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Author SHA1 Message Date
Nick Alexander
0a312b4f40 Add an async and async testing framework.
This is a well-worn idea: use a `promise-channel` of `[result nil]` or
`[nil error]` pairs.  The `go-pair` and `<?` macros handle catching
exceptions (important, given that synchronous CLJ code expects to throw
rather than return an error promise or similar), allowing code like:
```
(go-pair
  (let [result (<? (pair-chan-fn))]
    (when (not result)
      (throw (Exception. "No result!")))
    (transform result)))
```
to be expressed naturally.  These are the equivalents of `async` and
`await` in JS.

The implementation is complicated by significant incompatibilities
between CLJ and CLJS.  The solution presented here takes care to
separate the macro definitions into CLJ.  Sadly, this requires
namespacing the per-environment symbols explicitly; but we hope to
minimize such code in files like this.

The most significant restriction to this approach is that consumers must
require the transitive dependencies of the macro-defining modules.  See
the included tests (both CLJ and CLJS) for the appropriate
incantations (for pair-chan, core.async, and test).
2016-07-12 13:56:26 -07:00