Merge pull request #4148 from HypothesisWorks/DRMacIver/use-provided-…

…pretty

Always use a repr_pretty if provided

hypothesis-python/RELEASE.rst

@@ -0,0 +1,5 @@
+RELEASE_TYPE: patch
+
+This patch changes the priority order of pretty printing logic so that a user
+provided pretty printing method will always be used in preference to e.g.
+printing it like a dataclass.

hypothesis-python/src/hypothesis/vendor/pretty.py

@@ -186,6 +186,16 @@ def pretty(self, obj):
                     pass
                 else:
                     return printer(obj, self, cycle)
+
+                # Look for the _repr_pretty_ method which allows users
+                # to define custom pretty printing.
+                # Some objects automatically create any requested
+                # attribute. Try to ignore most of them by checking for
+                # callability.
+                pretty_method = _safe_getattr(obj, "_repr_pretty_", None)
+                if callable(pretty_method):
+                    return pretty_method(self, cycle)
+
                 # Next walk the mro and check for either:
                 #   1) a registered printer
                 #   2) a _repr_pretty_ method
@@ -206,14 +216,6 @@ def pretty(self, obj):
                             self.type_pprinters[cls] = printer
                             return printer(obj, self, cycle)
                         else:
-                            # Finally look for special method names.
-                            # Some objects automatically create any requested
-                            # attribute. Try to ignore most of them by checking for
-                            # callability.
-                            if "_repr_pretty_" in cls.__dict__:
-                                meth = cls._repr_pretty_
-                                if callable(meth):
-                                    return meth(obj, self, cycle)
                             if hasattr(cls, "__attrs_attrs__"):
                                 return pprint_fields(
                                     obj,

hypothesis-python/tests/cover/test_pretty.py

@@ -47,6 +47,7 @@
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 """
 
+import io
 import re
 import struct
 import sys
@@ -100,9 +101,12 @@ def _repr_pretty_(self, p, cycle):
         p.text("Dummy1(...)")
 
 
-class Dummy2(Dummy1):
+class Dummy2:
     _repr_pretty_ = None
 
+    def __repr__(self):
+        return "Dummy2()"
+
 
 class NoModule:
     pass
@@ -207,7 +211,7 @@ def test_callability_checking():
     """Test that the _repr_pretty_ method is tested for callability and skipped
     if not."""
     gotoutput = pretty.pretty(Dummy2())
-    expectedoutput = "Dummy1(...)"
+    expectedoutput = "Dummy2()"
 
     assert gotoutput == expectedoutput
 
@@ -901,3 +905,29 @@ class E(Enum):
 @pytest.mark.parametrize("obj", NAMESPACED_VALUES, ids=map(repr, NAMESPACED_VALUES))
 def test_includes_namespace_classes_in_pretty(obj):
     assert pretty.pretty(obj).startswith("Namespace.")
+
+
+class Banana:
+    def _repr_pretty_(self, p, cycle):
+        p.text("I am a banana")
+
+
+@dataclass
+class InheritsPretty(Banana):
+    x: int
+    y: int
+
+
+def test_uses_defined_pretty_printing_method():
+    assert pretty.pretty(InheritsPretty(x=1, y=2)) == pretty.pretty(Banana())
+
+
+def test_prefers_singleton_printing_to_repr_pretty():
+    out = io.StringIO()
+    printer = pretty.RepresentationPrinter(out)
+    banana = Banana()
+    printer.singleton_pprinters[id(banana)] = lambda obj, p, cycle: p.text(
+        "Actually a fish"
+    )
+    printer.pretty(banana)
+    assert "Actually a fish" in out.getvalue()