find_all on an array of ActiveRecords

In my project, an account has_many entries and an entry
has_and_belongs_to_many tags.
I want to find all of the entries for an account which are tagged with
"some specific tag"

The code which I thought would do this is:
@entries = @account.entries.find_all{|entry|entry.tags.collect{|tag|
tag.name}.include?(@tag.name)}

However, this returns an array containing all entries for the account,
and ignores the include? condition.

While attempting to debug the problem, I simplified the expression:

@entries = @account.entries.find_all{|entry|false}

This too returns an array containing all entries for the account.
@account.entries.class is an Array, so I assume the find_all which I
am calling is Enum#find_all and not ActiveRecord#find_all (whic have
much different functionality!)

Can anybody point out where I am wrong?

I think it indeed IS the ActiveRecord#find_all Method, for the
following reason:

if you call the find_all method directly on the association like:
@account.entries.find_all
without the entries being eager-loaded before, it does an AR#find_all
because @account.entries doesn't hold any objects yet.
This would also explain why the block isn't evaluated: AR#find_all
doesn't take a block.

Rails aliases Enumerable#find with #detect, and #find_all with
#select:

@entries = @account.entries.select{|entry|entry.tags.collect{|tag|
tag.name}.include?(@tag.name)}

this would also work:
@entries = @account.entries.to_a.find_all{|entry|entry.tags.collect{|
tag> tag.name}.include?(@tag.name)}

or, use AR for the whole operation:
@entries = @account.entries.find(:all, :include => :tags, :conditions
=> ["tags.name = ?",@tag.name])
(untested)

Less code, less records fetched by SQL ...

Thank you both, this is very helpful