Add server plugin system (#1447)

* Add server plugin system

Plugins are optional modules loaded at runtime. Specification:
* Plugins are loaded from the server.plugins module (directory
  server/plugins)
* The import_plugins method is run as part of the initialization of the
  server module in __init__.py

* Add plugins to the EB build process

* Remove bit of dead code

* Respond to feedback from @bmccandless

server/test/__init__.py

@@ -1,4 +1,6 @@
+import random
 import shutil
+import string
 import tempfile
 from os import path, popen
 
@@ -74,3 +76,7 @@ def app_config(data_locator, backed=False):
     config.update(**args)
     config.complete_config()
     return config
+
+
+def random_string(n):
+    return "".join(random.choice(string.ascii_letters) for _ in range(n))

server/test/test_cxg_adaptor.py

@@ -7,7 +7,6 @@ from server.test.test_datasets.fixtures import pbmc3k_colors
 
 
 class TestCxgAdaptor(unittest.TestCase):
-
     def test_get_colors(self):
         data = self.get_data("pbmc3k.cxg")
         self.assertDictEqual(data.get_colors(), pbmc3k_colors)

server/test/test_cxgtool.py

@@ -1,6 +1,4 @@
-import random
 import shutil
-import string
 import unittest
 
 import anndata
@@ -8,7 +6,7 @@ import anndata
 from server.common.data_locator import DataLocator
 from server.converters.cxgtool import write_cxg
 from server.data_cxg.cxg_adaptor import CxgAdaptor
-from server.test import PROJECT_ROOT, app_config
+from server.test import PROJECT_ROOT, app_config, random_string
 from server.test.test_datasets.fixtures import pbmc3k_colors
 
 
@@ -31,8 +29,8 @@ class TestCxgAdaptor(unittest.TestCase):
         self.assertEqual(data.get_colors(), {})
 
     def convert_pbmc3k(self, **kwargs):
-        random_string = "".join(random.choice(string.ascii_letters) for _ in range(8))
-        data_locator = f"/tmp/test_{random_string}.cxg"
+        rand_str = random_string(8)
+        data_locator = f"/tmp/test_{rand_str}.cxg"
         self.fixtures.append(data_locator)
         source_h5ad = anndata.read_h5ad(f"{PROJECT_ROOT}/example-dataset/pbmc3k.h5ad")
         write_cxg(adata=source_h5ad, container=data_locator, title="pbmc3k", **kwargs)

server/test/test_plugins.py

@@ -0,0 +1,34 @@
+import os
+import shutil
+import unittest
+
+from server.common.utils import import_plugins
+from server.test import PROJECT_ROOT, random_string
+
+
+class TestPlugins(unittest.TestCase):
+    """ Test plugin import functionality """
+
+    plugins_dir = f"{PROJECT_ROOT}/server/test/plugins"
+    test_plugin_path = f"{plugins_dir}/foo.py"
+    secret = random_string(8)
+
+    @classmethod
+    def setUpClass(cls) -> None:
+        if not os.path.isdir(cls.plugins_dir):
+            os.mkdir(cls.plugins_dir)
+        with open(cls.test_plugin_path, "w") as fh:
+            fh.write(f'SECRET = "{cls.secret}"\n')
+
+    @classmethod
+    def tearDownClass(cls) -> None:
+        if os.path.isdir(cls.plugins_dir):
+            shutil.rmtree(cls.plugins_dir)
+
+    def test_import_plugins(self):
+        self.assertTrue(os.path.isfile(self.test_plugin_path))
+        loaded_modules = import_plugins("server.test.plugins")
+        # test that import plugins found the file
+        self.assertEqual(["server.test.plugins.foo"], [ele.__name__ for ele in loaded_modules])
+        # test that the module was properly executed
+        self.assertEqual(self.secret, loaded_modules[0].SECRET)