Why does `ScopedValue.where(SCOPE_VALUE, val).call()` throw Exception?

[Andrew Haley]

On 3/23/23 02:52, Josiah Noel wrote:
> Is there a specific reason that call() throws the checked exception, but
> not run()?

Yes.

The signature of Callable.call() is:   V call() throws Exception
The signature of Runnable.run() is:    void run()

Something has to catch the exception.

A previous version of the ScopedValue API had the following method. It was intended for your
situation.

         /**
          * Run a value-returning operation with this set of ScopeLocals bound to values,
          * in the same way as {@code call()}.<p>
          *     If the operation throws an exception, pass it as a single argument to the {@link Function}
          *     {@code handler}. {@code handler} must return a value compatible with the type returned by {@code op}.
          * </p>
          * @param op    the operation to run
          * @param <R>   the type of the result of the function
          * @param handler the handler to be applied if {code op} threw an exception
          * @return the result.
           */
         public final <R> R callOrElse(Callable<R> op,
                                       Function<? super Exception, ? extends R> handler) {
             try {
                 return call(op);
             } catch (Exception e) {
                 return handler.apply(e);
             }
         }

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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