[ruby-core:98774] [Ruby master Bug#16959] Weakmap has specs and third-party usage despite being a private API

Issue #16959 has been updated by chrisseaton (Chris Seaton).


> I suspect the addition of the specs led to folks starting to use this private API.

I think it's the other way around - the specs were added because people were using it - https://github.com/oracle/truffleruby/issues/1385 and https://github.com/oracle/truffleruby/issues/1958 is what led to the specs being written.

The example you give which all lead back to the Rails PR was written well *before* the specs - April 2019, and the specs were just written I believe, but maybe there is more context to why it was merged that is not referenced?

So I don't think it's right to blame the specs here. The specs reflect reality.

But I do think it could be worth having a conversation about moving some specs to an optional namespace - the C extension API is in there. It'd mark intent at least.

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Bug #16959: Weakmap has specs and third-party usage despite being a private API
https://bugs.ruby-lang.org/issues/16959#change-86131

* Author: headius (Charles Nutter)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
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Weakmap is still described as an internal API, and the documentation points users at WeakRef as the official public API:

https://github.com/ruby/ruby/blob/1fb16dbb6e28b9f32f92554d29e646e088b21a98/gc.c#L11928-L11936

However there are now specs for its current set of features, even though those features have never been discussed or approved as a public API:

https://github.com/ruby/spec/tree/dd8437628a6f2de5b74b338d4960682bb1590a60/core/objectspace/weakmap

And we are starting to see it being used by the community:

* https://github.com/jruby/jruby/issues/6267
* https://github.com/rsim/oracle-enhanced/issues/2027 
* https://github.com/rails/rails/pull/39121

One of two things needs to happen:

* Weakmap is made a public API after some discussion. It would be an official public feature only in 2.8/3.0 or higher.
* The specs are be removed and Weakmap remains a private API not to be used by the community. I suspect the addition of the specs led to folks starting to use this private API.

Personally, I'm in much more in favor of making WeakRef support all the features necessary to implement Weakmap in pure Ruby, rather than the other way around:

https://bugs.ruby-lang.org/issues/6309

But whatever happens it needs to happen soon, since this use case is now a merged feature in Rails master.



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