feat(pathref): add custom instanceof which will work between versions

src/path.test.ts

@@ -1,5 +1,5 @@
 import { assert, assertEquals, assertRejects, assertThrows, withTempDir } from "./deps.test.ts";
-import { createPathRef } from "./path.ts";
+import { createPathRef, PathRef } from "./path.ts";
 import { path as stdPath } from "./deps.ts";
 
 Deno.test("join", () => {
@@ -489,3 +489,19 @@ Deno.test("pipeTo", async () => {
     assertEquals(otherFilePath.textSync(), largeText);
   });
 });
+
+Deno.test("instanceof check", () => {
+  class OtherPathRef {
+    // should match because of this
+    private static instanceofSymbol = Symbol.for("dax.PathRef");
+
+    static [Symbol.hasInstance](instance: any) {
+      return instance?.constructor?.instanceofSymbol === OtherPathRef.instanceofSymbol;
+    }
+  }
+
+  assert(createPathRef("test") instanceof PathRef);
+  assert(!(new URL("https://example.com") instanceof PathRef));
+  assert(new OtherPathRef() instanceof PathRef);
+  assert(createPathRef("test") instanceof OtherPathRef);
+});

src/path.ts

@@ -14,10 +14,22 @@ export function createPathRef(path: string | URL): PathRef {
 export class PathRef {
   readonly #path: string;
 
+  /** This is a special symbol that allows different versions of
+   * Dax's `PathRef` API to match on `instanceof` checks. Ideally
+   * people shouldn't be mixing versions, but if it happens then
+   * this will maybe reduce some bugs (or cause some... tbd).
+   */
+  private static instanceofSymbol = Symbol.for("dax.PathRef");
+
   constructor(path: string | URL) {
     this.#path = path instanceof URL ? stdPath.fromFileUrl(path) : path;
   }
 
+  static [Symbol.hasInstance](instance: any) {
+    // this should never change because it should work accross versions
+    return instance?.constructor?.instanceofSymbol === PathRef.instanceofSymbol;
+  }
+
   /** Gets the string representation of this path. */
   toString(): string {
     return this.#path;