From 9a63df4e774e517918ae944dbc89e8b2bac17568 Mon Sep 17 00:00:00 2001
From: Matthias Diener <mdiener@illinois.edu>
Date: Sun, 17 Sep 2023 18:55:14 -0500
Subject: [PATCH] remove __eq__ function, more eq testing

---
 grudge/trace_pair.py    |  3 --
 test/test_trace_pair.py | 68 +++++++++++++++++++++++++++++++++++------
 2 files changed, 58 insertions(+), 13 deletions(-)

diff --git a/grudge/trace_pair.py b/grudge/trace_pair.py
index a9803bf43..d2f8aeb0b 100644
--- a/grudge/trace_pair.py
+++ b/grudge/trace_pair.py
@@ -327,9 +327,6 @@ class CommTag:
     def __hash__(self):
         return hash(tuple(str(type(self)).encode("ascii")))
 
-    def __eq__(self, other):
-        return isinstance(other, type(self))
-
 
 def interior_trace_pairs(dcoll: DiscretizationCollection, vec, *,
         comm_tag: Optional[Hashable] = None, tag: Hashable = None,
diff --git a/test/test_trace_pair.py b/test/test_trace_pair.py
index ce84eba48..9e26032c4 100644
--- a/test/test_trace_pair.py
+++ b/test/test_trace_pair.py
@@ -25,6 +25,7 @@
 from grudge.trace_pair import TracePair, CommTag
 import meshmode.mesh.generation as mgen
 from meshmode.dof_array import DOFArray
+from dataclasses import dataclass
 
 from grudge import DiscretizationCollection
 
@@ -74,15 +75,62 @@ def test_commtag(actx_factory):
     class DerivedCommTag(CommTag):
         pass
 
-    x = CommTag()
-    x2 = CommTag()
-    y = DerivedCommTag()
+    class DerivedDerivedCommTag(DerivedCommTag):
+        pass
+
+    # {{{ test equality and hash consistency
+
+    ct = CommTag()
+    ct2 = CommTag()
+    dct = DerivedCommTag()
+    dct2 = DerivedCommTag()
+    ddct = DerivedDerivedCommTag()
+
+    assert ct == ct2
+    assert ct != dct
+    assert dct == dct2
+    assert dct != ddct
+    assert ddct != dct
+    assert (ct, dct) != (dct, ct)
+
+    assert hash(ct) == hash(ct2)
+    assert hash(ct) != hash(dct)
+    assert hash(dct) != hash(ddct)
+
+    # }}}
+
+    # {{{ test hash stability
+
+    assert hash(ct) == 4644528671524962420
+    assert hash(dct) == -1013583671995716582
+    assert hash(ddct) == 626392264874077479
+
+    assert hash((ct, 123)) == -578844573019921397
+    assert hash((dct, 123)) == -8009406276367324841
+    assert hash((dct, ct)) == 6599529611285265043
+
+    # }}}
+
+    # {{{ test using derived dataclasses
+
+    @dataclass(frozen=True)
+    class DataCommTag(CommTag):
+        data: int
+
+    @dataclass(frozen=True)
+    class DataCommTag2(CommTag):
+        data: int
+
+    d1 = DataCommTag(1)
+    d2 = DataCommTag(2)
+    d3 = DataCommTag(1)
+
+    assert d1 != d2
+    assert hash(d1) != hash(d2)
+    assert d1 == d3
+    assert hash(d1) == hash(d3)
 
-    assert hash(x) == hash(x2)
-    assert hash(x) != hash(y)
-    assert hash(x) == 4644528671524962420
-    assert hash(y) == -1013583671995716582
+    d4 = DataCommTag2(1)
+    assert d1 != d4
 
-    assert hash((x, 123)) == -578844573019921397
-    assert hash((y, 123)) == -8009406276367324841
-    assert hash((y, x)) == 6599529611285265043
+    # }}}