tools: add makeDisposable function for mobx reactions

tools/mobx.ts

@@ -0,0 +1,23 @@
+/* eslint-disable import/prefer-default-export */
+import type { IReactionDisposer } from 'mobx';
+import { autorun } from 'mobx';
+
+export function makeDisposable(
+  createReaction: () => IReactionDisposer,
+  mustBeDisposed: () => boolean
+) {
+  let disposer: IReactionDisposer | undefined;
+
+  function cleanDisposer() {
+    disposer = undefined;
+  }
+
+  autorun(() => {
+    if (mustBeDisposed()) {
+      if (disposer !== undefined) disposer();
+      cleanDisposer();
+    } else {
+      disposer = createReaction();
+    }
+  });
+}