Wrong usage of Caffeine cache

[infeo]

With PR #164 we switched our caching library from Google's Guave implementation to Caffeine.

Unfortunately, caffeine does not allow recursive updates of the cache (see https://github.com/ben-manes/caffeine/wiki/Faq#recursive-computations), but we are doing it anyway in the CryptoPathMapper class:

	public CiphertextFilePath getCiphertextFilePath(CryptoPath cleartextPath) throws IOException {
		CryptoPath parentPath = cleartextPath.getParent();
		if (parentPath == null) {
			throw new IllegalArgumentException("Invalid file path (must have a parent): " + cleartextPath);
		}
//---------HERE: we call getCiphertextDir(...)
		CiphertextDirectory parent = getCiphertextDir(parentPath);
		String cleartextName = cleartextPath.getFileName().toString();
		return getCiphertextFilePath(parent.path, parent.dirId, cleartextName);
	}


	public CiphertextDirectory getCiphertextDir(CryptoPath cleartextPath) throws IOException {
		assert cleartextPath.isAbsolute();
		CryptoPath parentPath = cleartextPath.getParent();
		if (parentPath == null) {
			return rootDirectory;
		} else {
			try {
//--------------------cache.get() is an if-cached-return-else-create-and-return operation
				return ciphertextDirectories.get(cleartextPath, p -> {
					try {
//-------------------------------HERE: we call getCiphertextFilepath(...)
						Path dirFile = getCiphertextFilePath(p).getDirFilePath();
						return resolveDirectory(dirFile);
					} catch (IOException e) {
						throw new UncheckedIOException(e);
					}
				});
			} catch (UncheckedIOException e) {
				throw new IOException(e);
			}
		}
	}

This leads to the following stacktrace when accessing deeper folderstructures:

java.lang.IllegalStateException: Recursive update

	at java.base/java.util.concurrent.ConcurrentHashMap.compute(ConcurrentHashMap.java:1991)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.BoundedLocalCache.doComputeIfAbsent(BoundedLocalCache.java:2666)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.BoundedLocalCache.computeIfAbsent(BoundedLocalCache.java:2649)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.LocalCache.computeIfAbsent(LocalCache.java:112)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.LocalManualCache.get(LocalManualCache.java:62)
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapper.getCiphertextDir(CryptoPathMapper.java:161)
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapper.getCiphertextFilePath(CryptoPathMapper.java:122)
....//more repetetions of the above stacktrace
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapper.lambda$getCiphertextDir$0(CryptoPathMapper.java:163)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.BoundedLocalCache.lambda$doComputeIfAbsent$14(BoundedLocalCache.java:2668)
	at java.base/java.util.concurrent.ConcurrentHashMap.compute(ConcurrentHashMap.java:1916)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.BoundedLocalCache.doComputeIfAbsent(BoundedLocalCache.java:2666)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.BoundedLocalCache.computeIfAbsent(BoundedLocalCache.java:2649)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.LocalCache.computeIfAbsent(LocalCache.java:112)
	at com.github.benmanes.caffeine/com.github.benmanes.caffeine.cache.LocalManualCache.get(LocalManualCache.java:62)
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapper.getCiphertextDir(CryptoPathMapper.java:161)
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapper.getCiphertextFilePath(CryptoPathMapper.java:122)
	at org.cryptomator.cryptofs/org.cryptomator.cryptofs.CryptoPathMapperTest.testPathEncryptionDEEP(CryptoPathMapperTest.java:173)