MetaStoreWriter.__del__: replace with context management

[bup.git] / CODINGSTYLE

diff --git a/CODINGSTYLE b/CODINGSTYLE
index 1bc76fadfb09cfabc548cf0cc6e33387848f7030..348a2f51340bfe3545b7f9477cde631343126e7c 100644 (file)
--- a/CODINGSTYLE
+++ b/CODINGSTYLE
@@ -43,7 +43,6 @@ explicitly add stack traces to any exceptions that are going to be
 re-raised by anything other than a no-argument raise (otherwise the
 stack trace will be lost)::
 
-
   try:
       ...
   except ... as ex:
@@ -52,9 +51,24 @@ stack trace will be lost)::
   ...
   raise pending_ex
 
-If an exception is thrown from an exception handler, the pending
-exception should be "chained" to the new exception as the context.
-This can be accomplished via ``chain_ex()``::
+When an exception is thrown from an exception handler, the pending
+exception should be the `"context"
+<https://docs.python.org/3/reference/simple_stmts.html#the-raise-statement>`_
+of the new exception, which can be accomplished (portably) via
+``pending_raise()``::
+
+  try:
+      ...
+  except ... as ex:
+      with pending_raise(ex):
+          clean_up()
+
+This should do roughly the same thing in Python 2 and Python 3,
+throwing any exception from ``clean_up()`` after adding ex as the
+``__context__`` if clean_up() throws, and throwing ``ex`` otherwise.
+
+If for some reason, you need more control, you can use
+``add_ex_ctx()`` directly::
 
   try:
       ...
@@ -64,6 +78,8 @@ This can be accomplished via ``chain_ex()``::
           ...
       except ... as ex2:
           add_ex_tb(ex2)
-          raise chain_ex(ex2, ex)
+          raise add_ex_ctx(ex2, ex)
+      raise
 
-See the end of ``lib/bup/compat.py`` for a functional example.
+See the end of ``lib/bup/compat.py`` for a functional example, and all
+of this can be removed once we drop support for Python 2.