feat(app.ipython#99): respect CFG < ENV < CLI order

traitlets/config/application.py

@@ -65,7 +65,7 @@
 #-----------------------------------------------------------------------------
 
 CFG_RANK = 0
-ENV_RANK = 10
+ENV_RANK = 10  # Informative; used literal in :meth:`Configurable.update_config()`.
 CLI_RANK = 20
 
 

traitlets/config/configurable.py

@@ -159,7 +159,15 @@ def _load_config(self, cfg, section_names=None, traits=None):
         # hold trait notifications until after all config has been loaded
         with self.hold_trait_notifications():
             for name, config_value in my_config.items():
-                if name in traits:
+                trait = traits.get(name)
+                if trait:
+                    env_value = trait.get_env_value()
+                    ## priority: file-conf < env-vars < cli-options
+                    #  See :data:`application.ENV_RANK`
+                    if env_value is not None and my_config.rank_of(name) < 10:
+                        setattr(self, name, env_value)
+                        continue
+
                     if isinstance(config_value, LazyConfigValue):
                         # ConfigValue is a wrapper for using append / update on containers
                         # without having to copy the initial value

traitlets/config/tests/test_application.py

@@ -26,14 +26,17 @@
 
 from traitlets.config.configurable import Configurable
 from traitlets.config.loader import Config
-from traitlets.tests.utils import get_output_error_code, check_help_output, check_help_all_output
+from traitlets.tests.utils import (
+    get_output_error_code, check_help_output, check_help_all_output
+)
 
 from traitlets.config.application import (
-    Application
+    Application, CLI_RANK
 )
 
 from ipython_genutils.tempdir import TemporaryDirectory
 from traitlets import (
+    default,
     HasTraits,
     Bool, Bytes, Unicode, Integer, List, Tuple, Set, Dict
 )
@@ -430,7 +433,7 @@ def test_generate_config_file(self):
     def test_generate_config_file_classes_to_include(self):
         class NotInConfig(HasTraits):
             from_hidden = Unicode('x', help="""From hidden class
-            
+
             Details about from_hidden.
             """).tag(config=True)
 
@@ -623,7 +626,7 @@ def test_show_config(capsys):
     cfg.MyApp.i = 5
     # don't show empty
     cfg.OtherApp
-    
+
     app = MyApp(config=cfg, show_config=True)
     app.start()
     out, err = capsys.readouterr()
@@ -636,14 +639,93 @@ def test_show_config_json(capsys):
     cfg = Config()
     cfg.MyApp.i = 5
     cfg.OtherApp
-    
+
     app = MyApp(config=cfg, show_config_json=True)
     app.start()
     out, err = capsys.readouterr()
     displayed = json.loads(out)
     assert Config(displayed) == cfg
 
 
+def test_env_vars_priority(monkeypatch):
+    class Conf(Configurable):
+        b = Unicode().tag(config=True, envvar='MY_ENVVAR')
+
+        @default('b')
+        def set_a_dyn(self):
+            return 'dyn'
+
+    class App(Application):
+        a = Unicode('def').tag(config=True, envvar='MY_ENVVAR')
+        aliases = {'a': 'App.a', 'b': 'Conf.b'}
+
+        def reconf(self):
+            self.conf = Conf(parent=self)
+
+    exp_no_envvar = {
+        'init': ('def', 'dyn'),  # values after construction
+        'set': ('set', 'set'),  # values after direct assignment
+        'cfg': ('cfg', 'cfg'),  # values after `update_config()
+        'cli': ('cli', 'cli'),  # values after prsing cmd-line args
+    }
+    exp_with_envvar = {
+        'init': ('env', 'env'),
+        'set': ('set', 'set'),
+        'cfg': ('env', 'env'),
+        'cli': ('cli', 'cli'),
+    }
+
+    def check_priority(exp):
+        import copy
+
+        cfg = Config()
+        cfg.App.a = cfg.Conf.b = 'cfg'
+
+        cfg_set = Config()
+        cfg_set.App.a = cfg_set.Conf.b = 'set'
+        cfg_set.set_default_rank(CLI_RANK + 10)
+
+        app = App(); app.reconf()
+        assert (app.a, app.conf.b) == exp['init']
+
+        app.update_config(cfg); app.reconf()
+        assert (app.a, app.conf.b) == exp['cfg']
+
+        app.update_config(cfg_set); app.reconf()
+        assert (app.a, app.conf.b) == exp['set']
+
+        ## Above had been check by test_config.
+        ## Now add cmd-line into the mix.
+
+        app.parse_command_line([]); app.reconf()
+        assert (app.a, app.conf.b) == exp['set']  # empty-cli do nothing.
+
+        app.parse_command_line('-a=cli -b=cli'.split()); app.reconf()
+        assert (app.a, app.conf.b) == exp['set']  # CLI lower than explict-set.
+
+        app = App(config=cfg); app.reconf()
+        assert (app.a, app.conf.b) == exp['cfg']
+
+        app.parse_command_line('-a=cli -b=cli'.split()); app.reconf()
+        assert (app.a, app.conf.b) == exp['cli']
+
+        app.update_config(cfg_set); app.reconf()
+        assert (app.a, app.conf.b) == exp['set']
+
+        app = App(); app.reconf()
+        assert (app.a, app.conf.b) == exp['init']
+
+        app.parse_command_line('-a=cli -b=cli'.split()); app.reconf()
+        assert (app.a, app.conf.b) == exp['cli']
+
+        app.update_config(cfg_set); app.reconf()
+        assert (app.a, app.conf.b) == exp['set']
+
+    check_priority(exp_no_envvar)
+    monkeypatch.setenv('MY_ENVVAR', 'env')
+    check_priority(exp_with_envvar)
+
+
 if __name__ == '__main__':
     # for test_help_output:
     MyApp.launch_instance()

traitlets/config/tests/test_configurable.py

@@ -18,8 +18,8 @@
 )
 
 from traitlets.traitlets import (
-    Integer, Float, Unicode, List, Dict, Set, Enum, FuzzyEnum,
-    CaselessStrEnum, _deprecations_shown, validate,
+    Integer, CInt, Float, Unicode, List, Dict, Set, Enum, FuzzyEnum,
+    CaselessStrEnum, _deprecations_shown, validate, default
 )
 
 from traitlets.config.loader import Config
@@ -311,7 +311,6 @@ class MyConf4(Configurable):
                            cls4_cfg.index(enum_choices_str))
 
 
-
 class TestSingletonConfigurable(TestCase):
 
     def test_instance(self):
@@ -670,3 +669,79 @@ class A(Configurable):
     assert len(matches) == expected_nmatches
     if expected_nmatches > 1:
         assert matches[1].group(1) == '(only)'
+
+
+def test_environment_variable_default(monkeypatch):
+    class A(Configurable):
+        b = CInt(allow_none=True).tag(config=True, envvar='MY_ENVVAR')
+
+    cfg = Config()
+    cfg.A.b = 2
+
+    a = A()
+    assert a.b == 0
+    a = A(config=cfg)
+    assert a.b == 2
+
+    monkeypatch.setenv('MY_ENVVAR', '1')
+
+    a = A()
+    assert a.b == 1  # env-var has precendance.
+
+    a = A(config=cfg)
+    assert a.b == 1  # env-var has precendance.
+
+    a.b = 3
+    assert a.b == 3  # Direct assignments override env-var.
+    a.b = None
+    assert a.b is None
+
+
+def test_env_vars_priority(monkeypatch):
+    class Conf(Configurable):
+        a = Unicode('def').tag(config=True, envvar='MY_ENVVAR')
+        b = Unicode().tag(config=True, envvar='MY_ENVVAR')
+        aliases = {'def': 'App.a', 'dyn': 'App.b'}
+
+        @default('b')
+        def set_a_dyn(self):
+            return 'dyn'
+
+    exp_no_envvar = {
+        'init': ('def', 'dyn'),  # values after "empty" construction
+        'set': ('set', 'set'),  # values after direct assignment
+        'cfg': ('cfg', 'cfg'),  # values after `update_config()
+    }
+    exp_with_envvar = {
+        'init': ('env', 'env'),
+        'set': ('set', 'set'),
+        'cfg': ('env', 'env'),
+    }
+
+    def check_priority(exp):
+        cfg = Config()
+        cfg.Conf.a = cfg.Conf.b = 'cfg'
+
+        conf = Conf()
+        assert (conf.a, conf.b) == exp['init']
+        conf.update_config(cfg)
+        assert (conf.a, conf.b) == exp['cfg']
+
+        conf.a = conf.b = 'set'
+        assert (conf.a, conf.b) == exp['set']
+
+        conf.update_config(cfg)
+        assert (conf.a, conf.b) == exp['cfg']
+
+        conf = Conf(a='set', b='set')
+        assert (conf.a, conf.b) == exp['set']
+
+        conf = Conf(config=cfg, a='set', b='set')
+        assert (conf.a, conf.b) == exp['set']
+
+        conf = Conf(config=cfg)
+        assert (conf.a, conf.b) == exp['cfg']
+
+    check_priority(exp_no_envvar)
+    monkeypatch.setenv('MY_ENVVAR', 'env')
+    check_priority(exp_with_envvar)