Add deprecated Field parameter

The deprecation message gets appended to the docstring, so if the Config
is saved it rides along "for free". It also emits a warning if that field is
set later.

python/lsst/pex/config/config.py

@@ -29,6 +29,7 @@
 import copy
 import tempfile
 import shutil
+import warnings
 
 from .comparison import getComparisonName, compareScalars, compareConfigs
 from .callStack import getStackFrame, getCallStack
@@ -208,6 +209,9 @@ class Field:
         This sets whether the field is considered optional, and therefore
         doesn't need to be set by the user. When `False`,
         `lsst.pex.config.Config.validate` fails if the field's value is `None`.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     Raises
     ------
@@ -263,24 +267,32 @@ class Field:
     """Supported data types for field values (`set` of types).
     """
 
-    def __init__(self, doc, dtype, default=None, check=None, optional=False):
+    def __init__(self, doc, dtype, default=None, check=None, optional=False, deprecated=None):
         if dtype not in self.supportedTypes:
             raise ValueError("Unsupported Field dtype %s" % _typeStr(dtype))
 
         source = getStackFrame()
-        self._setup(doc=doc, dtype=dtype, default=default, check=check, optional=optional, source=source)
+        self._setup(doc=doc, dtype=dtype, default=default, check=check, optional=optional, source=source,
+                    deprecated=deprecated)
 
-    def _setup(self, doc, dtype, default, check, optional, source):
+    def _setup(self, doc, dtype, default, check, optional, source, deprecated):
         """Set attributes, usually during initialization.
         """
         self.dtype = dtype
         """Data type for the field.
         """
 
+        # append the deprecation message to the docstring.
+        if deprecated is not None:
+            doc = f"{doc} Deprecated: {deprecated}"
         self.doc = doc
         """A description of the field (`str`).
         """
 
+        self.deprecated = deprecated
+        """If not None, a description of why this field is deprecated (`str`).
+        """
+
         self.__doc__ = f"{doc} (`{dtype.__name__}`"
         if optional or default is not None:
             self.__doc__ += f", default ``{default!r}``"
@@ -1258,6 +1270,10 @@ def __setattr__(self, attr, value, at=None, label="assignment"):
         non-existent field.
         """
         if attr in self._fields:
+            if self._fields[attr].deprecated is not None:
+                fullname = _joinNamePath(self._name, self._fields[attr].name)
+                warnings.warn(f"Config field {fullname} is deprecated: {self._fields[attr].deprecated}",
+                              FutureWarning)
             if at is None:
                 at = getCallStack()
             # This allows Field descriptors to work.

python/lsst/pex/config/configChoiceField.py

@@ -327,6 +327,9 @@ class ConfigChoiceField(Field):
         If `False`, the field allows only a single selection. In this case,
         set the active config by assigning the config's key from the
         ``typemap`` to the field's ``name`` attribute (see *Examples*).
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -406,10 +409,10 @@ class ConfigChoiceField(Field):
 
     instanceDictClass = ConfigInstanceDict
 
-    def __init__(self, doc, typemap, default=None, optional=False, multi=False):
+    def __init__(self, doc, typemap, default=None, optional=False, multi=False, deprecated=None):
         source = getStackFrame()
         self._setup(doc=doc, dtype=self.instanceDictClass, default=default, check=None, optional=optional,
-                    source=source)
+                    source=source, deprecated=deprecated)
         self.typemap = typemap
         self.multi = multi
 

python/lsst/pex/config/configDictField.py

@@ -107,6 +107,9 @@ class ConfigDictField(DictField):
     optional : `bool`, optional
         If `True`, this configuration `~lsst.pex.config.Field` is *optional*.
         Default is `True`.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     Raises
     ------
@@ -139,10 +142,11 @@ class ConfigDictField(DictField):
 
     DictClass = ConfigDict
 
-    def __init__(self, doc, keytype, itemtype, default=None, optional=False, dictCheck=None, itemCheck=None):
+    def __init__(self, doc, keytype, itemtype, default=None, optional=False, dictCheck=None, itemCheck=None,
+                 deprecated=None):
         source = getStackFrame()
         self._setup(doc=doc, dtype=ConfigDict, default=default, check=None,
-                    optional=optional, source=source)
+                    optional=optional, source=source, deprecated=deprecated)
         if keytype not in self.supportedTypes:
             raise ValueError("'keytype' %s is not a supported type" %
                              _typeStr(keytype))

python/lsst/pex/config/configField.py

@@ -48,6 +48,9 @@ class ConfigField(Field):
     check : callable, optional
         A callback function that validates the field's value, returning `True`
         if the value is valid, and `False` otherwise.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -70,15 +73,15 @@ class ConfigField(Field):
     configuration.
     """
 
-    def __init__(self, doc, dtype, default=None, check=None):
+    def __init__(self, doc, dtype, default=None, check=None, deprecated=None):
         if not issubclass(dtype, Config):
             raise ValueError("dtype=%s is not a subclass of Config" %
                              _typeStr(dtype))
         if default is None:
             default = dtype
         source = getStackFrame()
         self._setup(doc=doc, dtype=dtype, default=default, check=check,
-                    optional=False, source=source)
+                    optional=False, source=source, deprecated=deprecated)
 
     def __get__(self, instance, owner=None):
         if instance is None or not isinstance(instance, Config):

python/lsst/pex/config/configurableField.py

@@ -186,6 +186,9 @@ class of the ``target``. If ``ConfigClass`` is unset then
         Callable that takes the field's value (the ``target``) as its only
         positional argument, and returns `True` if the ``target`` is valid (and
         `False` otherwise).
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -247,7 +250,7 @@ def validateTarget(self, target, ConfigClass):
                              "(must have '__module__' and '__name__' attributes)")
         return ConfigClass
 
-    def __init__(self, doc, target, ConfigClass=None, default=None, check=None):
+    def __init__(self, doc, target, ConfigClass=None, default=None, check=None, deprecated=None):
         ConfigClass = self.validateTarget(target, ConfigClass)
 
         if default is None:
@@ -258,7 +261,7 @@ def __init__(self, doc, target, ConfigClass=None, default=None, check=None):
 
         source = getStackFrame()
         self._setup(doc=doc, dtype=ConfigurableInstance, default=default,
-                    check=check, optional=False, source=source)
+                    check=check, optional=False, source=source, deprecated=deprecated)
         self.target = target
         self.ConfigClass = ConfigClass
 

python/lsst/pex/config/dictField.py

@@ -161,6 +161,9 @@ class DictField(Field):
         A function that validates the dictionary as a whole.
     itemCheck : callable
         A function that validates individual mapping values.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -193,10 +196,11 @@ class DictField(Field):
 
     DictClass = Dict
 
-    def __init__(self, doc, keytype, itemtype, default=None, optional=False, dictCheck=None, itemCheck=None):
+    def __init__(self, doc, keytype, itemtype, default=None, optional=False, dictCheck=None, itemCheck=None,
+                 deprecated=None):
         source = getStackFrame()
         self._setup(doc=doc, dtype=Dict, default=default, check=None,
-                    optional=optional, source=source)
+                    optional=optional, source=source, deprecated=deprecated)
         if keytype not in self.supportedTypes:
             raise ValueError("'keytype' %s is not a supported type" %
                              _typeStr(keytype))

python/lsst/pex/config/listField.py

@@ -236,6 +236,9 @@ class ListField(Field):
     maxLength : `int`, optional
         If set, this field must contain *no more than* ``maxLength`` number of
         items.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -251,7 +254,8 @@ class ListField(Field):
     """
     def __init__(self, doc, dtype, default=None, optional=False,
                  listCheck=None, itemCheck=None,
-                 length=None, minLength=None, maxLength=None):
+                 length=None, minLength=None, maxLength=None,
+                 deprecated=None):
         if dtype not in Field.supportedTypes:
             raise ValueError("Unsupported dtype %s" % _typeStr(dtype))
         if length is not None:
@@ -273,7 +277,8 @@ def __init__(self, doc, dtype, default=None, optional=False,
             raise ValueError("'itemCheck' must be callable")
 
         source = getStackFrame()
-        self._setup(doc=doc, dtype=List, default=default, check=None, optional=optional, source=source)
+        self._setup(doc=doc, dtype=List, default=default, check=None, optional=optional, source=source,
+                    deprecated=deprecated)
 
         self.listCheck = listCheck
         """Callable used to check the list as a whole.

python/lsst/pex/config/rangeField.py

@@ -53,6 +53,9 @@ class RangeField(Field):
     inclusiveMax : `bool`, optional
         If `True` (default), the ``max`` value is included in the allowed
         range.
+    deprecated : None or `str`, optional
+        A description of why this Field is deprecated, including removal date.
+        If not None, the string is appended to the docstring for this Field.
 
     See also
     --------
@@ -73,7 +76,8 @@ class RangeField(Field):
     """
 
     def __init__(self, doc, dtype, default=None, optional=False,
-                 min=None, max=None, inclusiveMin=True, inclusiveMax=False):
+                 min=None, max=None, inclusiveMin=True, inclusiveMax=False,
+                 deprecated=None):
         if dtype not in self.supportedTypes:
             raise ValueError("Unsupported RangeField dtype %s" % (_typeStr(dtype)))
         source = getStackFrame()
@@ -104,7 +108,8 @@ def __init__(self, doc, dtype, default=None, optional=False,
             self.minCheck = lambda x, y: True if y is None else x >= y
         else:
             self.minCheck = lambda x, y: True if y is None else x > y
-        self._setup(doc, dtype=dtype, default=default, check=None, optional=optional, source=source)
+        self._setup(doc, dtype=dtype, default=default, check=None, optional=optional, source=source,
+                    deprecated=deprecated)
         self.rangeString = "%s%s,%s%s" % \
             (("[" if inclusiveMin else "("),
              ("-inf" if self.min is None else self.min),

tests/test_Config.py

@@ -26,10 +26,11 @@
 import itertools
 import re
 import os
+import pickle
 import unittest
+
 import lsst.utils.tests
 import lsst.pex.config as pexConfig
-import pickle
 
 GLOBAL_REGISTRY = {}
 
@@ -80,12 +81,17 @@ class Complex(pexConfig.Config):
                                     default="BBB", optional=True)
 
 
+class Deprecation(pexConfig.Config):
+    old = pexConfig.Field("Something.", int, default=10, deprecated="not used!")
+
+
 class ConfigTest(unittest.TestCase):
     def setUp(self):
         self.simple = Simple()
         self.inner = InnerConfig()
         self.outer = OuterConfig()
         self.comp = Complex()
+        self.deprecation = Deprecation()
 
     def tearDown(self):
         del self.simple
@@ -101,6 +107,9 @@ def testInit(self):
         self.assertEqual(list(self.simple.ll), [1, 2, 3])
         self.assertEqual(self.simple.d["key"], "value")
         self.assertEqual(self.inner.f, 0.0)
+        self.assertEqual(self.deprecation.old, 10)
+
+        self.assertEqual(self.deprecation._fields['old'].doc, "Something. Deprecated: not used!")
 
         self.assertEqual(self.outer.i.f, 5.0)
         self.assertEqual(self.outer.f, 0.0)
@@ -110,6 +119,15 @@ def testInit(self):
         self.assertEqual(self.comp.r.active.f, 3.0)
         self.assertEqual(self.comp.r["BBB"].f, 0.0)
 
+    def testDeprecationWarning(self):
+        """Test that a deprecated field emits a warning when it is set.
+        """
+        with self.assertWarns(FutureWarning) as w:
+            self.deprecation.old = 5
+            self.assertEqual(self.deprecation.old, 5)
+
+            self.assertIn(self.deprecation._fields['old'].deprecated, str(w.warnings[-1].message))
+
     def testValidate(self):
         self.simple.validate()