have stop_mirai() return either TRUE or FALSE

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: mirai
 Type: Package
 Title: Minimalist Async Evaluation Framework for R
-Version: 1.3.1.9017
+Version: 1.3.1.9018
 Description: Designed for simplicity, a 'mirai' evaluates an R expression
     asynchronously in a parallel process, locally or distributed over the
     network, with the result automatically available upon completion. Modern

NEWS.md

@@ -1,4 +1,4 @@
-# mirai 1.3.1.9017 (development)
+# mirai 1.3.1.9018 (development)
 
 #### Architecture Change
 

R/dispatcher.R

@@ -160,16 +160,13 @@ dispatcher <- function(host, url = NULL, n = NULL, ..., tls = NULL, pass = NULL,
                 found <- TRUE
                 break
               }
-            if (found) {
-              found <- NA
-            } else {
+            if (!found)
               for (i in seq_along(inq))
                 if (inq[[i]][["msgid"]] == id) {
                   inq[[i]] <- NULL
                   found <- TRUE
                   break
                 }
-            }
             send(ctx, found, mode = 2L, block = TRUE)
           } else {
             status <- c(

R/mirai.R

@@ -391,19 +391,22 @@ collect_mirai <- collect_aio
 #' Stops a \sQuote{mirai} if still in progress, causing it to resolve
 #' immediately to an \sQuote{errorValue} 20 (Operation canceled).
 #'
-#' In the case that the \sQuote{mirai} is in execution and an interrupt was
-#' sent, the task or a portion of it may have completed before the interrupt is
-#' received, and even then it is not always possible to immediately interrupt
-#' evaluation (especially if it is compiled code).
+#' Using dispatcher allows cancellation of \sQuote{mirai}. In the case that the
+#' \sQuote{mirai} is awaiting execution, it is discarded from the queue and
+#' never evaluated. In the case it is already in execution, an interrupt will be
+#' sent. A successful cancellation request does not guarantee successful
+#' cancellation. Note that the task, or a portion of it, may have already
+#' completed before the interrupt is received. Even then it is not always
+#' possible to immediately interrupt, for example, compiled code. This should be
+#' noted particularly if the code carries out side effects during execution,
+#' such as writing to files, etc.
 #'
 #' @inheritParams call_mirai
 #'
-#' @return A logical value: \code{TRUE} if the cancellation request was
-#'   definitely successful (task was awaiting execution and has been discarded),
-#'   \code{NA} if a cancellation request was successfully sent (task was in
-#'   execution, and will be interrupted), and \code{FALSE} if already completed
-#'   or previously cancelled. Will always return \code{FALSE} if not using
-#'   dispatcher.
+#' @return Logical \code{TRUE} if the cancellation request was successful (was
+#'   awaiting execution or in execution), or else \code{FALSE} (if already
+#'   completed or previously cancelled). Will always return \code{FALSE} if not
+#'   using dispatcher.
 #'
 #' @examples
 #' if (interactive()) {

tests/tests.R

@@ -274,7 +274,7 @@ connection && Sys.getenv("NOT_CRAN") == "true" && {
   m2 <- mirai({ Sys.sleep(1); res <<- "m2 done" })
   Sys.sleep(0.1)
   test_true(stop_mirai(m2))
-  test_true(is.na(stop_mirai(m1)))
+  test_true(stop_mirai(m1))
   test_equal(m2$data, 20L)
   test_equal(m1$data, 20L)
   test_class("errorValue", mirai(res)[])