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tanaka0722-devtanaka0722-dev
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Add WithFailFast() (#118)
In sourcegraph/conc#104, a "FailFast" option is likely going to be added to iterators that, on error, stops running additional tasks and returns the error that caused the first failure. "FailFast" seems is a pretty standard description for this behavior, and combining two common options into a single option with a more discoverable name seems like a nice thing to do before 1.0.
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4 files changed

Lines changed: 37 additions & 2 deletions

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‎pool/context_pool.go‎

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@@ -81,6 +81,16 @@ func (p *ContextPool) WithCancelOnError() *ContextPool {
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return p
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}
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// WithFailFast is an alias for the combination of WithFirstError and
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// WithCancelOnError. By default, the errors from all tasks are returned and
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// the pool's context is not canceled until the parent context is canceled.
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func (p *ContextPool) WithFailFast() *ContextPool {
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p.panicIfInitialized()
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p.WithFirstError()
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p.WithCancelOnError()
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return p
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}
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// WithMaxGoroutines limits the number of goroutines in a pool.
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// Defaults to unlimited. Panics if n < 1.
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func (p *ContextPool) WithMaxGoroutines(n int) *ContextPool {

‎pool/context_pool_test.go‎

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@@ -187,9 +187,9 @@ func TestContextPool(t *testing.T) {
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require.NotErrorIs(t, err, err2)
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})
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t.Run("WithFirstError and WithCancelOnError", func(t *testing.T) {
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t.Run("WithFailFast", func(t *testing.T) {
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t.Parallel()
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p := New().WithContext(bgctx).WithFirstError().WithCancelOnError()
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p := New().WithContext(bgctx).WithFailFast()
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p.Go(func(ctx context.Context) error {
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return err1
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})

‎pool/result_context_pool.go‎

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@@ -62,6 +62,15 @@ func (p *ResultContextPool[T]) WithCancelOnError() *ResultContextPool[T] {
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return p
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}
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// WithFailFast is an alias for the combination of WithFirstError and
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// WithCancelOnError. By default, the errors from all tasks are returned and
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// the pool's context is not canceled until the parent context is canceled.
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func (p *ResultContextPool[T]) WithFailFast() *ResultContextPool[T] {
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p.panicIfInitialized()
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p.contextPool.WithFailFast()
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return p
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}
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// WithMaxGoroutines limits the number of goroutines in a pool.
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// Defaults to unlimited. Panics if n < 1.
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func (p *ResultContextPool[T]) WithMaxGoroutines(n int) *ResultContextPool[T] {

‎pool/result_context_pool_test.go‎

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Original file line numberDiff line numberDiff line change
@@ -101,6 +101,22 @@ func TestResultContextPool(t *testing.T) {
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require.ErrorIs(t, err, err1)
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})
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t.Run("WithFailFast", func(t *testing.T) {
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t.Parallel()
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p := NewWithResults[int]().WithContext(context.Background()).WithFailFast()
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p.Go(func(ctx context.Context) (int, error) {
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return 0, err1
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})
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p.Go(func(ctx context.Context) (int, error) {
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<-ctx.Done()
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return 1, ctx.Err()
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})
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results, err := p.Wait()
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require.ErrorIs(t, err, err1)
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require.NotErrorIs(t, err, context.Canceled)
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require.Empty(t, results)
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})
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t.Run("WithCancelOnError and panic", func(t *testing.T) {
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t.Parallel()
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p := NewWithResults[int]().

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