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diff --git a/devtools/client/debugger/src/utils/memoizableAction.js b/devtools/client/debugger/src/utils/memoizableAction.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+import { asSettled } from "./async-value";
+import { validateContext } from "./context";
+
+/*
+ * memoizableActon is a utility for actions that should only be performed
+ * once per key. It is useful for loading sources, parsing symbols ...
+ *
+ * @getValue - gets the result from the redux store
+ * @createKey - creates a key for the requests map
+ * @action - kicks off the async work for the action
+ *
+ *
+ * For Example
+ *
+ * export const setItem = memoizeableAction(
+ *   "setItem",
+ *   {
+ *     hasValue: ({ a }, { getState }) => hasItem(getState(), a),
+ *     getValue: ({ a }, { getState }) => getItem(getState(), a),
+ *     createKey: ({ a }) => a,
+ *     action: ({ a }, thunkArgs) => doSetItem(a, thunkArgs)
+ *   }
+ * );
+ *
+ */
+export function memoizeableAction(name, { getValue, createKey, action }) {
+  const requests = new Map();
+  return args => async thunkArgs => {
+    let result = asSettled(getValue(args, thunkArgs));
+    if (!result) {
+      const key = createKey(args, thunkArgs);
+      if (!requests.has(key)) {
+        requests.set(
+          key,
+          (async () => {
+            try {
+              await action(args, thunkArgs);
+            } catch (e) {
+              console.warn(`Action ${name} had an exception:`, e);
+            } finally {
+              requests.delete(key);
+            }
+          })()
+        );
+      }
+
+      await requests.get(key);
+
+      if (args.cx) {
+        validateContext(thunkArgs.getState(), args.cx);
+      }
+
+      result = asSettled(getValue(args, thunkArgs));
+      if (!result) {
+        // Returning null here is not ideal. This means that the action
+        // resolved but 'getValue' didn't return a loaded value, for instance
+        // if the data the action was meant to store was deleted. In a perfect
+        // world we'd throw a ContextError here or handle cancellation somehow.
+        // Throwing will also allow us to change the return type on the action
+        // to always return a promise for the getValue AsyncValue type, but
+        // for now we have to add an additional '| null' for this case.
+        return null;
+      }
+    }
+
+    if (result.state === "rejected") {
+      throw result.value;
+    }
+    return result.value;
+  };
+}