Detect failures to explicitly close mmaps in py3 too

[bup.git] / lib / bup / compat.py

diff --git a/lib/bup/compat.py b/lib/bup/compat.py
index a06ffe8ee581d9cab13e1764740241768d2d2210..00575036e27cc46f7fb6b3408e273831526b9daa 100644 (file)
--- a/lib/bup/compat.py
+++ b/lib/bup/compat.py
@@ -1,6 +1,5 @@
 
 from __future__ import absolute_import, print_function
-from array import array
 from binascii import hexlify
 from traceback import print_exception
 import os, sys
@@ -13,9 +12,13 @@ py3 = py_maj >= 3
 
 if py3:
 
+    # pylint: disable=unused-import
+    from contextlib import ExitStack, nullcontext
     from os import environb as environ
     from os import fsdecode, fsencode
     from shlex import quote
+    # pylint: disable=undefined-variable
+    # (for python2 looking here)
     ModuleNotFoundError = ModuleNotFoundError
     input = input
     range = range
@@ -38,18 +41,23 @@ if py3:
         return ex
 
     class pending_raise:
-        """Rethrow either the provided ex, or any exception raised by the with
-        statement body.  (Supports Python 2 compatibility.)
+        """If rethrow is true, rethrow ex (if any), unless the body throws.
+
+        (Supports Python 2 compatibility.)
 
         """
-        def __init__(self, ex):
+        def __init__(self, ex, rethrow=True):
+            self.closed = False
             self.ex = ex
+            self.rethrow = rethrow
         def __enter__(self):
             return None
         def __exit__(self, exc_type, exc_value, traceback):
-            if not exc_type:
+            self.closed = True
+            if not exc_type and self.ex and self.rethrow:
                 raise self.ex
-            return None
+        def __del__(self):
+            assert self.closed
 
     def items(x):
         return x.items()
@@ -79,6 +87,8 @@ if py3:
 
 else:  # Python 2
 
+    from contextlib import contextmanager
+
     ModuleNotFoundError = ImportError
 
     def fsdecode(x):
@@ -88,13 +98,24 @@ else:  # Python 2
         return x
 
     from pipes import quote
+    # pylint: disable=unused-import
     from os import environ, getcwd
 
+    # pylint: disable=unused-import
     from bup.py2raise import reraise
 
+    @contextmanager
+    def nullcontext(enter_result=None):
+        yield enter_result
+
+    # on py3 this causes errors, obviously
+    # pylint: disable=undefined-variable
     input = raw_input
+    # pylint: disable=undefined-variable
     range = xrange
+    # pylint: disable=undefined-variable
     str_type = basestring
+    # pylint: disable=undefined-variable
     int_types = (int, long)
 
     hexstr = hexlify
@@ -118,24 +139,32 @@ else:  # Python 2
         return ex
 
     class pending_raise:
-        """Rethrow either the provided ex, or any exception raised by the with
-        statement body, after making ex the __context__ of the newer
-        exception (assuming there's no existing __context__).  Ensure
-        the exceptions have __tracebacks__.  (Supports Python 2
-        compatibility.)
+        """If rethrow is true, rethrow ex (if any), unless the body throws.
+
+        If the body does throw, make any provided ex the __context__
+        of the newer exception (assuming there's no existing
+        __context__).  Ensure the exceptions have __tracebacks__.
+        (Supports Python 2 compatibility.)
 
         """
-        def __init__(self, ex):
+        def __init__(self, ex, rethrow=True):
+            self.closed = False
             self.ex = ex
+            self.rethrow = rethrow
         def __enter__(self):
-            add_ex_tb(self.ex)
-            return None
+            if self.ex:
+                add_ex_tb(self.ex)
         def __exit__(self, exc_type, exc_value, traceback):
-            if not exc_type:
+            self.closed = True
+            if exc_value:
+                if self.ex:
+                    add_ex_tb(exc_value)
+                    add_ex_ctx(exc_value, self.ex)
+                return
+            if self.rethrow and self.ex:
                 raise self.ex
-            add_ex_tb(exc_value)
-            add_ex_ctx(exc_value, self.ex)
-            return None
+        def __del__(self):
+            assert self.closed
 
     def dump_traceback(ex):
         stack = [ex]
@@ -153,6 +182,31 @@ else:  # Python 2
             tb = getattr(ex, '__traceback__', None)
             print_exception(type(ex), ex, tb)
 
+    class ExitStack:
+        def __init__(self):
+            self.contexts = []
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, value_type, value, traceback):
+            init_value = value
+            for ctx in reversed(self.contexts):
+                try:
+                    ctx.__exit__(value_type, value, traceback)
+                except BaseException as ex:
+                    add_ex_tb(ex)
+                    if value:
+                        add_ex_ctx(ex, value)
+                    value_type = type(ex)
+                    value = ex
+                    traceback = ex.__traceback__
+            if value is not init_value:
+                raise value
+
+        def enter_context(self, x):
+            self.contexts.append(x)
+
     def items(x):
         return x.iteritems()