rake - how does the “directory” keyword work?

Question

It's been stated in several places that "directory" keyword can be used as a shorthand. Apparently, it can be indicated as a dependency, so that it will be created if not already present.

http://onestepback.org/articles/buildingwithrake/directorydependencies.html

The idea is to specify destination directory as a dependency, not to attempt to create it manually each time, which can be achieved by using mkdir_p. Downside of using mkdir_p is that it displays output regardless of whether the directory was already present. An alternative solution is to silence this command -- and even better if the output is displayed only when the directory is created.

I've tried using "directory" keyword as follows:

---

file "destFile" => ["srcFile", directory "myOutputDir"] do
    FileUtils.cp "srcFile" "myOutputDir/destFile"
end

---

file "destFile" => ["srcFile"] + [directory "myOutputDir"] do
    FileUtils.cp "srcFile" "myOutputDir/destFile"
end

---

file "destFile" => ["srcFile"] do
    directory "myOutputDir"
    FileUtils.cp "srcFile" "myOutputDir/destFile"
end

Answer 1

How about this:

directory "myOutputDir"
file "myOutputDir/destFile" => ["srcFile", "myOutputDir"] do
  FileUtils.cp "srcFile" "myOutputDir/destFile"
end

I believe it's supposed to be used as a separate task and specified as a dependency like any other task. It's basically the same as specifying a file task that runs mkdir, but the action is implicit. The syntax is otherwise the same.

directory will also make all layers of subdirectories like so: http://onestepback.org/articles/buildingwithrake/directorydependencies.html