Continuous build: File watcher regression in 2.11 about gradle

[oconnelc]

I haven't isolated at what point it changed, but I have done some preliminary investigation into the cause:

In the file: WatchServiceRegistar.java in the method watch:

void watch(FileSystemSubset fileSystemSubset) throws IOException {
    lock.lock();
    try {
        LOG.debug("Begin - adding watches for {}", fileSystemSubset);
        final WatchPointsRegistry.Delta delta = 
            watchPointsRegistry.appendFileSystemSubset(fileSystemSubset, getCurrentWatchPoints());
            Iterable<? extends File> startingWatchPoints = delta.getStartingWatchPoints();

This method gets called twice. The first time to start the watching of src/main/java, which is added by the JavaPlugin, which is added by WarPlugin.java. In this all the src/main/webapp is rejected in the FileWalker, defined within the watch method:

Files.walkFileTree(dirPath, new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult preVisitDirectory(Path path, BasicFileAttributes attrs) throws IOException {
    if (!path.equals(dirPath)) {
        if (delta.shouldWatch(path.toFile())) {
            watchDir(path);
            return FileVisitResult.CONTINUE;
         } else {
             LOG.debug("Skipping watching for {}, filtered by WatchPointsRegistry", path);
             return FileVisitResult.SKIP_SUBTREE;
         }
     } else {
        return FileVisitResult.CONTINUE;
     }
 });

The call to the delta.shouldWatch is rejected because src/main/webapp is not a child of src/main/java.

In the second pass, a new Delta is created with the following parameters:

fileSystemSubset: with files = $projectDir/topLevel and tree=$projectDIr/src/main/webapp
getCurrentWatchPoints() = {$projectDir/src/main, $projectDir}

when calling the delta.getStartingWatchPoints(), the starting points only contains: $projectDir.

In the for loop that iterates over the starting points, src/main/webapp is skipped because the entire src dir is skipped. This is because the src/main/webapp is defined as a root within the delta. As a result, no watchpoint is ever registered because the delta.shouldWatch() returns false for the src directory and prevents the rest of the subtree from being registered.

I'm not sure what the correct way to resolve this.

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