1 files changed, 71 insertions, 0 deletions
diff --git a/python/py/py/_io/saferepr.py b/python/py/py/_io/saferepr.py
new file mode 100644
index 000000000..8518290ef
--- /dev/null
+++ b/python/py/py/_io/saferepr.py
@@ -0,0 +1,71 @@
+import py
+import sys
+
+builtin_repr = repr
+
+reprlib = py.builtin._tryimport('repr', 'reprlib')
+
+class SafeRepr(reprlib.Repr):
+    """ subclass of repr.Repr that limits the resulting size of repr()
+        and includes information on exceptions raised during the call.
+    """
+    def repr(self, x):
+        return self._callhelper(reprlib.Repr.repr, self, x)
+
+    def repr_unicode(self, x, level):
+        # Strictly speaking wrong on narrow builds
+        def repr(u):
+            if "'" not in u:
+                return py.builtin._totext("'%s'") % u
+            elif '"' not in u:
+                return py.builtin._totext('"%s"') % u
+            else:
+                return py.builtin._totext("'%s'") % u.replace("'", r"\'")
+        s = repr(x[:self.maxstring])
+        if len(s) > self.maxstring:
+            i = max(0, (self.maxstring-3)//2)
+            j = max(0, self.maxstring-3-i)
+            s = repr(x[:i] + x[len(x)-j:])
+            s = s[:i] + '...' + s[len(s)-j:]
+        return s
+
+    def repr_instance(self, x, level):
+        return self._callhelper(builtin_repr, x)
+
+    def _callhelper(self, call, x, *args):
+        try:
+            # Try the vanilla repr and make sure that the result is a string
+            s = call(x, *args)
+        except py.builtin._sysex:
+            raise
+        except:
+            cls, e, tb = sys.exc_info()
+            exc_name = getattr(cls, '__name__', 'unknown')
+            try:
+                exc_info = str(e)
+            except py.builtin._sysex:
+                raise
+            except:
+                exc_info = 'unknown'
+            return '<[%s("%s") raised in repr()] %s object at 0x%x>' % (
+                exc_name, exc_info, x.__class__.__name__, id(x))
+        else:
+            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
+
+def saferepr(obj, maxsize=240):
+    """ return a size-limited safe repr-string for the given object.
+    Failing __repr__ functions of user instances will be represented
+    with a short exception info and 'saferepr' generally takes
+    care to never raise exceptions itself.  This function is a wrapper
+    around the Repr/reprlib functionality of the standard 2.6 lib.
+    """
+    # review exception handling
+    srepr = SafeRepr()
+    srepr.maxstring = maxsize
+    srepr.maxsize = maxsize
+    srepr.maxother = 160
+    return srepr.repr(obj)