fix(unstable): otel context with multiple keys (#27230)

`SafeMap` treats its argument as an object with a "length" and index
properties, rather than a generic iterator, so every time we cloned it,
it was dropping all the data.

ext/telemetry/telemetry.ts

@@ -39,7 +39,6 @@ const {
   SafeWeakMap,
   Array,
   ObjectEntries,
-  SafeMap,
   ReflectApply,
   SymbolFor,
   Error,
@@ -617,26 +616,25 @@ class SpanExporter {
 const CURRENT = new AsyncVariable();
 
 class Context {
-  #data = new SafeMap();
+  #data: Record<symbol, unknown> = { __proto__: null };
 
-  // deno-lint-ignore no-explicit-any
-  constructor(data?: Iterable<readonly [any, any]> | null | undefined) {
-    this.#data = data ? new SafeMap(data) : new SafeMap();
+  constructor(data?: Record<symbol, unknown> | null | undefined) {
+    this.#data = { __proto__: null, ...data };
   }
 
   getValue(key: symbol): unknown {
-    return this.#data.get(key);
+    return this.#data[key];
   }
 
   setValue(key: symbol, value: unknown): Context {
     const c = new Context(this.#data);
-    c.#data.set(key, value);
+    c.#data[key] = value;
     return c;
   }
 
   deleteValue(key: symbol): Context {
     const c = new Context(this.#data);
-    c.#data.delete(key);
+    delete c.#data[key];
     return c;
   }
 }

tests/specs/cli/otel_basic/__test__.jsonc

@@ -19,6 +19,10 @@
     {
       "args": "run -A main.ts metric.ts",
       "output": "metric.out"
+    },
+    {
+      "args": "run -A --unstable-otel context.ts",
+      "output": ""
     }
   ]
 }

tests/specs/cli/otel_basic/context.ts

@@ -0,0 +1,26 @@
+import { assertEquals } from "@std/assert";
+
+const { ContextManager } = Deno.telemetry;
+
+const cm = new ContextManager();
+
+const a = cm.active();
+const b = a.setValue("b", 1);
+const c = b.setValue("c", 2);
+
+const subB = c.deleteValue("b");
+const subC = subB.deleteValue("c");
+
+assertEquals(a.getValue("b"), undefined);
+assertEquals(b.getValue("b"), 1);
+assertEquals(c.getValue("b"), 1);
+
+assertEquals(a.getValue("c"), undefined);
+assertEquals(b.getValue("c"), undefined);
+assertEquals(c.getValue("c"), 2);
+
+assertEquals(subB.getValue("b"), undefined);
+assertEquals(subB.getValue("c"), 2);
+
+assertEquals(subC.getValue("b"), undefined);
+assertEquals(subC.getValue("c"), undefined);