self._log.debug('Trying to create path %s' % path)
+        self._log.info('Creating path %s' % path)
+        if dry_run:
+            success = False
+        else:
             try:
-                self._log.info('Creating path %s' % path)
                 os.makedirs(path)
             except OSError:
                 self._log.warning('Failed to create path %s' % path)
                 success = False
-        else:
-            self._log.verbose('Path exists %s' % path)
+
         return success
diff --git a/dotbot/plugins/link.py b/dotbot/plugins/link.py
index 411a0ef..5e2bd90 100644
--- a/dotbot/plugins/link.py
+++ b/dotbot/plugins/link.py
@@ -11,7 +11,7 @@ class Link(dotbot.Plugin):
 
     _directive = 'link'
 
-    def handle(self, directive, links):
+    def handle(self, directive, links, dry_run):
         success = True
         defaults = self._context.defaults().get('link', {})
         for destination, source in links.items():
@@ -47,12 +47,20 @@ class Link(dotbot.Plugin):
                     (destination, path))
                 continue
             if force or relink:
-                success &= self._delete(path, destination, relative, canonical_path, force)
-            success &= self._link(path, destination, relative, canonical_path, ignore_missing)
-        if success:
-            self._log.verbose('All links have been set up')
+                success &= self._delete(path, destination, relative, canonical_path, force, dry_run)
+            success &= self._link(path, destination, relative, canonical_path, ignore_missing, dry_run)
+
+        if dry_run:
+            if success:
+                self._log.verbose('link/dry run: nothing to do')
+            else:
+                self._log.verbose('link/dry run: some targets are missing')
         else:
-            self._log.error('Some links were not successfully set up')
+            if success:
+                self._log.verbose('All links have been set up')
+            else:
+                self._log.error('Some links were not successfully set up')
+
         return success
 
     def _test_success(self, command):
@@ -91,7 +99,7 @@ class Link(dotbot.Plugin):
         path = os.path.expanduser(path)
         return os.path.exists(path)
 
-    def _delete(self, source, path, relative, canonical_path, force):
+    def _delete(self, source, path, relative, canonical_path, force, dry_run):
         success = True
         source = os.path.join(self._context.base_directory(canonical_path=canonical_path), source)
         fullpath = os.path.expanduser(path)
@@ -99,7 +107,11 @@ class Link(dotbot.Plugin):
             source = self._relative_path(source, fullpath)
         if ((self._is_link(path) and self._link_destination(path) != source) or
                 (self._exists(path) and not self._is_link(path))):
-            removed = False
+            self._log.info('Removing %s' % path)
+
+            if dry_run:
+                return False
+
             try:
                 if os.path.islink(fullpath):
                     os.unlink(fullpath)
@@ -107,16 +119,12 @@ class Link(dotbot.Plugin):
                 elif force:
                     if os.path.isdir(fullpath):
                         shutil.rmtree(fullpath)
-                        removed = True
                     else:
                         os.remove(fullpath)
-                        removed = True
             except OSError:
                 self._log.warning('Failed to remove %s' % path)
                 success = False
-            else:
-                if removed:
-                    self._log.info('Removing %s' % path)
+
         return success
 
     def _relative_path(self, source, destination):
@@ -127,7 +135,7 @@ class Link(dotbot.Plugin):
         destination_dir = os.path.dirname(destination)
         return os.path.relpath(source, destination_dir)
 
-    def _link(self, source, link_name, relative, canonical_path, ignore_missing):
+    def _link(self, source, link_name, relative, canonical_path, ignore_missing, dry_run):
         '''
         Links link_name to source.
 
@@ -149,13 +157,13 @@ class Link(dotbot.Plugin):
         # directory, and if source is relative, it will be relative to the
         # destination directory
         elif not self._exists(link_name) and (ignore_missing or self._exists(absolute_source)):
-            try:
-                os.symlink(source, destination)
-            except OSError:
-                self._log.warning('Linking failed %s -> %s' % (link_name, source))
-            else:
-                self._log.verbose('Creating link %s -> %s' % (link_name, source))
-                success = True
+            self._log.verbose('Creating link %s -> %s' % (link_name, source))
+            if not dry_run:
+                try:
+                    os.symlink(source, destination)
+                    success = True
+                except OSError:
+                    self._log.warning('Linking failed %s -> %s' % (link_name, source))
         elif self._exists(link_name) and not self._is_link(link_name):
             self._log.warning(
                 '%s already exists but is a regular file or directory' %
diff --git a/dotbot/plugins/shell.py b/dotbot/plugins/shell.py
index f0121e6..75d4dca 100644
--- a/dotbot/plugins/shell.py
+++ b/dotbot/plugins/shell.py
@@ -11,7 +11,7 @@ class Shell(dotbot.Plugin):
 
     _directive = 'shell'
 
-    def handle(self, directive, data):
+    def handle(self, directive, data, dry_run):
         success = True
         defaults = self._context.defaults().get('shell', {})
         for item in data:
@@ -38,6 +38,10 @@ class Shell(dotbot.Plugin):
                 self._log.info('%s' % msg)
             else:
                 self._log.info('%s [%s]' % (msg, cmd))
+
+            if dry_run:
+                continue
+
             ret = dotbot.util.shell_command(
                 cmd,
                 cwd=self._context.base_directory(),
@@ -48,8 +52,13 @@ class Shell(dotbot.Plugin):
             if ret != 0:
                 success = False
                 self._log.warning('Command [%s] failed' % cmd)
-        if success:
+
+        if dry_run:
+            self._log.verbose('shell/dry run: commands not executed')
+            success = False
+        elif success:
             self._log.verbose('All commands have been executed')
         else:
             self._log.error('Some commands were not successfully executed')
+
         return success