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Rationale

It can be difficult to manage resource lifetimes, especially when laziness is involved. Simply local scoping can be inadequate. Resource scopes can decouple resource lifetimes from creating scope.

Plan

  • Generalize from resource scopes to general scopes (succeed/fail/exit)
  • with-open et al make scopes
  • Some design work and code has been done

Use Cases

  • REPL usage: open stream and it closes before I lazily consume it. Doh!
  • Start an activity, and then have nested resource lifetime automatically tie to it
    • Task A calls Iib B which allocates resources
  • Prevent resource lifetimes from nesting
    • lib C knows it doesn't want its lifetime governed by Task A
  • All works across threads

Issues

  • Consider threads as well as nesting
  • How do scopes interact with io! and stm
  • Can we hydrate the fork/join tree where we need it?
  • How to prevent mess?
    • (when-scope :fails ...) et al are very declarative
    • but are setting up non-local effects
    • potentially leading to wtf when triggered
    • is this the right external API?
      • any way to ensure correctness
      • will we be beset with requests for order control
  • Is the nearest enclosing scope always the right one?
    • what to do if not
      • named scopes
      • scopes as args
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