From 5b354164c5c4fbf6af1d58c185c7cd0510aedcbc Mon Sep 17 00:00:00 2001
From: Florian Bruhin <me@the-compiler.org>
Date: Mon, 10 Dec 2018 12:30:47 +0100
Subject: [PATCH] Make it possible for extensions to define init hooks

---
 qutebrowser/api/apitypes.py             |  1 +
 qutebrowser/api/hook.py                 | 35 +++++++++++++++++++++++++
 qutebrowser/components/__init__.py      |  2 +-
 qutebrowser/components/caretcommands.py |  2 +-
 qutebrowser/extensions/loader.py        | 35 ++++++++++++++++++++++++-
 5 files changed, 72 insertions(+), 3 deletions(-)
 create mode 100644 qutebrowser/api/hook.py

diff --git a/qutebrowser/api/apitypes.py b/qutebrowser/api/apitypes.py
index 9fec0a6cb..8fbc1a9a7 100644
--- a/qutebrowser/api/apitypes.py
+++ b/qutebrowser/api/apitypes.py
@@ -24,3 +24,4 @@ from qutebrowser.browser.browsertab import WebTabError, AbstractTab as Tab
 from qutebrowser.browser.webelem import (Error as WebElemError,
                                          AbstractWebElement as WebElement)
 from qutebrowser.utils.usertypes import ClickTarget, JsWorld
+from qutebrowser.extensions.loader import InitContext
diff --git a/qutebrowser/api/hook.py b/qutebrowser/api/hook.py
new file mode 100644
index 000000000..b468e91f5
--- /dev/null
+++ b/qutebrowser/api/hook.py
@@ -0,0 +1,35 @@
+# Copyright 2018 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Hooks for extensions."""
+
+import importlib
+import types
+import typing
+
+
+from qutebrowser.extensions import loader
+
+
+class init:  # noqa: N801,N806 pylint: disable=invalid-name
+
+    """Decorator to mark a function to run when initializing."""
+
+    def __call__(self, func: typing.Callable) -> typing.Callable:
+        module = importlib.import_module(func.__module__)
+        info = loader.add_module_info(module)
+        info.init_hook = func
diff --git a/qutebrowser/components/__init__.py b/qutebrowser/components/__init__.py
index b42c87fb6..1a13763bf 100644
--- a/qutebrowser/components/__init__.py
+++ b/qutebrowser/components/__init__.py
@@ -17,4 +17,4 @@
 # You should have received a copy of the GNU General Public License
 # along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
 
-"""qutebrowser "extensions" which only use the qutebrowser.API API."""
+"""qutebrowser "extensions" which only use the qutebrowser.api API."""
diff --git a/qutebrowser/components/caretcommands.py b/qutebrowser/components/caretcommands.py
index 4bab6b6c6..b9ecfab7c 100644
--- a/qutebrowser/components/caretcommands.py
+++ b/qutebrowser/components/caretcommands.py
@@ -20,7 +20,7 @@
 """Commands related to caret browsing."""
 
 
-from qutebrowser.api import cmdutils, apitypes
+from qutebrowser.api import cmdutils, apitypes, hook
 
 
 @cmdutils.register(modes=[cmdutils.KeyMode.caret])
diff --git a/qutebrowser/extensions/loader.py b/qutebrowser/extensions/loader.py
index b2481b969..f8cafa9e3 100644
--- a/qutebrowser/extensions/loader.py
+++ b/qutebrowser/extensions/loader.py
@@ -31,6 +31,23 @@ from qutebrowser import components
 from qutebrowser.utils import log
 
 
+@attr.s
+class InitContext:
+
+    """Context an extension gets in its init hook."""
+
+
+@attr.s
+class ModuleInfo:
+
+    """Information attached to an extension module.
+
+    This gets used by qutebrowser.api.hook.
+    """
+
+    init_hook = attr.ib(None)  # type: typing.Optional[typing.Callable]
+
+
 @attr.s
 class ExtensionInfo:
 
@@ -39,6 +56,13 @@ class ExtensionInfo:
     name = attr.ib()  # type: str
 
 
+def add_module_info(module: types.ModuleType) -> ModuleInfo:
+    """Add ModuleInfo to a module (if not added yet)."""
+    if not hasattr(module, '__qute_module_info'):
+        module.__qute_module_info = ModuleInfo()
+    return module.__qute_module_info
+
+
 def load_components() -> None:
     """Load everything from qutebrowser.components."""
     for info in walk_components():
@@ -88,5 +112,14 @@ def _walk_pyinstaller() -> typing.Iterator[ExtensionInfo]:
 
 
 def _load_component(info: ExtensionInfo) -> types.ModuleType:
+    """Load the given extension and run its init hook (if any)."""
     log.extensions.debug("Importing {}".format(info.name))
-    return importlib.import_module(info.name)
+    mod = importlib.import_module(info.name)
+
+    info = add_module_info(mod)
+    if info.init_hook is not None:
+        log.extensions.debug("Running init hook {!r}"
+                             .format(info.init_hook.__name__))
+        info.init_hook(InitContext())
+
+    return mod