[rspec-users] How do I get additional information from the Matcher?

David Chelimsky dchelimsky at gmail.com
Tue May 26 23:39:22 EDT 2009

On Wed, May 20, 2009 at 6:32 PM, Gary Lin <glin at employees.org> wrote:
> Hi,
> I am trying to implement my own matcher which use a special algorithm to do
> the semantics diff-ing between two proprietary configuration file.  When
> come to the report, I would like my formatter to be able to have access to
> the original configuration file content as well as the diff-ing result.  By
> digging through the code, looks like all formatter can get is an
> ExpectationNotMetError with a string-based message embedded inside.  How do
> I make the matcher pass additional information to my formatter?  I see there
> is a class level variable called ::Spec::Matchers.last_matcher which allows
> me to access the last matcher.  Is that the right away to implement this?
>  Or if there is any better way for me to add additional information into the
> ExpectationNotMetError exception?

There's nothing built in. If you have any recommendations as to how
this should work, please feel free to file a feature request at


> Thanks,
> --Gary
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