Compile error when upgrading to 4.1.0

[remko]

I'm getting a compile error when upgrading from 4.0.0 to 4.1.0rc:

Message:

NoMethodError: undefined method `reps' for nil:NilClass

Compilation stack:

  (empty)

Stack trace:

  0. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/base/views/item_view.rb:79:in `reps'
  1. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/base/views/item_view.rb:35:in `path'
  2. /Users/remko/src/site/Rules:120:in `block in parse'
  3. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/rule_dsl/rule.rb:58:in `instance_exec'
  4. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/rule_dsl/rule.rb:58:in `apply_to'
  5. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/rule_dsl/rule_memory_calculator.rb:67:in `new_rule_memory_for_rep'
  6. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/rule_dsl/rule_memory_calculator.rb:34:in `[]'
  7. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/base/memoization.rb:54:in `block in memoize'
  8. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/rule_dsl/action_provider.rb:35:in `memory_for'
  9. /Users/remko/.rvm/gems/ruby-2.2.1/gems/nanoc-4.1.0rc1/lib/nanoc/base/services/item_rep_r

The rule looks like this:

   compile '/blog/**/*.md', rep: :linked_excerpt do
    filter :rdiscount, extensions: [:smart]
    filter :more_filter, more_url: item.path
   end

It seems to be the item.path triggering the problem. Is this something that isn't allowed anymore?

[denisdefreyne]

item.path is indeed the cause of the issue.

In the context of a #compile (or #route or #preprocess) block, it is tricky to get hold of the path of the item currently being compiled, because in Nanoc 4.1, the path could be assigned afterwards, e.g. when using the new #write method:

compile '/blog/**/*.md', rep: :linked_excerpt do
  filter :rdiscount, extensions: [:smart]
  filter :more_filter, more_url: item.path
  write item.identifier.without_ext + '/index.html'
end

In this example, you’d be using the path before it’s even known.

This is not a new problem—the fact that the #path method is accessible on an item in Nanoc 4.0 is a bug. Using it this way will likely trip up the dependency tracker, causing items to be unnecessarily recompiled, or not recompiled when they should be.

I’m working on a fix which will make #path (and related methods, such as #compiled_content, which makes even less sense in a compilation rule) inaccessible, i.e. raise a NoMethodError.

In the mean time, the recommended approach would be to pass the item in its entirely to the :more_filter filter:

compile '/blog/**/*.md', rep: :linked_excerpt do
  filter :rdiscount, extensions: [:smart]
  filter :more_filter, more_item: item
end

:more_filter can then itself get the path of the item using params.fetch(:more_item).path.

[denisdefreyne]

Underlying issue is fixed in #768. (item.path will now raise an error.)