[performance] IFile.write(byte[]): reduce store.fetchInfo()

Optimistically assume the parent folder already exists on local File
System when it exists in workspace (normal case). So do not explicitly
check it. If it did not exist file write will fail and can be retried
after creating the parent in File System.
This optimization is only implemented for byte[] content in the not
appending case:
 * InputStream content would need a reset.
 * In append mode it is not obvious if something was already appended.

eclipse-platform#1443

resources/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/localstore/FileSystemResourceManager.java

@@ -1211,7 +1211,7 @@ public void write(IFile target, InputStream content, IFileInfo fileInfo, int upd
 		try (content) {
 			Resource targetResource = (Resource) target;
 			IFileStore store = getStore(target);
-			prepareWrite(target, fileInfo, updateFlags, append, targetResource, store);
+			prepareWrite(target, fileInfo, updateFlags, append, targetResource, store, false);
 
 			// On Windows an attempt to open an output stream on a hidden file results in FileNotFoundException.
 			// See https://bugs.eclipse.org/bugs/show_bug.cgi?id=194216
@@ -1243,7 +1243,7 @@ public void write(IFile target, InputStream content, IFileInfo fileInfo, int upd
 	}
 
 	private void prepareWrite(IFile target, IFileInfo fileInfo, int updateFlags, boolean append,
-			Resource targetResource, IFileStore store) throws CoreException {
+			Resource targetResource, IFileStore store, boolean optimistic) throws CoreException {
 		if (fileInfo.getAttribute(EFS.ATTRIBUTE_READ_ONLY)) {
 			String message = NLS.bind(Messages.localstore_couldNotWriteReadOnly, target.getFullPath());
 			throw new ResourceException(IResourceStatus.FAILED_WRITE_LOCAL, target.getFullPath(), message, null);
@@ -1292,11 +1292,14 @@ private void prepareWrite(IFile target, IFileInfo fileInfo, int updateFlags, boo
 			// never move to the history store, because then the file is missing if write
 			// fails
 			getHistoryStore().addState(target.getFullPath(), store, fileInfo, false);
-		if (!fileInfo.exists()) {
-			IFileStore parent = store.getParent();
-			IFileInfo parentInfo = parent.fetchInfo();
-			if (!parentInfo.exists()) {
-				parent.mkdir(EFS.NONE, null);
+		// let's be optimistic that the parent directory exists?
+		if (!optimistic) {
+			if (!fileInfo.exists()) {
+				IFileStore parent = store.getParent();
+				IFileInfo parentInfo = parent.fetchInfo();
+				if (!parentInfo.exists()) {
+					parent.mkdir(EFS.NONE, null);
+				}
 			}
 		}
 	}
@@ -1327,7 +1330,7 @@ public void write(IFile target, byte[] content, IFileInfo fileInfo, int updateFl
 		SubMonitor subMonitor = SubMonitor.convert(monitor, 4);
 		Resource targetResource = (Resource) target;
 		IFileStore store = getStore(target);
-		prepareWrite(target, fileInfo, updateFlags, append, targetResource, store);
+		prepareWrite(target, fileInfo, updateFlags, append, targetResource, store, true);
 
 		// On Windows an attempt to open an output stream on a hidden file results in
 		// FileNotFoundException.
@@ -1342,7 +1345,23 @@ public void write(IFile target, byte[] content, IFileInfo fileInfo, int updateFl
 			subMonitor.split(1);
 		}
 		int options = append ? EFS.APPEND : EFS.NONE;
-		store.write(content, options, subMonitor.split(1));
+		try {
+			store.write(content, options, subMonitor.split(1));
+		} catch (CoreException e) {
+			if (append) {
+				throw e;
+			}
+			if (e.getStatus().getCode() != EFS.ERROR_WRITE) {
+				throw e;
+			}
+			IFileStore parent = store.getParent();
+			IFileInfo parentInfo = parent.fetchInfo();
+			if (!parentInfo.exists()) {
+				parent.mkdir(EFS.NONE, null);
+				// try again
+				store.write(content, options, null);
+			}
+		}
 		if (restoreHiddenAttribute) {
 			fileInfo.setAttribute(EFS.ATTRIBUTE_HIDDEN, true);
 			store.putInfo(fileInfo, EFS.SET_ATTRIBUTES, subMonitor.split(1));

resources/tests/org.eclipse.core.tests.resources/src/org/eclipse/core/tests/resources/IFileTest.java

@@ -45,6 +45,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
+import org.eclipse.core.internal.resources.ResourceException;
 import org.eclipse.core.resources.IContainer;
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IFileState;
@@ -484,6 +485,27 @@ public void testCreateBytes() throws CoreException {
 		assertFalse(derived.isDerived());
 		assertFalse(derived.isTeamPrivateMember());
 		assertEquals("notDerived", derived.readString());
+
+		IFolder subFolder = projects[0].getFolder("subFolder");
+		subFolder.create(true, true, null);
+		subFolder.getRawLocation().toFile().delete();
+
+		IFile orphan = subFolder.getFile("myParentDoesNotExist.txt");
+		monitor.prepare();
+		orphan.write("parentDoesNotExistInFileSystemButInWorkspace".getBytes(), true, false, false, monitor);
+		monitor.assertUsedUp();
+		assertEquals("parentDoesNotExistInFileSystemButInWorkspace", orphan.readString());
+
+		monitor.prepare();
+		orphan.getParent().delete(true, null);
+		// if the parent is deleted in workspace Exception is expected:
+		try {
+			orphan.write("parentDoesNotExist - not even in workspace".getBytes(), true, false, false, monitor);
+			assertFalse("should not be reached", true);
+		} catch (ResourceException expected) {
+			monitor.assertUsedUp();
+			assertFalse(orphan.exists());
+		}
 	}
 
 	@Test