Make plugins optional (#301)

Author: gatesn

README.rst

@@ -12,23 +12,41 @@ Python Language Server
 
 A Python 2.7 and 3.4+ implementation of the `Language Server Protocol`_.
 
-Feature Providers
------------------
-* Jedi_ for Completions, Definitions, Hover, References, Signature Help, and Symbols
+Installation
+------------
+
+The base language server requires Jedi_ to provide Completions, Definitions, Hover, References, Signature Help, and
+Symbols:
+
+``pip install python-language-server``
+
+If the respective dependencies are found, the following optional providers will be enabled:
+
 * Rope_ for Completions and renaming
 * Pyflakes_ linter to detect various errors
 * McCabe_ linter for complexity checking
 * pycodestyle_ linter for style checking
 * pydocstyle_ linter for docstring style checking
 * YAPF_ for code formatting
 
+Optional providers can be installed using the `extras` syntax. To install YAPF_ formatting for example:
+
+``pip install 'python-language-server[yapf]'``
+
+All optional providers can be installed using:
+
+``pip install 'python-language-server[all]'``
+
 3rd Party Plugins
 ~~~~~~~~~~~~~~~~~
 Installing these plugins will add extra functionality to the language server:
 
 * pyls-mypy_ Mypy type checking for Python 3
 * pyls-isort_ Isort import sort code formatting
 
+Please see the above repositories for examples on how to write plugins for the Python Language Server. Please file an
+issue if you require assistance writing a plugin.
+
 Configuration
 -------------
 
@@ -78,11 +96,6 @@ Document Formatting:
 
 .. image:: https://raw.githubusercontent.com/palantir/python-language-server/develop/resources/document-format.gif
 
-Installation
-------------
-
-``pip install python-language-server``
-
 Development
 -----------
 

pyls/config/config.py

@@ -1,5 +1,7 @@
 # Copyright 2017 Palantir Technologies, Inc.
 import logging
+import pkg_resources
+
 import pluggy
 
 from pyls import _utils, hookspecs, uris, PYLS
@@ -32,10 +34,23 @@ def __init__(self, root_uri, init_opts):
         self._pm.trace.root.setwriter(log.debug)
         self._pm.enable_tracing()
         self._pm.add_hookspecs(hookspecs)
+
+        # Pluggy will skip loading a plugin if it throws a DistributionNotFound exception.
+        # However I don't want all plugins to have to catch ImportError and re-throw. So here we'll filter
+        # out any entry points that throw ImportError assuming one or more of their dependencies isn't present.
+        for entry_point in pkg_resources.iter_entry_points(PYLS):
+            try:
+                entry_point.load()
+            except ImportError as e:
+                log.warn("Failed to load %s entry point '%s': %s", PYLS, entry_point.name, e)
+                self._pm.set_blocked(entry_point.name)
+
+        # Load the entry points into pluggy, having blocked any failing ones
         self._pm.load_setuptools_entrypoints(PYLS)
 
         for name, plugin in self._pm.list_name_plugin():
-            log.info("Loaded pyls plugin %s from %s", name, plugin)
+            if plugin is not None:
+                log.info("Loaded pyls plugin %s from %s", name, plugin)
 
         for plugin_conf in self._pm.hook.pyls_settings(config=self):
             self._plugin_settings = _utils.merge_dicts(self._plugin_settings, plugin_conf)

pyls/workspace.py

@@ -8,8 +8,6 @@
 import pkgutil
 
 import jedi
-from rope.base import libutils
-from rope.base.project import Project
 
 from . import lsp, uris, _utils
 
@@ -86,6 +84,8 @@ def __init__(self, root_uri, rpc_manager):
         self.__rope_config = None
 
     def _rope_project_builder(self, rope_config):
+        from rope.base.project import Project
+
         # TODO: we could keep track of dirty files and validate only those
         if self.__rope is None or self.__rope_config != rope_config:
             rope_folder = rope_config.get('ropeFolder')
@@ -169,6 +169,7 @@ def __str__(self):
         return str(self.uri)
 
     def _rope_resource(self, rope_config):
+        from rope.base import libutils
         return libutils.path_to_resource(self._rope_project_builder(rope_config), self.path)
 
     @property

setup.py

@@ -37,12 +37,6 @@
         'futures; python_version<"3.2"',
         'jedi>=0.10',
         'json-rpc==1.10.8',
-        'mccabe',
-        'pycodestyle',
-        'pydocstyle>=2.0.0',
-        'pyflakes>=1.6.0',
-        'rope>=0.10.5',
-        'yapf',
         'pluggy'
     ],
 
@@ -51,6 +45,20 @@
     # for example:
     # $ pip install -e .[test]
     extras_require={
+        'all': [
+            'mccabe',
+            'pycodestyle',
+            'pydocstyle>=2.0.0',
+            'pyflakes>=1.6.0',
+            'rope>-0.10.5',
+            'yapf',
+        ],
+        'mccabe': ['mccabe'],
+        'pycodestyle': ['pycodestyle'],
+        'pydocstyle': ['pydocstyle>=2.0.0'],
+        'pyflakes': ['pyflakes>=1.6.0'],
+        'rope': ['rope>0.10.5'],
+        'yapf': ['yapf'],
         'test': ['tox', 'versioneer', 'pytest', 'mock', 'pytest-cov', 'coverage'],
     },
 

tox.ini

@@ -26,6 +26,7 @@ deps =
     mock
     pytest-cov
     pylint
+extras = all
 
 [testenv:lint]
 commands =