1 files changed, 11 insertions, 5 deletions

diff --git a/android/onceper.go b/android/onceper.go
index 5ad17fa9..ff865c2e 100644
--- a/android/onceper.go
+++ b/android/onceper.go
@@ -40,7 +40,8 @@ func (once *OncePer) maybeWaitFor(key OnceKey, value interface{}) interface{} {
 }
 
 // Once computes a value the first time it is called with a given key per OncePer, and returns the
-// value without recomputing when called with the same key.  key must be hashable.
+// value without recomputing when called with the same key.  key must be hashable.  If value panics
+// the panic will be propagated but the next call to Once with the same key will return nil.
 func (once *OncePer) Once(key OnceKey, value func() interface{}) interface{} {
         // Fast path: check if the key is already in the map
         if v, ok := once.values.Load(key); ok {
@@ -54,10 +55,15 @@ func (once *OncePer) Once(key OnceKey, value func() interface{}) interface{} {
                 return once.maybeWaitFor(key, v)
         }
 
-        // The waiter is inserted, call the value constructor, store it, and signal the waiter
-        v := value()
-        once.values.Store(key, v)
-        close(waiter)
+        // The waiter is inserted, call the value constructor, store it, and signal the waiter.  Use defer in case
+        // the function panics.
+        var v interface{}
+        defer func() {
+                once.values.Store(key, v)
+                close(waiter)
+        }()
+
+        v = value()
 
         return v
 }