[ruby-core:79102] [Ruby trunk Feature#13133] TracePoint: Add event type for constant access

Issue #13133 has been reported by Burke Libbey.

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Feature #13133: TracePoint: Add event type for constant access
https://bugs.ruby-lang.org/issues/13133

* Author: Burke Libbey
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Hi there,

I've attached a patch to add a new `:constant_access` TracePoint event.

One feature and/or bug, depending on your perspective: since this event fires from `setinlinecache`, the event is only triggered:

- **after nested constant resolution**: for `A::B`, only one event is triggered (because `getinlinecache/getconstant/getconstant/`**`setinlinecache`**);
- **on cache miss**: it cannot be used for things like counting iterations, which limits possible uses, but reduces overhead (because `getinlinecache` jumps over `setinlinecache` on a hit).

The use-case I have in mind here is to enable building runtime package/component boundary enforcement systems. For this case, both of the above properties are ideal.

Enforcing package boundaries is a problem we've been discussing a lot lately at Shopify.

If you want a more concrete usage example for this patch, I have some [proof-of-concept code](https://github.com/burke/packages) posted that makes use of it to construct a fairly minimal package system. [`Packages::CONSTANT_ACCESS_TRACEPOINT`](https://github.com/burke/packages/blob/master/lib/packages.rb) is the particularly relevant bit.


---Files--------------------------------
0001-add-a-tracepoint-for-constant-access.patch (3.38 KB)


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