fixes #81798

src/vs/base/common/map.ts

@@ -117,6 +117,8 @@ export class PathIterator implements IKeyIterator {
 	private _from!: number;
 	private _to!: number;
 
+	constructor(private _splitOnBackslash: boolean = true) { }
+
 	reset(key: string): this {
 		this._value = key.replace(/\\$|\/$/, '');
 		this._from = 0;
@@ -134,7 +136,7 @@ export class PathIterator implements IKeyIterator {
 		let justSeps = true;
 		for (; this._to < this._value.length; this._to++) {
 			const ch = this._value.charCodeAt(this._to);
-			if (ch === CharCode.Slash || ch === CharCode.Backslash) {
+			if (ch === CharCode.Slash || this._splitOnBackslash && ch === CharCode.Backslash) {
 				if (justSeps) {
 					this._from++;
 				} else {

src/vs/base/common/resourceTree.ts

@@ -9,6 +9,7 @@ import { Iterator } from 'vs/base/common/iterator';
 import { relativePath, joinPath } from 'vs/base/common/resources';
 import { URI } from 'vs/base/common/uri';
 import { mapValues } from 'vs/base/common/collections';
+import { PathIterator } from 'vs/base/common/map';
 
 export interface ILeafNode<T, C = void> {
 	readonly uri: URI;
@@ -113,18 +114,18 @@ export class ResourceTree<T extends NonNullable<any>, C> {
 
 	add(uri: URI, element: T): void {
 		const key = relativePath(this.root.uri, uri) || uri.fsPath;
-		const parts = key.split(/[\\\/]/).filter(p => !!p);
+		const iterator = new PathIterator(false).reset(key);
 		let node = this.root;
 		let path = '';
 
-		for (let i = 0; i < parts.length; i++) {
-			const name = parts[i];
+		while (true) {
+			const name = iterator.value();
 			path = path + '/' + name;
 
 			let child = node.get(name);
 
 			if (!child) {
-				if (i < parts.length - 1) {
+				if (iterator.hasNext()) {
 					child = new BranchNode(joinPath(this.root.uri, path), path, this.root.context, node);
 					node.set(name, child);
 				} else {
@@ -135,18 +136,24 @@ export class ResourceTree<T extends NonNullable<any>, C> {
 			}
 
 			if (!(child instanceof BranchNode)) {
-				if (i < parts.length - 1) {
+				if (iterator.hasNext()) {
 					throw new Error('Inconsistent tree: can\'t override leaf with branch.');
 				}
 
 				// replace
 				node.set(name, new LeafNode(uri, path, this.root.context, element));
 				return;
-			} else if (i === parts.length - 1) {
+			} else if (!iterator.hasNext()) {
 				throw new Error('Inconsistent tree: can\'t override branch with leaf.');
 			}
 
 			node = child;
+
+			if (!iterator.hasNext()) {
+				return;
+			}
+
+			iterator.next();
 		}
 	}