access-expr: cache evaluations (#27359)

* amp-access: cache evaluations

* create cachekey off based on data

* fix tests

* update cache invalidation strategy

* lint

* move tests to all flow through the class

* eval() is a blacklisted name

* relint

* you missed a spot

* callCount.equal(1) --> calledOnce

* private ivar

extensions/amp-access/0.1/access-expr.js

@@ -14,10 +14,11 @@
  * limitations under the License.
  */
 
+import {hasOwn, map} from '../../../src/utils/object';
 import {accessParser as parser} from '../../../build/parsers/access-expr-impl';
 
 /**
- * Evaluates access expression.
+ * Evaluates access expressions.
  *
  * The grammar is defined in the `access-expr-impl.jison` and compiled using
  * (Jison)[https://zaach.github.io/jison/] parser. The compilation steps are
@@ -44,3 +45,51 @@ export function evaluateAccessExpr(expr, data) {
     parser.yy = null;
   }
 }
+
+/**
+ * AmpAccessEvaluator evaluates amp-access expressions.
+ * It uses a cache to speed up repeated evals for the same expression.
+ */
+export class AmpAccessEvaluator {
+  /** */
+  constructor() {
+    /** @type {Object<string, boolean>} */
+    this.cache = null;
+
+    /** @private @type {JsonObject} */
+    this.lastData_ = null;
+  }
+
+  /**
+   * Evaluate access expressions, but turn to a cache first.
+   * Cache is invalidated when given new data.
+   *
+   * @param {string} expr
+   * @param {!JsonObject} data
+   * @return {boolean}
+   */
+  evaluate(expr, data) {
+    if (this.lastData_ !== data) {
+      this.lastData_ = data;
+      this.cache = map();
+    }
+
+    if (!hasOwn(this.cache, expr)) {
+      this.cache[expr] = this.eval_(expr, data);
+    }
+
+    return this.cache[expr];
+  }
+
+  /**
+   * Evaluates access expressions by proxying calls to evaluateAccessExpr.
+   * This function only exists to be spied on.
+   *
+   * @param {string} expr
+   * @param {!JsonObject} data
+   * @return {boolean}
+   */
+  eval_(expr, data) {
+    return evaluateAccessExpr(expr, data);
+  }
+}

extensions/amp-access/0.1/amp-access.js

@@ -17,14 +17,14 @@
 import {AccessSource, AccessType} from './amp-access-source';
 import {AccessVars} from './access-vars';
 import {ActionTrust} from '../../../src/action-constants';
+import {AmpAccessEvaluator} from './access-expr';
 import {AmpEvents} from '../../../src/amp-events';
 import {CSS} from '../../../build/amp-access-0.1.css';
 import {Observable} from '../../../src/observable';
 import {Services} from '../../../src/services';
 import {cancellation} from '../../../src/error';
 import {dev, user, userAssert} from '../../../src/log';
 import {dict} from '../../../src/utils/object';
-import {evaluateAccessExpr} from './access-expr';
 import {getSourceOrigin} from '../../../src/url';
 import {getValueForExpr, tryParseJson} from '../../../src/json';
 import {installStylesForDoc} from '../../../src/style-installer';
@@ -101,6 +101,9 @@ export class AccessService {
     /** @private {?Promise<string>} */
     this.readerIdPromise_ = null;
 
+    /** @private {!./access-expr.AmpAccessEvaluator} */
+    this.evaluator_ = new AmpAccessEvaluator();
+
     /** @const */
     this.sources_ = this.parseConfig_();
 
@@ -452,7 +455,7 @@ export class AccessService {
    */
   applyAuthorizationToElement_(element, response) {
     const expr = element.getAttribute('amp-access');
-    const on = evaluateAccessExpr(expr, response);
+    const on = this.evaluator_.evaluate(expr, response);
     let renderPromise = null;
     if (on) {
       renderPromise = this.renderTemplates_(element, response);