context: provide String methods. The Strings show the functions called
to construct the context left-to-right. External implementations of the
Context interface may break the chain, but establishing this pattern now
may encourage them to do the right thing.
LGTM=bcmills
R=bcmills
CC=golang-codereviews
https://golang.org/cl/116430044
diff --git a/context/context.go b/context/context.go
index ffbdd83..554e14d 100644
--- a/context/context.go
+++ b/context/context.go
@@ -38,6 +38,7 @@
import (
"errors"
+ "fmt"
"sync"
"time"
)
@@ -289,6 +290,10 @@
return c.err
}
+func (c *cancelCtx) String() string {
+ return fmt.Sprintf("%v.WithCancel", c.Context)
+}
+
// cancel closes c.done, cancels each of c's children, and, if
// removeFromParent is true, removes c from its parent's children.
func (c *cancelCtx) cancel(removeFromParent bool, err error) {
@@ -369,6 +374,10 @@
return c.deadline, true
}
+func (c *timerCtx) String() string {
+ return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, c.deadline.Sub(time.Now()))
+}
+
func (c *timerCtx) cancel(removeFromParent bool, err error) {
c.cancelCtx.cancel(removeFromParent, err)
c.mu.Lock()
@@ -410,6 +419,10 @@
key, val interface{}
}
+func (c *valueCtx) String() string {
+ return fmt.Sprintf("%v.WithValue(%#v, %#v)", c.Context, c.key, c.val)
+}
+
func (c *valueCtx) Value(key interface{}) interface{} {
if c.key == key {
return c.val
diff --git a/context/context_test.go b/context/context_test.go
index 2342a86..c1a4de5 100644
--- a/context/context_test.go
+++ b/context/context_test.go
@@ -8,6 +8,7 @@
"fmt"
"math/rand"
"runtime"
+ "strings"
"sync"
"testing"
"time"
@@ -30,8 +31,8 @@
t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
default:
}
- if s := fmt.Sprint(c); s != "context.Background" {
- t.Errorf(`Background.String = %q want "context.Background"`, s)
+ if got, want := fmt.Sprint(c), "context.Background"; got != want {
+ t.Errorf("Background().String() = %q want %q", got, want)
}
}
@@ -45,13 +46,18 @@
t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
default:
}
- if s := fmt.Sprint(c); s != "context.TODO" {
- t.Errorf(`TODO.String = %q want "context.TODO"`, s)
+ if got, want := fmt.Sprint(c), "context.TODO"; got != want {
+ t.Errorf("TODO().String() = %q want %q", got, want)
}
}
func TestWithCancel(t *testing.T) {
c1, cancel := WithCancel(Background())
+
+ if got, want := fmt.Sprint(c1), "context.Background.WithCancel"; got != want {
+ t.Errorf("c1.String() = %q want %q", got, want)
+ }
+
o := otherContext{c1}
c2, _ := WithCancel(o)
contexts := []Context{c1, o, c2}
@@ -72,7 +78,7 @@
}
cancel()
- time.Sleep(100 * time.Millisecond) // let cancellation propagate
+ time.Sleep(100 * time.Millisecond) // let cancelation propagate
for i, c := range contexts {
select {
@@ -236,6 +242,9 @@
func TestDeadline(t *testing.T) {
c, _ := WithDeadline(Background(), time.Now().Add(100*time.Millisecond))
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
testDeadline(c, 200*time.Millisecond, t)
c, _ = WithDeadline(Background(), time.Now().Add(100*time.Millisecond))
@@ -250,6 +259,9 @@
func TestTimeout(t *testing.T) {
c, _ := WithTimeout(Background(), 100*time.Millisecond)
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
testDeadline(c, 200*time.Millisecond, t)
c, _ = WithTimeout(Background(), 100*time.Millisecond)
@@ -262,12 +274,12 @@
testDeadline(c, 200*time.Millisecond, t)
}
-func TestCancelledTimeout(t *testing.T) {
+func TestCanceledTimeout(t *testing.T) {
c, _ := WithTimeout(Background(), 200*time.Millisecond)
o := otherContext{c}
c, cancel := WithTimeout(o, 400*time.Millisecond)
cancel()
- time.Sleep(100 * time.Millisecond) // let cancellation propagate
+ time.Sleep(100 * time.Millisecond) // let cancelation propagate
select {
case <-c.Done():
default:
@@ -304,6 +316,10 @@
c1 := WithValue(Background(), k1, "c1k1")
check(c1, "c1", "c1k1", "", "")
+ if got, want := fmt.Sprint(c1), `context.Background.WithValue(1, "c1k1")`; got != want {
+ t.Errorf("c.String() = %q want %q", got, want)
+ }
+
c2 := WithValue(c1, k2, "c2k2")
check(c2, "c2", "c1k1", "c2k2", "")
@@ -487,17 +503,14 @@
switch rand.Intn(3) {
case 0:
v := new(value)
- t.Logf("WithValue(%p, %p)", v, v)
ctx = WithValue(ctx, v, v)
vals = append(vals, v)
case 1:
var cancel CancelFunc
- t.Logf("WithCancel")
ctx, cancel = WithCancel(ctx)
cancels = append(cancels, cancel)
case 2:
var cancel CancelFunc
- t.Logf("WithTimeout")
ctx, cancel = WithTimeout(ctx, timeout)
cancels = append(cancels, cancel)
numTimers++
@@ -515,6 +528,10 @@
errorf("ctx should not be canceled yet")
default:
}
+ if s, prefix := fmt.Sprint(ctx), "context.Background."; !strings.HasPrefix(s, prefix) {
+ t.Errorf("ctx.String() = %q want prefix %q", s, prefix)
+ }
+ t.Log(ctx)
checkValues("before cancel")
if testTimeout {
select {
