Implement conditional linking

README.md

@@ -192,6 +192,7 @@ Available extended configuration parameters:
 | `force` | Force removes the old target, file or folder, and forces a new link (default:false) |
 | `relative` | Use a relative path when creating the symlink (default:false, absolute links) |
 | `glob` | Treat a `*` character as a wildcard, and perform link operations on all of those matches (default:false) |
+| `if` | Execute this in your `$SHELL` and only link if it is successful. |
 
 #### Example
 

dotbot/plugins/link.py

@@ -2,6 +2,7 @@ import os
 import glob
 import shutil
 import dotbot
+import subprocess
 
 
 class Link(dotbot.Plugin):
@@ -31,6 +32,10 @@ class Link(dotbot.Plugin):
             use_glob = defaults.get('glob', False)
             if isinstance(source, dict):
                 # extended config
+                test = source.get('if')
+                if test is not None and not self._test_success(test):
+                    self._log.lowinfo('Skipping %s' % destination)
+                    continue
                 relative = source.get('relative', relative)
                 force = source.get('force', force)
                 relink = source.get('relink', relink)
@@ -90,6 +95,19 @@ class Link(dotbot.Plugin):
             self._log.error('Some links were not successfully set up')
         return success
 
+    def _test_success(self, command):
+        with open(os.devnull, 'w') as devnull:
+            ret = subprocess.call(
+                command,
+                shell=True,
+                stdout=devnull,
+                stderr=devnull,
+                executable=os.environ.get('SHELL'),
+            )
+        if ret != 0:
+            self._log.debug('Test \'%s\' returned false' % command)
+        return ret == 0
+
     def _default_source(self, destination, source):
         if source is None:
             basename = os.path.basename(destination)

test/tests/link-if.bash

@@ -0,0 +1,2 @@
+test_description='link if'
+. '../test-lib.bash'