Fix TerminalRepr instances to be hashable (#6988)

pytest-xdist assumes `ExceptionChainRepr` is hashable.

Fixes https://github.com/pytest-dev/pytest/issues/6925.
Fixes https://github.com/pytest-dev/pytest-xdist/issues/515.

changelog/6925.bugfix.rst

@@ -0,0 +1 @@
+Fix TerminalRepr instances to be hashable again.

src/_pytest/_code/code.py

@@ -32,6 +32,7 @@ import _pytest
 from _pytest._io import TerminalWriter
 from _pytest._io.saferepr import safeformat
 from _pytest._io.saferepr import saferepr
+from _pytest.compat import ATTRS_EQ_FIELD
 from _pytest.compat import overload
 from _pytest.compat import TYPE_CHECKING
 
@@ -911,7 +912,7 @@ class FormattedExcinfo:
         return ExceptionChainRepr(repr_chain)
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class TerminalRepr:
     def __str__(self) -> str:
         # FYI this is called from pytest-xdist's serialization of exception
@@ -928,7 +929,7 @@ class TerminalRepr:
         raise NotImplementedError()
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ExceptionRepr(TerminalRepr):
     def __attrs_post_init__(self):
         self.sections = []  # type: List[Tuple[str, str, str]]
@@ -942,7 +943,7 @@ class ExceptionRepr(TerminalRepr):
             tw.line(content)
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ExceptionChainRepr(ExceptionRepr):
     chain = attr.ib(
         type=Sequence[
@@ -966,7 +967,7 @@ class ExceptionChainRepr(ExceptionRepr):
         super().toterminal(tw)
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprExceptionInfo(ExceptionRepr):
     reprtraceback = attr.ib(type="ReprTraceback")
     reprcrash = attr.ib(type="ReprFileLocation")
@@ -976,7 +977,7 @@ class ReprExceptionInfo(ExceptionRepr):
         super().toterminal(tw)
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprTraceback(TerminalRepr):
     reprentries = attr.ib(type=Sequence[Union["ReprEntry", "ReprEntryNative"]])
     extraline = attr.ib(type=Optional[str])
@@ -1010,7 +1011,7 @@ class ReprTracebackNative(ReprTraceback):
         self.extraline = None
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprEntryNative(TerminalRepr):
     lines = attr.ib(type=Sequence[str])
     style = "native"  # type: _TracebackStyle
@@ -1019,7 +1020,7 @@ class ReprEntryNative(TerminalRepr):
         tw.write("".join(self.lines))
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprEntry(TerminalRepr):
     lines = attr.ib(type=Sequence[str])
     reprfuncargs = attr.ib(type=Optional["ReprFuncArgs"])
@@ -1100,7 +1101,7 @@ class ReprEntry(TerminalRepr):
         )
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprFileLocation(TerminalRepr):
     path = attr.ib(type=str, converter=str)
     lineno = attr.ib(type=int)
@@ -1117,7 +1118,7 @@ class ReprFileLocation(TerminalRepr):
         tw.line(":{}: {}".format(self.lineno, msg))
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprLocals(TerminalRepr):
     lines = attr.ib(type=Sequence[str])
 
@@ -1126,7 +1127,7 @@ class ReprLocals(TerminalRepr):
             tw.line(indent + line)
 
 
-@attr.s
+@attr.s(**{ATTRS_EQ_FIELD: False})  # type: ignore
 class ReprFuncArgs(TerminalRepr):
     args = attr.ib(type=Sequence[Tuple[str, object]])
 

testing/code/test_code.py

@@ -6,6 +6,7 @@ import pytest
 from _pytest._code import Code
 from _pytest._code import ExceptionInfo
 from _pytest._code import Frame
+from _pytest._code.code import ExceptionChainRepr
 from _pytest._code.code import ReprFuncArgs
 
 
@@ -180,3 +181,20 @@ class TestReprFuncArgs:
             tw_mock.lines[0]
             == r"unicode_string = São Paulo, utf8_string = b'S\xc3\xa3o Paulo'"
         )
+
+
+def test_ExceptionChainRepr():
+    """Test ExceptionChainRepr, especially with regard to being hashable."""
+    try:
+        raise ValueError()
+    except ValueError:
+        excinfo1 = ExceptionInfo.from_current()
+        excinfo2 = ExceptionInfo.from_current()
+
+    repr1 = excinfo1.getrepr()
+    repr2 = excinfo2.getrepr()
+    assert repr1 != repr2
+
+    assert isinstance(repr1, ExceptionChainRepr)
+    assert hash(repr1) != hash(repr2)
+    assert repr1 is not excinfo1.getrepr()