Merge pull request #28 from zodb/issue26

Add support for hamcrest 1.10 and above.

CHANGES.rst

@@ -7,7 +7,8 @@
 
 - Add support for Python 3.8 and 3.9.
 - Move to GitHub Actions from Travis CI.
-
+- Support PyHamcrest 1.10 and later. See `issue 26
+  <https://github.com/zodb/perfmetrics/issues/26>`_.
 
 3.0.0 (2019-09-03)
 ==================

setup.py

@@ -17,7 +17,7 @@ def read(fname, here=os.path.dirname(__file__)):
 tests_require = [
     'zope.testrunner',
     'nti.testing',
-    'pyhamcrest < 1.10',
+    'pyhamcrest >= 1.10',
     'pyperf',
 ]
 

src/perfmetrics/testing/matchers.py

@@ -13,6 +13,7 @@
 from hamcrest import has_properties
 from hamcrest import none
 
+
 from .observation import OBSERVATION_KIND_COUNTER as METRIC_COUNTER_KIND
 from .observation import OBSERVATION_KIND_GAUGE as METRIC_GAUGE_KIND
 from .observation import OBSERVATION_KIND_SET as METRIC_SET_KIND
@@ -37,8 +38,12 @@
     's': 'set'
 }
 
+
 class IsMetric(BaseMatcher):
 
+    # See _matches()
+    _force_one_description = False
+
     def __init__(self, kwargs):
         matchers = {}
         for key, value in kwargs.items():
@@ -52,13 +57,39 @@ def __init__(self, kwargs):
                 value = str(value)
             matchers[key] = value
 
+        # Beginning in 1.10 and up through at least 2.0.2,
+        # has_properties con no longer be called with an empty dictionary
+        # without creating a KeyError from popitem().
         self._matcher = all_of(
             instance_of(Observation),
-            has_properties(**matchers)
+            has_properties(**matchers) if matchers else instance_of(Observation),
         )
+        if self._force_one_description:
+            self.__patch_matcher()
+
+    def __patch_matcher(self):
+        # This is tightly coupled to the structure of the matcher we create.
+        self._matcher.describe_all_mismatches = False
+        has_prop_matcher = self._matcher.matchers[1]
+        if hasattr(has_prop_matcher, 'matcher'):
+            has_prop_matcher.matcher.describe_all_mismatches = False
 
     def _matches(self, item):
-        return self._matcher.matches(item)
+        # On PyHamcrest == 1.10.x (last release for Python 2)
+        # There's a bug such that you can't call AllOf.matches without
+        # passing in a description without getting
+        # ``AttributeError: None has no append_text``
+        # So we pass one, even though it gets thrown away.
+        # XXX: Remove this workaround when we only support PyHamcrest 2.
+        # See https://github.com/hamcrest/PyHamcrest/issues/130
+        try:
+            return self._matcher.matches(item)
+        except AttributeError as ex:
+            if 'append_text' not in str(ex): # pragma: no cover
+                raise
+            IsMetric._force_one_description = True
+            self.__patch_matcher()
+            return self._matcher.matches(item)
 
     def describe_to(self, description):
         self._matcher.describe_to(description)

src/perfmetrics/testing/tests/test_matchers.py

@@ -70,19 +70,29 @@ def test_failure_error(self):
         matcher = is_counter('foo', '1', 0.1)
         matcher.describe_to(desc)
         desc = str(desc)
+        # Strip internal newlines, which vary between
+        # hamcrest versions. Also, the exact text varies too;
+        # beginning with 1.10, the has_properties matcher we use internally is
+        # less verbose by default and so we get a string like:
+        #   an object with properties kind matching c and name matching foo
+        # where before it was something like
+        #  an object with property kind matching c
+        #  and an object with property name matching foo
+
+        desc = desc.replace('\n', '')
         assert_that(
             desc,
             all_of(
                 contains_string(
                     "(an instance of Observation and "),
                 contains_string(
-                    "an object with a property 'kind' matching 'c'"),
+                    "'kind' matching 'c'"),
                 contains_string(
-                    "an object with a property 'name' matching 'foo'"),
+                    "'name' matching 'foo'"),
                 contains_string(
-                    "an object with a property 'value' matching '1'"),
+                    "'value' matching '1'"),
                 contains_string(
-                    "an object with a property 'sampling_rate' matching <0.1>"
+                    "'sampling_rate' matching <0.1>"
                 )
             )
         )