Add a :config-source command

See #2794

doc/help/commands.asciidoc

@@ -33,6 +33,7 @@ It is possible to run or bind multiple commands by separating them with `;;`.
 |<<close,close>>|Close the current window.
 |<<config-clear,config-clear>>|Set all settings back to their default.
 |<<config-cycle,config-cycle>>|Cycle an option between multiple values.
+|<<config-source,config-source>>|Read a config.py file.
 |<<config-unset,config-unset>>|Unset an option.
 |<<download,download>>|Download a given URL, or current page if no URL given.
 |<<download-cancel,download-cancel>>|Cancel the last/[count]th download.
@@ -228,6 +229,19 @@ Cycle an option between multiple values.
 * +*-t*+, +*--temp*+: Set value temporarily until qutebrowser is closed.
 * +*-p*+, +*--print*+: Print the value after setting.
 
+[[config-source]]
+=== config-source
+Syntax: +:config-source [*--clear*] ['filename']+
+
+Read a config.py file.
+
+==== positional arguments
+* +'filename'+: The file to load. If not given, loads the default config.py.
+
+
+==== optional arguments
+* +*-c*+, +*--clear*+: Clear current settings first.
+
 [[config-unset]]
 === config-unset
 Syntax: +:config-unset [*--temp*] 'option'+

qutebrowser/config/configcommands.py

@@ -19,14 +19,15 @@
 
 """Commands related to the configuration."""
 
+import os.path
 import contextlib
 
 from PyQt5.QtCore import QUrl
 
 from qutebrowser.commands import cmdexc, cmdutils
 from qutebrowser.completion.models import configmodel
-from qutebrowser.utils import objreg, utils, message
+from qutebrowser.utils import objreg, utils, message, standarddir
-from qutebrowser.config import configtypes, configexc
+from qutebrowser.config import configtypes, configexc, configfiles
 
 
 class ConfigCommands:
@@ -203,3 +204,25 @@ class ConfigCommands:
                   removed.
         """
         self._config.clear(save_yaml=save)
+
+    @cmdutils.register(instance='config-commands')
+    def config_source(self, filename=None, clear=False):
+        """Read a config.py file.
+
+        Args:
+            filename: The file to load. If not given, loads the default
+                      config.py.
+            clear: Clear current settings first.
+        """
+        if filename is None:
+            filename = os.path.join(standarddir.config(), 'config.py')
+        else:
+            filename = os.path.expanduser(filename)
+
+        if clear:
+            self.config_clear()
+
+        try:
+            configfiles.read_config_py(filename)
+        except configexc.ConfigFileErrors as e:
+            raise cmdexc.CommandError(e)

tests/unit/config/test_configcommands.py

@@ -263,6 +263,45 @@ class TestUnsetAndClear:
             assert config_stub._yaml[name] == 'never'
 
 
+class TestSource:
+
+    """Test :config-source."""
+
+    pytestmark = pytest.mark.usefixtures('config_tmpdir', 'data_tmpdir')
+
+    @pytest.mark.parametrize('use_default_dir', [True, False])
+    @pytest.mark.parametrize('clear', [True, False])
+    def test_config_source(self, tmpdir, commands, config_stub, config_tmpdir,
+                           use_default_dir, clear):
+        assert config_stub.val.content.javascript.enabled
+        config_stub.val.ignore_case = 'always'
+
+        if use_default_dir:
+            pyfile = config_tmpdir / 'config.py'
+            arg = None
+        else:
+            pyfile = tmpdir / 'sourced.py'
+            arg = str(pyfile)
+        pyfile.write_text('c.content.javascript.enabled = False\n',
+                          encoding='utf-8')
+
+        commands.config_source(arg, clear=clear)
+
+        assert not config_stub.val.content.javascript.enabled
+        assert config_stub.val.ignore_case == ('smart' if clear else 'always')
+
+    def test_errors(self, commands, config_tmpdir):
+        pyfile = config_tmpdir / 'config.py'
+        pyfile.write_text('c.foo = 42', encoding='utf-8')
+
+        with pytest.raises(cmdexc.CommandError) as excinfo:
+            commands.config_source()
+
+        expected = ("Errors occurred while reading config.py:\n"
+                    "  While setting 'foo': No option 'foo'")
+        assert str(excinfo.value) == expected
+
+
 class TestBind:
 
     """Tests for :bind and :unbind."""