Styjun

I must write a plugin to compile files of a certain type not covered by an existing plugin.

My initial requirements are simply that if the input file is changed or if the output is missing, then the task will not be up-to-date. In other words, I want the core "working with files" paradigm to work for me.

My first attempt was to declare both inputs and outputs to see if the project would work as most would expect.

class TestPlugin implements Plugin<Project> 
 void apply (Project project) 
 project.task('compile') 
 doFirst 
 inputs.files.eachWithIndex inFilename, idx ->
 def inFile = project.file(inFilename)
 def outFilename = outputs.files[idx]
 def outFile = project.file(outFilename)
 logger.info "converting $inFile to $outFile"
 outFile.append "something"
 
 
 
 

apply plugin: TestPlugin
compile 
 inputs.file "test.in"
 outputs.file "test.out"

And it does. At this point it does all I need except for one thing: I have to define outputs in correlation with inputs. But defining the outputs is complicated enough to warrant factoring that part of the code into the plugin's task.

My next attempt was to try to get the task to define its outputs but it fails because when the "populate outputs" code executes, inputs is empty and so no outputs are added.

class TestPlugin implements Plugin<Project> 
 void apply (Project project) 
 project.task('compile') 
 inputs.files.each outputs.files.add(it.replaceFirst(~/.in$/, '.out')) 
 doFirst 
 inputs.files.eachWithIndex inFilename, idx ->
 def inFile = project.file(inFilename)
 def outFilename = outputs.files[idx]
 def outFile = project.file(outFilename)
 logger.info "converting $inFile to $outFile"
 outFile.append "something"
 
 
 
 

apply plugin: TestPlugin
compile inputs.file "test.in" 

The above fails with a "path may not be null..." error caused by indexing an empty outputs list (because inputs is empty at the time the task's outer block iterates over inputs.

I tried populating outputs in Project.afterEvaluate and Project.beforeEvaluate but neither worked. The beforeEvaluate closure never executed. The afterEvaluate closure executed, well, after the project was evaluated which means it executed after the task was set as either up-to-date or out-of-date and so it's not useful for what I need.

I also tried Project.configure but that didn't work either.

Then I discovered lazy configuration but since it's incubating I think I should avoid it. I'm assuming that the Java and C plugins don't use incubating features and that leaves me wondering how those plugins are accomplishing the equivalent of lazy configuration.

Then I found Gradle plugin for custom language but it doesn't have an answer. It does, however, have a comment leading me to look at a lot of gradle source code. Again, I don't think I should have to reinvent the wheel.

Lastly, if I have to push the decision to compile into doFirst and not bother with declaring outputs (and thereby abandon task up-to-datedness), then so be it. I just need to know and move on.

For more context, I'm migrating a build away from ant. The two udemy.com classes I took helped me a lot but didn't go far enough to lead me in a confident direction to solve the stated problem. I asked a similar question to one of the instructors and its community to no avail.