Gradle file rename causes circular dependency error - Why? - gradle

Question

I want to store an input file in a JAR created with a subclass of the Jar task in Gradle. The input file shall be stored under a different name.
Here is my build.gradle (complete working example; just create dir1/file1.txt first):
task myjar(type: MyJarTask);
class MyJarTask extends Jar {
#InputFile
File file1 = new File('dir1/file1.txt');
public MyJarTask() {
configure {
baseName 'foo'
from {
file1;
// comment out the next line to eliminate the error:
rename { String fileName -> fileName.replace('file1.txt', 'file2.txt'); }
}
}
}
}
Running this via gradle myjar gives the following error:
* What went wrong:
Circular dependency between the following tasks:
:myjar
\--- :myjar (*)
(*) - details omitted (listed previously)
When I comment out the line with the rename, everything works! (Of course the file is not renamed.)
What is the reason for this surprising behavior? Are we witnessing a Gradle bug?
Please do not suggest alternative solutions; I solved the original problem by avoiding the need for the rename. But I would like to learn; I feel I am missing something important.

Answer 1

I got an answer on the Gradle forum by Sterling Greene of Gradleware. Basically, the cause of the circular dependency is this (in my own words):
Closures always return the last value, so the from {} closure returns the value of rename. Incidentally, rename returns a reference to the task itself (why it would do that, I don't know, but that's what its docs say). So the task itself is added to its list of things to copy, and we have a circular dependency.
The solution would be to modify the closure slightly:
from(file1) {
//file1;
rename { String fileName -> fileName.replace('file1.txt', 'file2.txt'); }
}
This runs with no problems, because it uses an overloaded variant of the from() method which always adds the given file to the list of things to copy, not the result of the closure. All in all, that's not exactly intuitive, but there it is.

Answer 2

Well i also got same error I thought error was due to renaming of files but in my case error was due to dual dependency on module(:backend)and java library dependency on android module(:app) I got it sorted by following steps:
Press Ctrl+Shift+Alt+S or Go to File->Project Structure this will open project Structure Dialog box.
On left side PANEL ,under modules section choose java library (e.g jjLibrary) there was two compile dependency :app and :backend just have to remove both of these dependencies.As :backend already have compile dependency on java library and :app is android module which cannot have dependency on java library.Press Ok.
Save and Sync gradle files ..
And the error has gone..Hope this helps!!!Cheers