Prepare for a type-safe OnceKey

Add an opaque OnceKey type and use it for all calls to Once in
build/soong.  A future patch will convert the arguments to
Once* to OnceKey once users outside build/soong have been updated.

Test: onceper_test.go
Change-Id: Ifcb338e6e603e804e507203c9508d30ffb2df966

1 files changed, 135 insertions, 0 deletions

diff --git a/android/onceper_test.go b/android/onceper_test.go
new file mode 100644
index 000000000..d2ca9ad70
--- /dev/null
+++ b/android/onceper_test.go
@@ -0,0 +1,135 @@
+// Copyright 2019 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+import (
+	"testing"
+)
+
+func TestOncePer_Once(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	a := once.Once(key, func() interface{} { return "a" }).(string)
+	b := once.Once(key, func() interface{} { return "b" }).(string)
+
+	if a != "a" {
+		t.Errorf(`first call to Once should return "a": %q`, a)
+	}
+
+	if b != "a" {
+		t.Errorf(`second call to Once with the same key should return "a": %q`, b)
+	}
+}
+
+func TestOncePer_Get(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	a := once.Once(key, func() interface{} { return "a" }).(string)
+	b := once.Get(key).(string)
+
+	if a != "a" {
+		t.Errorf(`first call to Once should return "a": %q`, a)
+	}
+
+	if b != "a" {
+		t.Errorf(`Get with the same key should return "a": %q`, b)
+	}
+}
+
+func TestOncePer_Get_panic(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	defer func() {
+		p := recover()
+
+		if p == nil {
+			t.Error("call to Get for unused key should panic")
+		}
+	}()
+
+	once.Get(key)
+}
+
+func TestOncePer_OnceStringSlice(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	a := once.OnceStringSlice(key, func() []string { return []string{"a"} })
+	b := once.OnceStringSlice(key, func() []string { return []string{"a"} })
+
+	if a[0] != "a" {
+		t.Errorf(`first call to OnceStringSlice should return ["a"]: %q`, a)
+	}
+
+	if b[0] != "a" {
+		t.Errorf(`second call to OnceStringSlice with the same key should return ["a"]: %q`, b)
+	}
+}
+
+func TestOncePer_Once2StringSlice(t *testing.T) {
+	once := OncePer{}
+	key := NewOnceKey("key")
+
+	a, b := once.Once2StringSlice(key, func() ([]string, []string) { return []string{"a"}, []string{"b"} })
+	c, d := once.Once2StringSlice(key, func() ([]string, []string) { return []string{"c"}, []string{"d"} })
+
+	if a[0] != "a" || b[0] != "b" {
+		t.Errorf(`first call to Once2StringSlice should return ["a"], ["b"]: %q, %q`, a, b)
+	}
+
+	if c[0] != "a" || d[0] != "b" {
+		t.Errorf(`second call to Once2StringSlice with the same key should return ["a"], ["b"]: %q, %q`, c, d)
+	}
+}
+
+func TestNewOnceKey(t *testing.T) {
+	once := OncePer{}
+	key1 := NewOnceKey("key")
+	key2 := NewOnceKey("key")
+
+	a := once.Once(key1, func() interface{} { return "a" }).(string)
+	b := once.Once(key2, func() interface{} { return "b" }).(string)
+
+	if a != "a" {
+		t.Errorf(`first call to Once should return "a": %q`, a)
+	}
+
+	if b != "b" {
+		t.Errorf(`second call to Once with the NewOnceKey from same string should return "b": %q`, b)
+	}
+}
+
+func TestNewCustomOnceKey(t *testing.T) {
+	type key struct {
+		key string
+	}
+	once := OncePer{}
+	key1 := NewCustomOnceKey(key{"key"})
+	key2 := NewCustomOnceKey(key{"key"})
+
+	a := once.Once(key1, func() interface{} { return "a" }).(string)
+	b := once.Once(key2, func() interface{} { return "b" }).(string)
+
+	if a != "a" {
+		t.Errorf(`first call to Once should return "a": %q`, a)
+	}
+
+	if b != "a" {
+		t.Errorf(`second call to Once with the NewCustomOnceKey from equal key should return "a": %q`, b)
+	}
+}