Add a config.source() method

doc/changelog.asciidoc

@@ -29,6 +29,7 @@ Added
   command in the completion.
 - New `:tab-give` and `:tab-take` commands, to give tabs to another window, or
   take them from another window.
+- New `config.source(...)` method for `config.py` to source another file.
 
 Fixed
 ~~~~~

doc/help/configuring.asciidoc

@@ -238,6 +238,9 @@ that via `import utils` as well.
 While it's in some cases possible to import code from the qutebrowser
 installation, doing so is unsupported and discouraged.
 
+To read config data from a different file with `c` and `config` available, you
+can use `config.source('otherfile.py')` in your `config.py`.
+
 Getting the config directory
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

qutebrowser/config/configfiles.py

@@ -259,6 +259,15 @@ class ConfigAPI:
         with self._handle_error('unbinding', key):
             self._keyconfig.unbind(key, mode=mode)
 
+    def source(self, filename):
+        if not os.path.isabs(filename):
+            filename = str(self.configdir / filename)
+
+        try:
+            read_config_py(filename)
+        except configexc.ConfigFileErrors as e:
+            self.errors += e.errors
+
 
 class ConfigPyWriter:
 

tests/unit/config/test_configfiles.py

@@ -580,6 +580,38 @@ class TestConfigPy:
         assert isinstance(error.exception, ZeroDivisionError)
         assert error.traceback is not None
 
+    @pytest.mark.parametrize('location', ['abs', 'rel'])
+    def test_source(self, tmpdir, confpy, location):
+        if location == 'abs':
+            subfile = tmpdir / 'subfile.py'
+            arg = str(subfile)
+        else:
+            subfile = tmpdir / 'config' / 'subfile.py'
+            arg = 'subfile.py'
+
+        subfile.write_text("c.content.javascript.enabled = False",
+                           encoding='utf-8')
+        confpy.write("config.source('{}')".format(arg))
+        confpy.read()
+
+        assert not config.instance._values['content.javascript.enabled']
+
+    def test_source_errors(self, tmpdir, confpy):
+        subfile = tmpdir / 'config' / 'subfile.py'
+        subfile.write_text("c.foo = 42", encoding='utf-8')
+        confpy.write("config.source('subfile.py')")
+        error = confpy.read(error=True)
+
+        assert error.text == "While setting 'foo'"
+        assert isinstance(error.exception, configexc.NoOptionError)
+
+    def test_source_not_found(self, confpy):
+        confpy.write("config.source('doesnotexist.py')")
+        error = confpy.read(error=True)
+
+        assert error.text == "Error while reading doesnotexist.py"
+        assert isinstance(error.exception, FileNotFoundError)
+
 
 class TestConfigPyWriter: