minor: move internal _pformat_dispatch function

src/_pytest/_io/saferepr.py

@@ -80,3 +80,24 @@ def saferepr(obj: Any, maxsize: int = 240) -> str:
     around the Repr/reprlib functionality of the standard 2.6 lib.
     """
     return SafeRepr(maxsize).repr(obj)
+
+
+class AlwaysDispatchingPrettyPrinter(pprint.PrettyPrinter):
+    """PrettyPrinter that always dispatches (regardless of width)."""
+
+    def _format(self, object, stream, indent, allowance, context, level):
+        p = self._dispatch.get(type(object).__repr__, None)
+
+        objid = id(object)
+        if objid in context or p is None:
+            return super()._format(object, stream, indent, allowance, context, level)
+
+        context[objid] = 1
+        p(self, object, stream, indent, allowance, context, level + 1)
+        del context[objid]
+
+
+def _pformat_dispatch(object, indent=1, width=80, depth=None, *, compact=False):
+    return AlwaysDispatchingPrettyPrinter(
+        indent=1, width=80, depth=None, compact=False
+    ).pformat(object)

src/_pytest/assertion/util.py

@@ -13,6 +13,7 @@
 
 import _pytest._code
 from _pytest import outcomes
+from _pytest._io.saferepr import _pformat_dispatch
 from _pytest._io.saferepr import safeformat
 from _pytest._io.saferepr import saferepr
 from _pytest.compat import ATTRS_EQ_FIELD
@@ -28,27 +29,6 @@
 _assertion_pass = None  # type: Optional[Callable[[int, str, str], None]]
 
 
-class AlwaysDispatchingPrettyPrinter(pprint.PrettyPrinter):
-    """PrettyPrinter that always dispatches (regardless of width)."""
-
-    def _format(self, object, stream, indent, allowance, context, level):
-        p = self._dispatch.get(type(object).__repr__, None)
-
-        objid = id(object)
-        if objid in context or p is None:
-            return super()._format(object, stream, indent, allowance, context, level)
-
-        context[objid] = 1
-        p(self, object, stream, indent, allowance, context, level + 1)
-        del context[objid]
-
-
-def _pformat_dispatch(object, indent=1, width=80, depth=None, *, compact=False):
-    return AlwaysDispatchingPrettyPrinter(
-        indent=1, width=80, depth=None, compact=False
-    ).pformat(object)
-
-
 def format_explanation(explanation: str) -> str:
     """This formats an explanation