configuration: add delete_config()

We currently have no way to delete options once set. This is not good
for users that want to delete things so they go back to their default
values. Add a library API and tests for this; we'll extend the config
command with options that use them next.

Signed-off-by: Marti Bolivar <marti.bolivar@nordicsemi.no>

src/west/configuration.py

@@ -118,6 +118,53 @@ def update_config(section, key, value, configfile=ConfigFile.LOCAL):
     updater[section][key] = value
     updater.write()
 
+def delete_config(section, key, configfile=None):
+    '''Delete the option section.key from the given file or files.
+
+    :param section: section whose key to delete
+    :param key: key to delete
+    :param configfile: If ConfigFile.ALL, delete section.key in all files
+                       where it is set.
+                       If None, delete only from the highest-precedence
+                       global or local file where it is set, allowing
+                       lower-precedence values to take effect again.
+                       If a list of ConfigFile enumerators, delete
+                       from those files.
+                       Otherwise, delete from the given ConfigFile.
+
+    Deleting the only key in a section deletes the entire section.
+
+    If the option is not set, KeyError is raised.'''
+    stop = False
+    if configfile is None:
+        to_check = [_location(x) for x in
+                    [ConfigFile.LOCAL, ConfigFile.GLOBAL]]
+        stop = True
+    elif configfile == ConfigFile.ALL:
+        to_check = [_location(x) for x in
+                    [ConfigFile.SYSTEM, ConfigFile.GLOBAL, ConfigFile.LOCAL]]
+    elif isinstance(configfile, ConfigFile):
+        to_check = [_location(configfile)]
+    else:
+        to_check = [_location(x) for x in configfile]
+
+    found = False
+    for path in to_check:
+        cobj = configobj.ConfigObj(path)
+        if section not in cobj or key not in cobj[section]:
+            continue
+
+        del cobj[section][key]
+        if not cobj[section].items():
+            del cobj[section]
+        cobj.write()
+        found = True
+        if stop:
+            break
+
+    if not found:
+        raise KeyError('{}.{}'.format(section, key))
+
 def _location(cfg):
     # Making this a function that gets called each time you ask for a
     # configuration file makes it respect updated environment

tests/test_config.py

@@ -235,6 +235,113 @@ def test_local_creation():
     assert 'pytest' not in cfg(f=GLOBAL)
     assert cfg(f=LOCAL)['pytest']['key'] == 'val'
 
+@patch('west.configuration._location', new=tstloc)
+def test_delete_basic():
+    # Basic deletion test: write local, verify global and system deletions
+    # don't work, then delete local does work.
+    config.update_config('pytest', 'key', 'val', configfile=LOCAL)
+    assert cfg(f=ALL)['pytest']['key'] == 'val'
+    with pytest.raises(KeyError):
+        config.delete_config('pytest', 'key', configfile=SYSTEM)
+    with pytest.raises(KeyError):
+        config.delete_config('pytest', 'key', configfile=GLOBAL)
+    config.delete_config('pytest', 'key', configfile=LOCAL)
+    assert 'pytest' not in cfg(f=ALL)
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_all():
+    # Deleting ConfigFile.ALL should delete from everywhere.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=ALL)
+    assert 'pytest' not in cfg(f=ALL)
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_none():
+    # Deleting None should delete from lowest-precedence global or
+    # local file only.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=None)
+    assert cfg(f=ALL)['pytest']['key'] == 'global'
+    config.delete_config('pytest', 'key', configfile=None)
+    assert cfg(f=ALL)['pytest']['key'] == 'system'
+    with pytest.raises(KeyError):
+        config.delete_config('pytest', 'key', configfile=None)
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_list():
+    # Test delete of a list of places.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=[GLOBAL, LOCAL])
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert 'pytest' not in cfg(f=GLOBAL)
+    assert 'pytest' not in cfg(f=LOCAL)
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_system():
+    # Test SYSTEM-only delete.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=SYSTEM)
+    assert 'pytest' not in cfg(f=SYSTEM)
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_global():
+    # Test GLOBAL-only delete.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=GLOBAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert 'pytest' not in cfg(f=GLOBAL)
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_local():
+    # Test LOCAL-only delete.
+    config.update_config('pytest', 'key', 'system', configfile=SYSTEM)
+    config.update_config('pytest', 'key', 'global', configfile=GLOBAL)
+    config.update_config('pytest', 'key', 'local', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert cfg(f=LOCAL)['pytest']['key'] == 'local'
+    config.delete_config('pytest', 'key', configfile=LOCAL)
+    assert cfg(f=SYSTEM)['pytest']['key'] == 'system'
+    assert cfg(f=GLOBAL)['pytest']['key'] == 'global'
+    assert 'pytest' not in cfg(f=LOCAL)
+
+@patch('west.configuration._location', new=tstloc)
+def test_delete_local_one():
+    # Test LOCAL-only delete of one option doesn't affect the other.
+    config.update_config('pytest', 'key1', 'foo', configfile=LOCAL)
+    config.update_config('pytest', 'key2', 'bar', configfile=LOCAL)
+    config.delete_config('pytest', 'key1', configfile=LOCAL)
+    assert 'pytest' in cfg(f=LOCAL)
+    assert cfg(f=LOCAL)['pytest']['key2'] == 'bar'
+
 def test_default_config():
     # Writing to a value without a config destination should default
     # to --local.