Do not uninstall an already installed module when trying to install

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 - If module installation fails, the module directory is removed, so a subsequent installation doesn't instantly fail
 - Modules are now correctly unloaded when they raise a critical error
+- Installing a module that's already installed no longer uninstalls it (regression introduced in 0.5)
 
 ## [0.5] - 2017-03-22
 ### API changes

pext/__main__.py

@@ -692,6 +692,12 @@ def install_module(self, url: str, verbose=False, interactive=True) -> bool:
         dir_name = ModuleManager.add_prefix(module_name).replace('.', '_')
         module_name = ModuleManager.remove_prefix(module_name)
 
+        if os.path.exists(os.path.join(self.module_dir, dir_name)):
+            if verbose:
+                self._log_error('{} is already installed'.format(module_name))
+
+            return False
+
         if verbose:
             self._log('Installing {} from {}'.format(module_name, url))
 
@@ -723,6 +729,11 @@ def install_module(self, url: str, verbose=False, interactive=True) -> bool:
             except FileNotFoundError:
                 pass
 
+            try:
+                rmtree(os.path.join(self.module_dependencies_dir, dir_name))
+            except FileNotFoundError:
+                pass
+
             return False
 
         if verbose: