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Making ri useful

tyler@linux.com published on 01 September 2011

Update: I found out that this post was referenced in Episode 181 of The Ruby Show (around the 6 minute mark). Thanks for the link guys! (And no, the "R." is not for "Reverend" :) )


When I joined Lookout I made the transition from long-time Python developer, to Ruby noob. It wasn't a terrifically painful transition since the two languages are more alike than they are different, and I got assigned to a C project shortly after arriving.

One thing that had always bothered me, but not enough to fix it (since I was mostly working with C), was how obscenely frustrating it was to find documentation for methods/classes/modules/etc. Being habitual user of the Python REPL and its built in help() function, I was thrashing around like a sea turtle caught in a fishing net.

Earlier this week, after deciding that I had to fix this (lest I shoot myself), I noticed that somehow, someway, one of my RVM gemsets gave me useful output from the tool ri. I had become accustomed to ri not giving me useful information unless I had the full name of a class or method, e.g.:

-> % ri assert_raise
Nothing known about .assert_raise
-> %

Rubyists will recognize assert_raise as a method involved in the Test::Unit module (specifically it's mixed-in from Test::Unit::Assertions, which is another bucket of frustration for me), but up until recently my method of "documentation method resolution" had been to open a browser, pass a query to Google and pray that the method name wasn't too vague.

As it turns out, this is not the proper behavior for ri, something a Ruby novice like myself simply didn't know. In order to make ri useful, at least in versions under 1.9.2, you must install the rdoc-data gem and run a subsequent command:

-> % gem install rdoc rdoc-data
-> % rdoc-data --install

Having that gem installed, and having run rdoc-data --install all of a sudden turns that same ri command above into this:

-> % ri assert_raise

= .assert_raise

(from ruby core)
=== Implementation from Test::Unit::Assertions
------------------------------------------------------------------------------
assert_raise(*args) { || ... }

------------------------------------------------------------------------------

Passes if the block raises one of the given exceptions.

Example:
    assert_raise RuntimeError, LoadError do
        raise 'Boom!!!'
    end

-> %

All of a sudden, <Shift>-k when the cursor is over a symbol in Vim does something useful, all of a sudden I don't feel so completely and utterly lost when dealing with Ruby code, especially with methods being included from third party gems.

All of a sudden, I got really pissed that ri never informed me that I was operating in a completely dysfunctional state.

If nobody ever tells me that something is broken, how will I ever know to fix it?