build-oudated-file feature is broken

[Egor18]

Hi. I was trying to speed up model building process by building only outdated files, and probably I found some bug.
Here is the code, that I use to build the model:

public static CtModel buildModel(String resourcePath)
{
	Launcher launcher = new Launcher();
	launcher.addInputResource(resourcePath);
	launcher.getEnvironment().setNoClasspath(true);
	launcher.getEnvironment().setCommentEnabled(true);
	launcher.createCompiler();
	launcher.setSourceOutputDirectory("D:/outpath");
	launcher.getModelBuilder().setBuildOnlyOutdatedFiles(true);
	launcher.buildModel();
	launcher.getModelBuilder().generateProcessedSourceFiles(OutputType.COMPILATION_UNITS);
	return launcher.getModel();
}

So, as far as I understand, in order to build only outdated files we need to save spoon-generated source files, and then spoon will compare their modification time with actual source files.
When I run this code at the first time, it works fine (when it builds model from scratch).
But then, if I run this code again, I will get:

Exception in thread "main" java.lang.UnsupportedOperationException
	at java.util.Collections$UnmodifiableCollection.remove(Collections.java:1058)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.keepOutdatedFiles(JDTBasedSpoonCompiler.java:546)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.buildUnits(JDTBasedSpoonCompiler.java:412)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.buildUnitsAndModel(JDTBasedSpoonCompiler.java:377)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.buildSources(JDTBasedSpoonCompiler.java:353)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.build(JDTBasedSpoonCompiler.java:124)
	at spoon.support.compiler.jdt.JDTBasedSpoonCompiler.build(JDTBasedSpoonCompiler.java:107)
	at spoon.Launcher.buildModel(Launcher.java:705)
	at com.pvsstudio.pvsjava.analyzer.Main.buildModel(Main.java:80)
	at com.pvsstudio.pvsjava.analyzer.Main.main(Main.java:138)

I looked through the spoon code, and found this:

protected CompilationUnitDeclaration[] buildUnits(JDTBuilder jdtBuilder, SpoonFolder sourcesFolder, String[] classpath, String debugMessagePrefix, boolean buildOnlyOutdatedFiles) {
	List<SpoonFile> sourceFiles = Collections.unmodifiableList(sourcesFolder.getAllJavaFiles());
	....
	if (buildOnlyOutdatedFiles && outputDirectory.exists()) {
		@SuppressWarnings("unchecked") Collection<File> outputFiles = FileUtils.listFiles(outputDirectory, new String[] { "java" }, true);
		keepOutdatedFiles(sourceFiles, outputFiles);
	}
	....
}

protected void keepOutdatedFiles(List<SpoonFile> files, Collection<File> outputFiles) {
	....
	File f = sf.toFile();
	for (String s : relativeOutputPaths) {
		if (f.getAbsolutePath().endsWith(s)) {
			if (f.lastModified() <= new File(outputDirectory, s).lastModified()) {
				files.remove(sf); // <== But files is unmodifiable list!
			}
		}
	}
}

So, as you can see, exception is thrown because of .remove(sf) call on unmodifiable list.
I'm pretty sure, that sourceFiles should not be an unmodifiableList.
I really want some fix, because without it I can not use incremental model build.

In addition, I've got one more question about model building. Is it possible to use multiple CPU-cores to speed up the build?
Thank you.

[monperrus]

I'm pretty sure, that sourceFiles should not be an unmodifiableList.

you're right. would you propose a pull-request to fix this bug?

[monperrus]

closed per #1913