Solution without generators #4

DavidBruant · 2019-12-07T16:09:32Z

I tried it mostly for fun
Sharing the result in case it's useful
All tests pass, but i'm not sure there are enough tests to consider this solution valid

Fixes #3

Chris-Hibbert · 2019-12-09T22:15:48Z

Thanks, David! I like the style of invocation here much better than the generator style. I'll leave it to MarkM to opine on whether this is secure in the way he's looking for and other language-level issues.

erights

LGTM++!!

After the first skim I was concerned whether you preserved the security properties of the original. You did exactly. Your's is superior in every way.

The reason I avoided this style, and set about looking for another way, was because I knew that the hypothetical future Jessie static verifier would have a problem with the shared mutable object. However, to "solve" this problem, I turned to generators, which is definitely not in Jessie. If we're going to make special cases in the Jessie verifier to allow layer-cakes, I'd rather find special cases to support your pattern than mine.

Good!

erights · 2019-12-10T00:29:28Z

Could you also update the README to match? Thanks.

DavidBruant · 2019-12-10T08:49:13Z

After the first skim I was concerned whether you preserved the security properties of the original

Is there a way to capture all or some of these in the form of one or a couple of unit tests?

Could you also update the README to match?

ok, i'll do that

DavidBruant · 2019-12-27T17:07:39Z

I'm not fully sure about the wording of "intermediate function"

erights

Looks very close to me ;)

erights · 2019-12-27T18:35:19Z

README.md


 ## The Objects-as-closures Pattern

-The classic object or object-oriented programming has public methods and private instance variables. There are several ways to encode this in JavaScript. The following code uses JavaScript's class syntax with the new support for private instance variables.
+The classic object or object-oriented programming has public methods and private instance variables. There are several ways to encode this in JavaScript. The following code uses JavaScript's class syntax with the [new support for private instance variables](https://github.com/tc39/proposal-private-methods).


That link is specifically private methods, rather than private state variables. Use https://github.com/tc39/proposal-class-fields#private-fields instead.

erights · 2019-12-27T18:39:31Z

README.md

@@ -91,9 +91,9 @@ function makeWobblyPoint(x, y, wobble) {

 The pattern above has more of the flexibility associated with traits or mixins. Each layer is expressed separately. The layers are then combined by a distinct maker function `makeWobblyPoint`. Different making functions can combine overlapping sets of layers in different manners.

-The code for expressing the combinable layers is written in the peculiar manner shown above, using generators. We introduce this peculiar generator pattern to solve a hard problem: The code in each layer needs to capture a lexical variable that refers to the object as a whole. However, the object-as-a-whole is not yet assembled, and will be assembled only by a distinct piece of code written in a distinct scope.
+The code for expressing the combinable layers is written in the peculiar manner shown above, using intermediate function. We introduce this peculiar pattern to solve a hard problem: The code in each layer needs to capture a lexical variable that refers to the object as a whole. However, the object-as-a-whole is not yet assembled, and will be assembled only by a distinct piece of code written in a distinct scope.


using an intermediate

The object-as-a-whole explanation is no longer compelling because we're not assembling the object before binding it. There is no such hard problem.

erights · 2019-12-27T18:41:02Z

README.md


-In the generator function pattern shown above, the methods of a given layer are defined in the scope of variables such as `self` and `supr` that are bound on the left of the `yield`. These are bound to values extracted from the value that the `yield` returns. However, before that happens, the generator yields the argument to `yield`, the object containing that layer's methods, to be combined to make the object itself. The helper function `makeClassCake` exported by this repository first runs through the list of generators it is given, extracting the layer functions from each, combining them into the overall object. Only when the object is complete does it go back to these generators, in order to bind that object to each layer's `self` variable.
+In the pattern shown above, the methods of a given layer are defined in the scope of variables such as `self` and `supr` that are provided as arguments to the intermediate function. The helper function `makeClassCake` exported by this repository first runs through all the intermediate functions it is given, extracting the layer functions from each, combining them into the overall object. Only when the object is complete does it go back to these generators, in order to bind that object to each layer's `self` variable.


For the same reason, this paragraph doesn't really make sense. makeClassCake doesn't first extract anything. Also, no generators.

erights · 2019-12-27T19:28:31Z

lib/layer-cake.js

+      suprs.push(nextSupr)
+    }
+
+    return finalObject;


Harden. See #5

erights · 2019-12-27T19:29:07Z

test/test-class-cake.js

-    function* BasePointLayer(x, y) {
-      const [self] = yield {
+    function BasePointLayer(x, y) {
+      return self => ({


Harden the returned record. See #5

erights · 2019-12-27T19:29:21Z

test/test-class-cake.js

-    function* WobblyPointLayer(wobble) {
-      const [_self, supr] = yield {
+    function WobblyPointLayer(wobble) {
+      return (_self, supr) => ({


Likewise. And below.

erights · 2019-12-27T19:32:11Z

test/test-trait-cake.js

-        }),
-      );
+    function AbstractPointLayer(x, y) {
+      return self => harden({


Now that we're only testing the hardening cases, you can just remove redundant cases.

DavidBruant · 2020-01-08T15:18:39Z

@erights ping (in case you haven't seen it)

erights

LGTM, thanks!

DavidBruant · 2020-01-09T14:01:57Z

i'm realizing now i do not have the rights to merge a PR on this repo...

Solution without generators

8a3d9a6

erights approved these changes Dec 10, 2019

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Adjust readme to describe the new generator-less pattern

9317f17

DavidBruant requested a review from erights December 27, 2019 17:07

DavidBruant mentioned this pull request Dec 27, 2019

[ERTP] Move away from generator-based composition of mint configuration Agoric/agoric-sdk#375

Closed

erights requested changes Dec 27, 2019

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Address @erights comments

7793e14

DavidBruant requested a review from erights December 31, 2019 10:23

erights approved these changes Jan 9, 2020

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Fix main/module/browser in package.json

a8e743a

michaelfig merged commit 777313d into Agoric:master Jan 9, 2020

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Solution without generators #4

Solution without generators #4

DavidBruant commented Dec 7, 2019

Chris-Hibbert commented Dec 9, 2019

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DavidBruant commented Jan 9, 2020


		In the generator function pattern shown above, the methods of a given layer are defined in the scope of variables such as `self` and `supr` that are bound on the left of the `yield`. These are bound to values extracted from the value that the `yield` returns. However, before that happens, the generator yields the argument to `yield`, the object containing that layer's methods, to be combined to make the object itself. The helper function `makeClassCake` exported by this repository first runs through the list of generators it is given, extracting the layer functions from each, combining them into the overall object. Only when the object is complete does it go back to these generators, in order to bind that object to each layer's `self` variable.
		In the pattern shown above, the methods of a given layer are defined in the scope of variables such as `self` and `supr` that are provided as arguments to the intermediate function. The helper function `makeClassCake` exported by this repository first runs through all the intermediate functions it is given, extracting the layer functions from each, combining them into the overall object. Only when the object is complete does it go back to these generators, in order to bind that object to each layer's `self` variable.

Solution without generators #4

Solution without generators #4

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