breadcrumbs_trail misbehaves if item identifiers have more than one "."

[iay]

Items with more than one "." in their identifier (e.g., "1.6.md") can cause breadcrumbs_trail to reference the wrong item.

Steps to reproduce

Make items like this:

/trp/1.5.md
/trp/1.5/foo.md
/trp/1.6.md
/trp/1.6/foo.md

The breadcrumbs for one or other of the foo.md items will refer to the wrong parent.

Expected behavior

I'd expect the last element of the breadcrumb trail for an item to always be that item's parent.

Actual behavior

Sometimes the last element of the breadcrumb trail for an item can be an item with a similar name.

Details

It looks like the breadcrumbs_trail method for full identifiers is stripping extensions for identifier components other than the last: here

@items[Nanoc::Identifier.new(pr).without_ext + '.*']

For example, for /trp/1.6/software.md:

• components becomes ["", "/trp", "/trp/1.6", "/trp/1.6/software.md"]

• The identifiers used to construct the prefixes array are: ["/index.*", "/trp.*", "/trp/1.*", "/trp/1.6/software.*"]

Note that "/trp/1.*" can match either /trp/1.5.md or /trp/1.6.md.

It seems to me as if stripping the extension isn't required here, as long as you don't add the .* on to the end of the last identifier in the list: that one will already be present as an explicit extension if we're working with full identifiers.

I could be missing something, though, I am really not a native Ruby programmer (yet).

[iay]

Changing this:

        prefixes
          .reject { |pr| pr =~ /^\/index\./ }
          .map do |pr|
            if pr == ''
              @items['/index.*']
            else
              @items[Nanoc::Identifier.new(pr).without_ext + '.*']
            end
          end

to this:

        prefixes.push(Nanoc::Identifier.new(prefixes.pop).without_ext)
        prefixes
          .reject { |pr| pr =~ /^\/index\./ }
          .map do |pr|
            if pr == ''
              @items['/index.*']
            else
              @items[Nanoc::Identifier.new(pr) + '.*']
            end
          end
      end

... appears to fix the problem in my case, by only stripping the extension from the last prefix (representing the current item itself). I doubt that it's idiomatic Ruby, and I can't find any unit tests to run to see if it would break something else. But it's a start. I can set up a PR if you want one.

[iay]

Alas, that quick fix does indeed run into an additional problem with the /index.md item, as it is no longer matched in the .reject clause, so you end up with two references to itself from the root item.

This variant appears to address that:

        prefixes.push(Nanoc::Identifier.new(prefixes.pop).without_ext)
        prefixes
          .reject { |pr| pr =~ /^\/index$/ }
          .map do |pr|
            if pr == ''
              @items['/index.*']
            else
              @items[Nanoc::Identifier.new(pr) + '.*']
            end
          end

[denisdefreyne]

I believe that the purpose of #without_ext was to support items with multiple extensions, like these:

/foo/stuff.md
/foo.md.erb

[denisdefreyne]

There is a fix in #1279 with some fancy functional programming ✨