Add LinterTrait, which provides the common functions for both SingleRuleLinter and HHClientLinter

[Atry]

No description provided.

[fredemmott]

This feels like it should be an abstract class instead: every linter should use this trait and implement the interface.

[Atry]

This feels like it should be an abstract class instead: every linter should use this trait and implement the interface.

We can turn this trait into an abstract class for now. But it would become a problem if we also create another abstract class for LintRule, because SingleRuleLinter cannot extend both abstract classes.

[fredemmott]

Yeah :( I suspect we'll revisit this once traits are reworked and formalize. We might end up doing base classes and traits - base classes for devx, where the base classes always pull in the traits - but as multiple inheritance isn't supported, SingleRuleLinter would have to use at least one of the traits directly

[Atry]

Yeah :( I suspect we'll revisit this once traits are reworked and formalize. We might end up doing base classes and traits - base classes for devx, where the base classes always pull in the traits - but as multiple inheritance isn't supported, SingleRuleLinter would have to use at least one of the traits directly

By the way, I updated this PR to introduce the BaseLinter as an abstract class, but I feel we could have a better design than this.

I think the best design in Hack, considering the restrictions in the object model, is to minimize the interfaces and to eliminate the demand of sharing implementation between class instances. We can then move helper methods into namespaces as top-level free functions. Each time we want to add a helper, we add it as a free function. Each time we need new methods in the interfaces, we create a new interface containing the new methods instead of changing existing interfaces.

[fredemmott]

Each time we need new methods in the interfaces, we create a new interface containing the new methods instead of changing existing interfaces.

If there's a semantic separation, i agree with this, but not purely as a BC mechanism; large sets of related hierarchies really hurt developer experience. BC vs devx is a tradeoff.

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