From 4d18ef1fb9adcadf4ba0b02c6ecf9af87cda64be Mon Sep 17 00:00:00 2001
From: James Kleeh <james.kleeh@gmail.com>
Date: Wed, 21 Sep 2016 14:46:37 -0400
Subject: [PATCH] Fix synchronous promises being executed multiple times

---
 .../grails/async/factory/SynchronousPromise.groovy |  4 +++-
 .../async/SynchronousPromiseFactorySpec.groovy     | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/grails-async/src/main/groovy/org/grails/async/factory/SynchronousPromise.groovy b/grails-async/src/main/groovy/org/grails/async/factory/SynchronousPromise.groovy
index 92e72bc51f2..56d66c603be 100644
--- a/grails-async/src/main/groovy/org/grails/async/factory/SynchronousPromise.groovy
+++ b/grails-async/src/main/groovy/org/grails/async/factory/SynchronousPromise.groovy
@@ -30,6 +30,7 @@ import java.util.concurrent.TimeUnit
 class SynchronousPromise<T> implements Promise<T> {
     Closure<T> callable
     def value
+    boolean executed = false
 
     SynchronousPromise(Closure<T> callable) {
         this.callable = callable
@@ -51,7 +52,8 @@ class SynchronousPromise<T> implements Promise<T> {
     }
 
     T get() throws Throwable {
-        if (value == null) {
+        if (!executed) {
+            executed = true
             try {
                 value = callable.call()
             } catch (e) {
diff --git a/grails-async/src/test/groovy/grails/async/SynchronousPromiseFactorySpec.groovy b/grails-async/src/test/groovy/grails/async/SynchronousPromiseFactorySpec.groovy
index af93e97a85b..18a581d247f 100644
--- a/grails-async/src/test/groovy/grails/async/SynchronousPromiseFactorySpec.groovy
+++ b/grails-async/src/test/groovy/grails/async/SynchronousPromiseFactorySpec.groovy
@@ -156,4 +156,18 @@ class SynchronousPromiseFactorySpec extends Specification {
         then:'the closure is executed'
         1 * callable.call()
     }
+
+    @Issue("GRAILS-10152")
+    void "Test promise closure is not executed multiple times if it returns null"() {
+        given:
+        Closure callable =  Mock(Closure) {
+            call() >> null
+        }
+
+        when:"A promise is created"
+        Promises.waitAll([Promises.createPromise(callable), Promises.createPromise(callable)])
+
+        then:'the closure is executed twice'
+        2 * callable.call()
+    }
 }
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