Merge changes I7801fc7c,I7d407bd1

* changes:
  Add CopyOf utility method
  Fix a bug in OncePer.Get that could return a waiter

4 files changed, 82 insertions, 1 deletions

diff --git a/android/onceper.go b/android/onceper.go
index f06f428d..5ad17fa9 100644
--- a/android/onceper.go
+++ b/android/onceper.go
@@ -70,7 +70,7 @@ func (once *OncePer) Get(key OnceKey) interface{} {
 		panic(fmt.Errorf("Get() called before Once()"))
 	}
 
-	return v
+	return once.maybeWaitFor(key, v)
 }
 
 // OnceStringSlice is the same as Once, but returns the value cast to a []string
diff --git a/android/onceper_test.go b/android/onceper_test.go
index f27799be..95303baf 100644
--- a/android/onceper_test.go
+++ b/android/onceper_test.go
@@ -16,6 +16,7 @@ package android
 
 import (
 	"testing"
+	"time"
 )
 
 func TestOncePer_Once(t *testing.T) {
@@ -34,6 +35,21 @@ func TestOncePer_Once(t *testing.T) {
 	}
 }
 
+func TestOncePer_Once_wait(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	ch := make(chan bool)
+
+	go once.Once(key, func() interface{} { close(ch); time.Sleep(100 * time.Millisecond); return "foo" })
+	<-ch
+	a := once.Once(key, func() interface{} { return "bar" }).(string)
+
+	if a != "foo" {
+		t.Errorf("expect %q, got %q", "foo", a)
+	}
+}
+
 func TestOncePer_Get(t *testing.T) {
 	once := OncePer{}
 	key := NewOnceKey("key")
@@ -65,6 +81,21 @@ func TestOncePer_Get_panic(t *testing.T) {
 	once.Get(key)
 }
 
+func TestOncePer_Get_wait(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	ch := make(chan bool)
+
+	go once.Once(key, func() interface{} { close(ch); time.Sleep(100 * time.Millisecond); return "foo" })
+	<-ch
+	a := once.Get(key).(string)
+
+	if a != "foo" {
+		t.Errorf("expect %q, got %q", "foo", a)
+	}
+}
+
 func TestOncePer_OnceStringSlice(t *testing.T) {
 	once := OncePer{}
 	key := NewOnceKey("key")
diff --git a/android/util.go b/android/util.go
index 92ab845b..8fc159dc 100644
--- a/android/util.go
+++ b/android/util.go
@@ -20,6 +20,11 @@ import (
 	"strings"
 )
 
+// CopyOf returns a new slice that has the same contents as s.
+func CopyOf(s []string) []string {
+	return append([]string(nil), s...)
+}
+
 func JoinWithPrefix(strs []string, prefix string) string {
 	if len(strs) == 0 {
 		return ""
diff --git a/android/util_test.go b/android/util_test.go
index 1c791b24..2e5eb07e 100644
--- a/android/util_test.go
+++ b/android/util_test.go
@@ -15,6 +15,7 @@
 package android
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 )
@@ -359,3 +360,47 @@ func TestRemoveFromList(t *testing.T) {
 		})
 	}
 }
+
+func ExampleCopyOf() {
+	a := []string{"1", "2", "3"}
+	b := CopyOf(a)
+	a[0] = "-1"
+	fmt.Printf("a = %q\n", a)
+	fmt.Printf("b = %q\n", b)
+
+	// Output:
+	// a = ["-1" "2" "3"]
+	// b = ["1" "2" "3"]
+}
+
+func ExampleCopyOf_append() {
+	a := make([]string, 1, 2)
+	a[0] = "foo"
+
+	fmt.Println("Without CopyOf:")
+	b := append(a, "bar")
+	c := append(a, "baz")
+	fmt.Printf("a = %q\n", a)
+	fmt.Printf("b = %q\n", b)
+	fmt.Printf("c = %q\n", c)
+
+	a = make([]string, 1, 2)
+	a[0] = "foo"
+
+	fmt.Println("With CopyOf:")
+	b = append(CopyOf(a), "bar")
+	c = append(CopyOf(a), "baz")
+	fmt.Printf("a = %q\n", a)
+	fmt.Printf("b = %q\n", b)
+	fmt.Printf("c = %q\n", c)
+
+	// Output:
+	// Without CopyOf:
+	// a = ["foo"]
+	// b = ["foo" "baz"]
+	// c = ["foo" "baz"]
+	// With CopyOf:
+	// a = ["foo"]
+	// b = ["foo" "bar"]
+	// c = ["foo" "baz"]
+}