ES6: In “Proxy, internal 'get' calls”, make the “RegExp.prototype.flags” test future-proof (failing because of hasIndices)

[SebastianSimon]

hasIndices (the d flag) is a new RegExp flag supported in pre-release versions of major browsers. It’s causing the “RegExp.prototype.flags” test in the “Proxy, internal 'get' calls” section to fail again (see #1208).

How can we avoid this in the future? What is this test really testing? It’s not supposed to test RegExp flag support, but implicit get calls to a Proxy (from the flags getter), right? So why not limit the test to one or two well-supported flags? For example:

const queriedProperties = [];

Object.getOwnPropertyDescriptor(RegExp.prototype, "flags")
  .get
  .call(new Proxy({}, {
    get(object, key) {
      queriedProperties.push(key);

      return object[key];
    }
  }));

return queriedProperties.includes("global") && queriedProperties.includes("ignoreCase")
  && queriedProperties.indexOf("global") < queriedProperties.indexOf("ignoreCase"); // Testing order.

Of course, the actual code would probably use var, and other more compatible constructs.

By the way, in the current test, there’s also a typo: // Sorted alphabetically by shortname – "gumsuy".. That should be “gimsuy”, or with the additional flag: “dgimsuy”, but of course this may become obsolete, depending on how the updated test is implemented.

[ljharb]

It's pretty important that the current Proxy test ensure that no unexpected Gets are performed.

RegExp flags are added very rarely; I think it's totally fine to need to update the test when a new one is added.