This patch preserves more of the information carried by exceptions that
bubble up from particular database libraries and are handled by sequel,
so that you don't have to parse and match message strings.
The basic idea, abstracted from Sequel, is this:
class DatabaseError < StandardError; end
def raise_error(ex)
raise DatabaseError, ex, ex.backtrace
end
def foo
raise ArgumentError, "bad args"
rescue => ex
raise_error(ex)
end
begin
foo
rescue => ex
puts "CLASS:"
puts ex.message.class # ==> ArgumentError
puts "MESSAGE:"
puts ex.message # ==> bad args
puts "AS RAISED:"
raise # raise_error.rb:8:in `foo': bad args
(DatabaseError)
# from raise_error.rb:14
end
This uses two tricks in ruby exception handling:
1. The message can be any object.
2. The third argument to raise can be a backtrace (that's not important
for this exercise, though).
Note that the default output of raise doesn't show the wrapped exception
class, but you can easily get it displayed using message.inspect or
message.class.
The value of this, IMO, is that you can do
case ex.message
when SomeWrappedException
...
end
instead of having to parse the message string.
This works as a monkey patch, or as the patch below. It will break code
if the code was written to depend on message strings having certain
contents (which is probably a bad idea anyway).
---
sequel-3.3.0/lib/sequel/database.rb 2009-08-03 10:06:28.000000000 -0700
+++ - 2009-09-01 08:40:08.340063788 -0700
@@ -792,7 +792,7 @@
# and traceback.
def raise_error(exception, opts={})
if !opts[:classes] || Array(opts[:classes]).any?{|c|
exception.is_a?(c)}
- e = (opts[:disconnect] ? DatabaseDisconnectError :
DatabaseError).new("#{exception.class}: #{exception.message}")
+ e = (opts[:disconnect] ? DatabaseDisconnectError :
DatabaseError).new(exception)
e.set_backtrace(exception.backtrace)
raise e
else
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
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