Allow adding external directories to the plugin package

dosagelib/loader.py

@@ -5,11 +5,12 @@
 Functions to load plugin modules.
 
 Example usage:
-    modules = loader.get_plugin_modules()
-    plugins = loader.get_plugins(modules, PluginClass)
+    for module in loader.get_plugin_modules():
+        plugins.extend(loader.get_module_plugins(module, PluginClass))
 """
 import importlib
 import pkgutil
+import sys
 
 from .plugins import (__name__ as plugin_package, __path__ as plugin_path)
 from .output import out
@@ -44,16 +45,21 @@ def _get_all_modules_pyinstaller():
     return toc
 
 
-def get_plugins(modules, classobj):
-    """Find all class objects in all modules.
-    @param modules: the modules to search
-    @ptype modules: iterator of modules
-    @return: found classes
-    @rytpe: iterator of class objects
+def get_plugin_modules_from_dir(path, prefix='user_'):
+    """Load and import a directory of python files as if they were part of the
+    "plugins" package. (Mostly "stolen" from
+    https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly)
     """
-    for module in modules:
-        for plugin in get_module_plugins(module, classobj):
-            yield plugin
+    modules = []
+    for f in path.glob('*.py'):
+        name = plugin_package + "." + prefix + f.stem
+        # FIXME: Drop str() when this is Python 3.6+
+        spec = importlib.util.spec_from_file_location(name, str(f))
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[name] = module
+        spec.loader.exec_module(module)
+        modules.append(module)
+    return modules
 
 
 def get_module_plugins(module, classobj):

dosagelib/scraper.py

@@ -542,7 +542,7 @@ class Cache:
     slow.
     """
     def __init__(self):
-        self.data = None
+        self.data = []
 
     def find(self, comic, multiple_allowed=False):
         """Get a list comic scraper objects.
@@ -574,12 +574,41 @@ class Cache:
 
     def load(self):
         out.debug("Loading comic modules...")
-        modules = loader.get_plugin_modules()
-        plugins = list(loader.get_plugins(modules, Scraper))
-        self.data = list([m for x in plugins for m in x.getmodules()])
+        modules = 0
+        classes = 0
+        for module in loader.get_plugin_modules():
+            modules += 1
+            classes += self.addmodule(module)
         self.validate()
-        out.debug("... %d modules loaded from %d classes." % (
-            len(self.data), len(plugins)))
+        out.debug("... %d scrapers loaded from %d classes in %d modules." % (
+            len(self.data), classes, modules))
+
+    def adddir(self, path):
+        """Add an additional directory with python modules to the scraper list.
+        These are handled as if the were part of the plugins package.
+        """
+        if not self.data:
+            self.load()
+        modules = 0
+        classes = 0
+        out.debug("Loading user scrapers from '{}'...".format(path))
+        for module in loader.get_plugin_modules_from_dir(path):
+            modules += 1
+            classes += self.addmodule(module)
+        self.validate()
+        if classes > 0:
+            out.debug("Added %d user classes from %d modules." % (
+                classes, modules))
+
+    def addmodule(self, module):
+        """Adds all valid plugin classes from the specified module to the cache.
+        @return: number of classes added
+        """
+        classes = 0
+        for plugin in loader.get_module_plugins(module, Scraper):
+            classes += 1
+            self.data.extend(plugin.getmodules())
+        return classes
 
     def get(self, include_removed=False):
         """Find all comic scraper classes in the plugins directory.

tests/mocks/plugins/dummy.py

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: MIT
+# Copyright (C) 2020 Tobias Gruetzmacher
+from ..scraper import _ParserScraper
+
+
+class ADummyTestScraper(_ParserScraper):
+    url = 'https://dummy.example/'

tests/test_scraper.py

@@ -1,7 +1,10 @@
 # SPDX-License-Identifier: MIT
 # Copyright (C) 2013-2014 Bastian Kleineidam
 # Copyright (C) 2015-2020 Tobias Gruetzmacher
+from pathlib import Path
+
 import pytest
+
 from dosagelib.scraper import scrapers
 
 
@@ -24,3 +27,9 @@ class TestScraper(object):
     def test_find_scrapers_error(self):
         with pytest.raises(ValueError, match='empty comic name'):
             scrapers.find('')
+
+    def test_user_dir(self):
+        oldlen = len(scrapers.get())
+        scrapers.adddir(Path(__file__).parent / 'mocks' / 'plugins')
+        assert len(scrapers.get()) == oldlen + 1
+        assert len(scrapers.find('ADummyTestScraper')) == 1