Setting POS as an acronym makes action dispatch mangle POST type detection

[punchh]

We've set POS as an acronym inflection to reflect "Point Of Sale" in our project's inflections file. POS is a major entity in our application with a recent change.

However, post? method now fails because of

HTTP_METHOD_LOOKUP = Hash.new { |h, m| h[m] = m.underscore.to_sym if HTTP_METHODS.include?(m) }

https://github.com/rails/rails/blob/3-2-stable/actionpack/lib/action_dispatch/http/request.rb

I do not think that the above default Hash initializer in HTTP_METHOD_LOOKUP should be relying on underscore for converting to symbols and getting inflections from the project like the above get in the way of its conversion since the lookup to HTTP_METHODS has already returned TRUE.

The method now gets resolved as :pos_t. Ouch!

HTTP_METHOD_LOOKUP = Hash.new{ |h, m| h[m] = m.downcase.gsub(/-/,'_').to_sym if HTTP_METHODS.include?(m) }

The above works although i understand it's mildly less elegant but a lot safer considering the finite list to convert is just above this declaration in HTTP_METHODS.

Failing Test and Patch coming up.

cc @pixeltrix / @carlosantoniodasilva / @josevalim

[asanghi]

Just a note above that this problem would not appear on Rails 4 on the master branch because HTTP_METHOD_LOOKUP is eagerly setup when request.rb is loaded. Since this file gets loaded before the inflections from the project, we may not see the problem here.

On Rails 3.2 stable this is a problem because the hash is "lazily" looked up and can be interfered by inflections.

[pixeltrix]

@asanghi while your fix does the job I'm thinking that there's a problem with acronym if it converts 'POST' to 'pos_t'. The acronym regex needs to look ahead that the character following the trailing capital letter needs to be a lower case letter, i.e it needs to discern between POST and POSController.

We should still fix the HTTP_METHOD_LOOKUP so that it isn't affected by inflection settings, but can you see if you can tweak the regex to work as I described - thanks.

[asanghi]

@pixeltrix thanks for the input. quite a challenge understanding that regex. Perhaps you can guide me a bit?

Looking at the underscore function's code:

1. word.gsub!(/(?:([A-Za-z\d])|^)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1}#{$1 && '_'}#{$2.downcase}" }
2. word.gsub!(/([A-Z\d]+)([A-Z][a-z])/,'\1_\2')
3. word.gsub!(/([a-z\d])([A-Z])/,'\1_\2')
4. word.tr!("-", "_")
5. word.downcase!

A lot of magic going on here, most of which i can understand except for the first set employing regex which i dont seem to grasp.

POST => posT (1) => pos_T (3) => pos_t (5)

I tried this (sticking a dot in the positive lookahead matcher but it broke another test.

word.gsub!(/(?:([A-Za-z\d])|^)(#{inflections.acronym_regex})(?=\b|[^a-z].)/) { "#{$1}#{$1 && '_'}#{$2.downcase}" }

A bit lost here, @pixeltrix

[pixeltrix]

Sorry @asanghi it turns out that making the existing tests pass and making POST work is an intractable problem. The current tests have IRoRU -> i_ror_u which is indistinguishable by regexp from POST (both have a single trailing capital letter). I'll have to give this some thought as there's quite a few places in the codebase where underscore and camelize are used.

[asanghi]

Yup that's the one that failed. IRoRU .

Can we still go ahead with HTTP_METHOD_LOOKUP merge though? Or club with fix for all other possible problems with underscore and camelize?

[rafaelfranca]

@pixeltrix Is anything missing here?

[pixeltrix]

No - I think we just have to accept that adding POS as an acronym is going to mess up 'POST'.underscore so we just need to be careful about using it where the app's inflections can have an effect.