WIP: assert: use safeformat for display with -vv

TODO:

- [ ] real plugin hook?
- [ ] should handle other places where safeformat is used also, via
      args/options to the hook then likely.

Ref: pytest-dev#3962
Ref: pytest-dev#5933

src/_pytest/assertion/__init__.py

@@ -141,6 +141,17 @@ def callbinrepr(op, left, right):
 
     util._reprcompare = callbinrepr
 
+    from _pytest._io.saferepr import safeformat
+    from _pytest._io.saferepr import saferepr
+
+    def call_assertion_display_hook(obj):
+        verbose = item.config.getoption("verbose")
+        if verbose > 1:
+            return safeformat(obj)
+        return saferepr(obj).replace("\n", "\\n")
+
+    util._reprdisplay = call_assertion_display_hook
+
     if item.ihook.pytest_assertion_pass.get_hookimpls():
 
         def call_assertion_pass_hook(lineno, orig, expl):
@@ -153,6 +164,7 @@ def call_assertion_pass_hook(lineno, orig, expl):
 
 def pytest_runtest_teardown(item):
     util._reprcompare = None
+    util._reprdisplay = None
     util._assertion_pass = None
 
 

src/_pytest/assertion/rewrite.py

@@ -398,6 +398,10 @@ def _call_reprcompare(ops, results, expls, each_obj):
     return expl
 
 
+def _call_reprdisplay(obj):
+    return util._reprdisplay(obj)
+
+
 def _call_assertion_pass(lineno, orig, expl):
     # type: (int, str, str) -> None
     if util._assertion_pass is not None:
@@ -662,8 +666,7 @@ def assign(self, expr):
         return ast.Name(name, ast.Load())
 
     def display(self, expr):
-        """Call saferepr on the expression."""
-        return self.helper("_saferepr", expr)
+        return self.helper("_call_reprdisplay", expr)
 
     def helper(self, name, *args):
         """Call a helper in this module."""