angular / expressionist.js

Expression parser for Angular 2.0

Angular Expressions

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Copyright 2014 Google, Inc. http://angularjs.org

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

expressionist.js's Issues

Support watching sub-expressions (JSON values) as is done for function parameters

Cross-referencing angular/angular.js#7663

Basically, we do this already for function paramters, it needs to happen for JSON values too.

In fact, if a JSON literal expression contains non-const expressions, then most likely we should exclusively be watching the subexpressions, and not the JSON object itself --- so that we don't end up replacing the whole object and creating garbage.

We already do this for PureFunctionAST (and I don't think this should be removed as cargo cult), so we ought to do it for JSON literal properties too. I can't recall if we're already doing that, but I don't believe we have tests for it. I'll check

Filter evaluation is broken

In trying to fix up some failing tests today, I came across a disabled test which chains multiple filters.

The test fails pretty badly, and it seems that filter evaluation is not really doing what it should be doing. That's OK, but we should fix this. Basically, the filter visitor is being passed change records, but subsequent chained filters are not receiving anything. So, when the filter is evaluated, the incorrect value is passed in, and subsequent chained filters receive no values at all. That's borked :(

The thing I'm not really understanding about the current implementation in JS, is why filter visitor which performs evaluation cares about the watch AST at all. Filters should be called in reaction to a change to their inputs or parameters (basically how a PureFunctionAST would work), and passed the current values of the change records (in my understanding).

The Dart code goes a bit further by evaluating the expressions for each argument, this may also be necessary, but to start with I think just passing the current values for the changed records should be enough.

I'll look into this next week

Duplicate symbol `assert` causes SyntaxError in strict mode

Several files declare a function "assert", which becomes a duplicate symbol after importing rtts-assert.assert as "assert". Since AMD builds are always running in strict mode, this causes problems. Lets rename this function to something less-conflicty

Remove WatchParser

The presence of the WatchParser makes it impossible to use Expressionist without also taking a dependency on Watchtower. That's not good. To fix this, we need to move the WatchParser somewhere else. It could live in Templating or in it's own library.

Feature: support PropertyProxies

In templating, we want to intercept reads/writes to a node. However, adding getters/setters for all properties of node to a proxy object is too slow (we did jsperf tests for this). Solution: introduce PropertyProxies.

A PropertyProxy is an object with the following methods:

• createProxyGet(propertyName): returns a function that gets no arguments and returns the current value
• createProxySet(propertyName): returns a function that gets the new value and applies it.

Integrated into expressionist.js, at every places where a getter/setter is allowed a PropertyProxy should be usable as well.

See angular/watchtower.js#23

Refactor: Hand in parsed AST to WatchParser and not the expression string

To be able to cache the AST of expressions the WatchParser should get the already parsed AST and not the expression string as input.

Feature: provide information whether an expression is assignable

See https://github.com/angular/angular.dart/blob/master/lib/core/parser/syntax.dart
Provide an isAssignable property/function on the Expression.