Merge ~cjwatson/lazr.restful:deprecate-safe-hasattr into lazr.restful:main

[Colin Watson]

Deprecate safe_hasattr

It's no longer needed now that `hasattr` only catches `AttributeError`. See https://docs.python.org/3/whatsnew/3.2.html#other-language-changes.

[Guruprasad (lgp171188)]

These changes are straightforward and look good to me. 👍

review: Approve

diff --git a/NEWS.rst b/NEWS.rst
index a909598..6e42cce 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -25,6 +25,8 @@ NEWS for lazr.restful
   cannot work on Python 3.  Use the class decorators
   ``@exported_as_webservice_entry`` and
   ``@exported_as_webservice_collection`` instead.
+- Deprecate ``lazr.restful.utils.safe_hasattr``, since Python's builtin
+  ``hasattr`` is fixed as of Python 3.2.
 
 1.1.0 (2021-10-07)
 ==================
diff --git a/src/lazr/restful/docs/utils.rst b/src/lazr/restful/docs/utils.rst
index ea1636a..525473e 100644
--- a/src/lazr/restful/docs/utils.rst
+++ b/src/lazr/restful/docs/utils.rst
@@ -300,6 +300,7 @@ makes problems harder to diagnose.
 (The builtin hasattr() is fixed as of Python 3.2.)
 
     >>> import sys
+    >>> import warnings
     >>> from lazr.restful.utils import safe_hasattr
 
     >>> class Oracle:
@@ -307,26 +308,28 @@ makes problems harder to diagnose.
     ...     def is_full_moon(self):
     ...         return full_moon
     >>> oracle = Oracle()
-    >>> if sys.version_info[:2] < (3, 2):
-    ...     hasattr(oracle, 'is_full_moon')
-    ... else:
-    ...     False
-    False
-    >>> safe_hasattr(oracle, 'is_full_moon')
+    >>> with warnings.catch_warnings(record=True):
+    ...     safe_hasattr(oracle, 'is_full_moon')
     Traceback (most recent call last):
       ...
-    NameError: ...name 'full_moon' is not defined
+    NameError: name 'full_moon' is not defined
 
     >>> full_moon = True
     >>> hasattr(oracle, 'is_full_moon')
     True
-    >>> safe_hasattr(oracle, 'is_full_moon')
+    >>> with warnings.catch_warnings(record=True) as warnings_log:
+    ...     safe_hasattr(oracle, 'is_full_moon')
     True
+    >>> print(warnings_log[0].message)
+    safe_hasattr is deprecated; use the hasattr builtin instead.
 
     >>> hasattr(oracle, 'weather')
     False
-    >>> safe_hasattr(oracle, 'weather')
+    >>> with warnings.catch_warnings(record=True) as warnings_log:
+    ...     safe_hasattr(oracle, 'weather')
     False
+    >>> print(warnings_log[0].message)
+    safe_hasattr is deprecated; use the hasattr builtin instead.
 
 smartquote()
 ============
diff --git a/src/lazr/restful/marshallers.py b/src/lazr/restful/marshallers.py
index e8b38fe..3279657 100644
--- a/src/lazr/restful/marshallers.py
+++ b/src/lazr/restful/marshallers.py
@@ -55,7 +55,6 @@ from lazr.restful.interfaces import (
     IServiceRootResource,
     IWebServiceConfiguration,
 )
-from lazr.restful.utils import safe_hasattr
 
 
 class URLDereferencingMixin:
@@ -310,7 +309,7 @@ class BytesFieldMarshaller(SimpleFieldMarshaller):
         """
         if value is None:
             return None
-        if safe_hasattr(value, "seek"):
+        if hasattr(value, "seek"):
             value.seek(0)
             value = value.read()
         elif not isinstance(value, (bytes, str)):
diff --git a/src/lazr/restful/utils.py b/src/lazr/restful/utils.py
index 2175977..244bfed 100644
--- a/src/lazr/restful/utils.py
+++ b/src/lazr/restful/utils.py
@@ -24,6 +24,7 @@ import operator
 import re
 import string
 import subprocess
+import warnings
 
 from zope.component import getUtility
 from zope.schema import getFieldsInOrder
@@ -357,8 +358,16 @@ def camelcase_to_underscore_separated(name):
 
 
 def safe_hasattr(ob, name):
-    """hasattr() that doesn't hide exceptions."""
-    return getattr(ob, name, missing) is not missing
+    """hasattr() that doesn't hide exceptions.
+
+    This is no longer useful in Python >= 3.2.
+    """
+    warnings.warn(
+        "safe_hasattr is deprecated; use the hasattr builtin instead.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    return hasattr(ob, name)
 
 
 def smartquote(str):