Move multierror logic into luci-go.

common/errors/multierror_test.go

Index: common/errors/multierror_test.go
diff --git a/common/errors/multierror_test.go b/common/errors/multierror_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..a7a15329e1f430accde5798033af90a1a3d0b129
--- /dev/null
+++ b/common/errors/multierror_test.go
@@ -0,0 +1,138 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package errors
+
+import (
+	"errors"
+	"sync"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+type otherMEType []error
+
+func (o otherMEType) Error() string { return "FAIL" }
+
+func TestUpstreamErrors(t *testing.T) {
+	t.Parallel()
+
+	Convey("Test MultiError", t, func() {
+		Convey("nil", func() {
+			me := MultiError(nil)
+			So(me.Error(), ShouldEqual, "(0 errors)")
+			Convey("single", func() {
+				So(SingleError(error(me)), ShouldBeNil)
+			})
+		})
+		Convey("one", func() {
+			me := MultiError{errors.New("sup")}
+			So(me.Error(), ShouldEqual, "sup")
+		})
+		Convey("two", func() {
+			me := MultiError{errors.New("sup"), errors.New("what")}
+			So(me.Error(), ShouldEqual, "sup (and 1 other error)")
+		})
+		Convey("more", func() {
+			me := MultiError{errors.New("sup"), errors.New("what"), errors.New("nerds")}
+			So(me.Error(), ShouldEqual, "sup (and 2 other errors)")
+
+			Convey("single", func() {
+				So(SingleError(error(me)), ShouldResemble, errors.New("sup"))
+			})
+		})
+	})
+
+	Convey("SingleError passes through", t, func() {
+		e := errors.New("unique")
+		So(SingleError(e), ShouldEqual, e)
+	})
+
+	Convey("Test MultiError Conversion", t, func() {
+		ome := otherMEType{errors.New("sup")}
+		So(Fix(ome), ShouldHaveSameTypeAs, MultiError{})
+	})
+
+	Convey("Fix passes through", t, func() {
+		e := errors.New("unique")
+		So(Fix(e), ShouldEqual, e)
+	})
+}
+
+func TestLazyMultiError(t *testing.T) {
+	t.Parallel()
+
+	Convey("Test LazyMultiError", t, func() {
+		lme := LazyMultiError{Size: 10}
+		So(lme.Get(), ShouldEqual, nil)
+
+		e := errors.New("sup")
+		lme.Assign(6, e)
+		So(lme.Get(), ShouldResemble,
+			MultiError{nil, nil, nil, nil, nil, nil, e, nil, nil, nil})
+
+		lme.Assign(2, e)
+		So(lme.Get(), ShouldResemble,
+			MultiError{nil, nil, e, nil, nil, nil, e, nil, nil, nil})
+
+		So(func() { lme.Assign(20, e) }, ShouldPanic)
+
+		Convey("Try to freak out the race detector", func() {
+			lme := LazyMultiError{Size: 64}
+			Convey("all nils", func() {
+				wg := sync.WaitGroup{}
+				for i := 0; i < 64; i++ {
+					wg.Add(1)
+					go func(i int) {
+						lme.Assign(i, nil)
+						wg.Done()
+					}(i)
+				}
+				wg.Wait()
+				So(lme.Get(), ShouldBeNil)
+			})
+			Convey("every other", func() {
+				wow := errors.New("wow")
+				wg := sync.WaitGroup{}
+				for i := 0; i < 64; i++ {
+					wg.Add(1)
+					go func(i int) {
+						e := error(nil)
+						if i&1 == 1 {
+							e = wow
+						}
+						lme.Assign(i, e)
+						wg.Done()
+					}(i)
+				}
+				wg.Wait()
+				me := make(MultiError, 64)
+				for i := range me {
+					if i&1 == 1 {
+						me[i] = wow
+					}
+				}
+				So(lme.Get(), ShouldResemble, me)
+			})
+			Convey("all", func() {
+				wow := errors.New("wow")
+				wg := sync.WaitGroup{}
+				for i := 0; i < 64; i++ {
+					wg.Add(1)
+					go func(i int) {
+						lme.Assign(i, wow)
+						wg.Done()
+					}(i)
+				}
+				wg.Wait()
+				me := make(MultiError, 64)
+				for i := range me {
+					me[i] = wow
+				}
+				So(lme.Get(), ShouldResemble, me)
+			})
+		})
+	})
+}