Check if span is active when set as root

Use the `setRoot` function to set the root span. Make sure that when the
root span is set, it's still open. If it's not open, don't set it.
Setting a closed root span is a worse experience and may break things,
because it introduces a broken state.

packages/nodejs/.changesets/only-allow-open-root-spans-to-be-set-as-root.md

@@ -0,0 +1,6 @@
+---
+bump: "patch"
+type: "fix"
+---
+
+Only allow open root spans to be set as root. This avoids closed root spans to be reused in child contexts.

packages/nodejs/src/__tests__/scope.test.ts

@@ -108,6 +108,18 @@ describe("ScopeManager", () => {
       expect(scopeManager.root()).toBe(span)
       expect(scopeManager.active()).toBe(span)
     })
+
+    it("when root span is closed, it doesn't overwrite the root span", () => {
+      const span1 = new RootSpan()
+      scopeManager.setRoot(span1)
+
+      const span2 = new RootSpan()
+      span2.close()
+      scopeManager.setRoot(span2)
+
+      expect(scopeManager.root()).toBe(span1)
+      expect(scopeManager.active()).toBe(span1)
+    })
   })
 
   describe(".root()", () => {

packages/nodejs/src/scope.ts

@@ -140,9 +140,11 @@ export class ScopeManager {
    * Sets the root `Span`
    */
   public setRoot(rootSpan: Span) {
-    const uid = asyncHooks.executionAsyncId()
-    this.#roots.set(uid, rootSpan)
-    this.#scopes.set(uid, rootSpan)
+    if (rootSpan.open) {
+      const uid = asyncHooks.executionAsyncId()
+      this.#roots.set(uid, rootSpan)
+      this.#scopes.set(uid, rootSpan)
+    }
   }
 
   /*