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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /devtools/client/memory/actions/task-cache.js
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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Add m-esr52 at 52.6.0
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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/. */
+"use strict";
+
+const { assert } = require("devtools/shared/DevToolsUtils");
+
+/**
+ * The `TaskCache` allows for re-using active tasks when spawning a second task
+ * would simply duplicate work and is unnecessary. It maps from a task's unique
+ * key to the promise of its result.
+ */
+const TaskCache = module.exports = class TaskCache {
+ constructor() {
+ this._cache = new Map();
+ }
+
+ /**
+ * Get the promise keyed by the given unique `key`, if one exists.
+ *
+ * @param {Any} key
+ * @returns {Promise<Any> | undefined}
+ */
+ get(key) {
+ return this._cache.get(key);
+ }
+
+ /**
+ * Put the task result promise in the cache and associate it with the given
+ * `key` which must not already have an entry in the cache.
+ *
+ * @param {Any} key
+ * @param {Promise<Any>} promise
+ */
+ put(key, promise) {
+ assert(!this._cache.has(key),
+ "We should not override extant entries");
+
+ this._cache.set(key, promise);
+ }
+
+ /**
+ * Remove the cache entry with the given key.
+ *
+ * @param {Any} key
+ */
+ remove(key) {
+ assert(this._cache.has(key),
+ `Should have an extant entry for key = ${key}`);
+
+ this._cache.delete(key);
+ }
+};
+
+/**
+ * Create a new action-orchestrating task that is automatically cached. The
+ * tasks themselves are responsible from removing themselves from the cache.
+ *
+ * @param {Function(...args) -> Any} getCacheKey
+ * @param {Generator(...args) -> Any} task
+ *
+ * @returns Cacheable, Action-Creating Task
+ */
+TaskCache.declareCacheableTask = function ({ getCacheKey, task }) {
+ const cache = new TaskCache();
+
+ return function (...args) {
+ return function* (dispatch, getState) {
+ const key = getCacheKey(...args);
+
+ const extantResult = cache.get(key);
+ if (extantResult) {
+ return extantResult;
+ }
+
+ // Ensure that we have our new entry in the cache *before* dispatching the
+ // task!
+ let resolve;
+ cache.put(key, new Promise(r => {
+ resolve = r;
+ }));
+
+ resolve(dispatch(function* () {
+ try {
+ args.push(() => cache.remove(key), dispatch, getState);
+ return yield* task(...args);
+ } catch (error) {
+ // Don't perma-cache errors.
+ if (cache.get(key)) {
+ cache.remove(key);
+ }
+ throw error;
+ }
+ }));
+
+ return yield cache.get(key);
+ };
+ };
+};