saferepr: Avoid indirect function calls

The DRY savings they provide are rather small, while they make it harder
to type-check, and IMO harder to understand.

Author: bluetech

changelog/5603.trivial.rst

@@ -0,0 +1 @@
+Simplified internal ``SafeRepr`` class and removed some dead code.

src/_pytest/_io/saferepr.py

@@ -2,19 +2,23 @@
 import reprlib
 
 
-def _call_and_format_exception(call, x, *args):
+def _format_repr_exception(exc, obj):
+    exc_name = type(exc).__name__
     try:
-        # Try the vanilla repr and make sure that the result is a string
-        return call(x, *args)
-    except Exception as exc:
-        exc_name = type(exc).__name__
-        try:
-            exc_info = str(exc)
-        except Exception:
-            exc_info = "unknown"
-        return '<[{}("{}") raised in repr()] {} object at 0x{:x}>'.format(
-            exc_name, exc_info, x.__class__.__name__, id(x)
-        )
+        exc_info = str(exc)
+    except Exception:
+        exc_info = "unknown"
+    return '<[{}("{}") raised in repr()] {} object at 0x{:x}>'.format(
+        exc_name, exc_info, obj.__class__.__name__, id(obj)
+    )
+
+
+def _ellipsize(s, maxsize):
+    if len(s) > maxsize:
+        i = max(0, (maxsize - 3) // 2)
+        j = max(0, maxsize - 3 - i)
+        return s[:i] + "..." + s[len(s) - j :]
+    return s
 
 
 class SafeRepr(reprlib.Repr):
@@ -28,26 +32,29 @@ def __init__(self, maxsize):
         self.maxsize = maxsize
 
     def repr(self, x):
-        return self._callhelper(reprlib.Repr.repr, self, x)
+        try:
+            s = super().repr(x)
+        except Exception as exc:
+            s = _format_repr_exception(exc, x)
+        return _ellipsize(s, self.maxsize)
 
     def repr_instance(self, x, level):
-        return self._callhelper(repr, x)
-
-    def _callhelper(self, call, x, *args):
-        s = _call_and_format_exception(call, x, *args)
-        if len(s) > self.maxsize:
-            i = max(0, (self.maxsize - 3) // 2)
-            j = max(0, self.maxsize - 3 - i)
-            s = s[:i] + "..." + s[len(s) - j :]
-        return s
+        try:
+            s = repr(x)
+        except Exception as exc:
+            s = _format_repr_exception(exc, x)
+        return _ellipsize(s, self.maxsize)
 
 
 def safeformat(obj):
     """return a pretty printed string for the given object.
     Failing __repr__ functions of user instances will be represented
     with a short exception info.
     """
-    return _call_and_format_exception(pprint.pformat, obj)
+    try:
+        return pprint.pformat(obj)
+    except Exception as exc:
+        return _format_repr_exception(exc, obj)
 
 
 def saferepr(obj, maxsize=240):

testing/io/test_saferepr.py

@@ -45,6 +45,17 @@ class BrokenReprException(Exception):
     assert "unknown" in s2
 
 
+def test_buggy_builtin_repr():
+    # Simulate a case where a repr for a builtin raises.
+    # reprlib dispatches by type name, so use "int".
+
+    class int:
+        def __repr__(self):
+            raise ValueError("Buggy repr!")
+
+    assert "Buggy" in saferepr(int())
+
+
 def test_big_repr():
     from _pytest._io.saferepr import SafeRepr