Avoid a second tree lookup in Workspace.getResourceInfo

resources/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/resources/Workspace.java

@@ -1870,14 +1870,14 @@ public ResourceInfo getResourceInfo(IPath path, boolean phantom, boolean mutable
 				Assert.isNotNull(info, "Tree root info must never be null"); //$NON-NLS-1$
 				return info;
 			}
-			ResourceInfo result = null;
-			if (!tree.includes(path)) {
-				return null;
-			}
+			ResourceInfo result;
 			if (mutable) {
+				if (!tree.includes(path)) {
+					return null;
+				}
 				result = (ResourceInfo) tree.openElementData(path);
 			} else {
-				result = (ResourceInfo) tree.getElementData(path);
+				result = (ResourceInfo) tree.getElementDataOrNull(path);
 			}
 			if (result != null && (!phantom && result.isSet(M_PHANTOM))) {
 				return null;

resources/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java

@@ -384,6 +384,26 @@ public DeltaDataTree getDataTree() {
 		return tree;
 	}
 
+	/**
+	 * Returns the element data for the given element identifier, or
+	 * <code>null</code> if the element is not present in this tree.
+	 * <p>
+	 * Unlike {@link #includes(IPath)} followed by {@link #getElementData(IPath)}
+	 * this performs at most one tree lookup.
+	 */
+	public Object getElementDataOrNull(IPath key) {
+		if (key.isRoot()) {
+			return null;
+		}
+		synchronized (this) {
+			DataTreeLookup lookup = lookupCache; // Grab it in case it's replaced concurrently.
+			if (lookup == null || lookup.key != key) {
+				lookupCache = lookup = tree.lookup(key);
+			}
+			return lookup.isPresent ? lookup.data : null;
+		}
+	}
+
 	/**
 	 * Returns the element data for the given element identifier.
 	 * The given element must be present in this tree.