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feat: add WithoutCancel #200
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84a6c63
feat: add WithoutCancel
Reasno 75d23b3
fix: hound complaint
Reasno 3364f45
fix: WithoutCancel should panic when parent is nil
GGXXLL 0283f36
fix: tests
GGXXLL 717767d
fix: naked return is not good for readability
GGXXLL 650b685
chore: surpress linter
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,43 @@ | ||
package ctxmeta | ||
|
||
import ( | ||
"context" | ||
"time" | ||
) | ||
|
||
type asyncContext struct { | ||
ctx context.Context | ||
} | ||
|
||
func (a asyncContext) Deadline() (deadline time.Time, ok bool) { | ||
return time.Time{}, false | ||
} | ||
|
||
func (a asyncContext) Done() <-chan struct{} { | ||
return nil | ||
} | ||
|
||
func (a asyncContext) Err() error { | ||
return nil | ||
} | ||
|
||
func (a asyncContext) Value(key interface{}) interface{} { | ||
return a.ctx.Value(key) | ||
} | ||
|
||
// WithoutCancel creates a new context from an existing context and inherits all | ||
// values from the existing context. However if the existing context is | ||
// cancelled, timeouts or passes deadline, the returning context will not be | ||
// affected. This is useful in an async HTTP handler. When the http response is sent, | ||
// the request context will be cancelled. If you still want to access the value from request context (eg. tracing), | ||
// you can use: | ||
// func(request *http.Request, responseWriter http.ResponseWriter) { | ||
// go DoSomeSlowDatabaseOperation(WithoutCancel(request.Context())) | ||
// responseWriter.Write([]byte("ok")) | ||
// } | ||
func WithoutCancel(requestScopeContext context.Context) (valueOnlyContext context.Context) { | ||
if requestScopeContext == nil { | ||
panic("cannot create context from nil parent") | ||
} | ||
return asyncContext{requestScopeContext} | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,33 @@ | ||
package ctxmeta | ||
|
||
import ( | ||
"context" | ||
"testing" | ||
|
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"github.com/stretchr/testify/assert" | ||
) | ||
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func TestWithoutCancel(t *testing.T) { | ||
key := struct{}{} | ||
ctx := context.WithValue(context.Background(), key, "value") | ||
ctx, cancel := context.WithCancel(ctx) | ||
cancel() | ||
|
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select { | ||
case <-WithoutCancel(ctx).Done(): | ||
t.Fatal("context is cancelled") | ||
default: | ||
} | ||
|
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_, dead := WithoutCancel(ctx).Deadline() | ||
assert.False(t, dead) | ||
assert.Nil(t, WithoutCancel(ctx).Err()) | ||
assert.Equal(t, "value", WithoutCancel(ctx).Value(key)) | ||
} | ||
|
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func TestWithoutCancel_Nil(t *testing.T) { | ||
defer func() { | ||
assert.Equal(t, "cannot create context from nil parent", recover()) | ||
}() | ||
WithoutCancel(nil) //nolint | ||
} |
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what's the purpose of this change?