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

Optimistically assume the parent folder already exists on local File
System when it exists in workspace. 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 - which can only happen when the workspace is out
of sync with local 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

@@ -1212,7 +1212,7 @@ 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);
 
 			int options = append ? EFS.APPEND : EFS.NONE;
 			try {
@@ -1254,7 +1254,7 @@ 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 assumeParentDirectoryExists) 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);
@@ -1303,7 +1303,7 @@ 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()) {
+		if (!assumeParentDirectoryExists && !fileInfo.exists()) {
 			IFileStore parent = store.getParent();
 			IFileInfo parentInfo = parent.fetchInfo();
 			if (!parentInfo.exists()) {
@@ -1338,7 +1338,7 @@ 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.
@@ -1353,7 +1353,25 @@ 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()) {
+				throw e;
+			}
+			// create missing folders:
+			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

@@ -46,6 +46,7 @@
 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;
@@ -507,6 +508,27 @@ 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