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plastikfanplastikfan
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feat(rx): add first/first-or-default operators (#176)
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3 files changed

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3 files changed

+221
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‎rx/observable-operator-first_test.go

Lines changed: 135 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,135 @@
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package rx_test
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import (
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"context"
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"github.com/fortytw2/leaktest"
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. "github.com/onsi/ginkgo/v2" //nolint:revive // ginkgo ok
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"github.com/snivilised/lorax/rx"
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)
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var _ = Describe("Observable operator", func() {
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Context("First", func() {
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When("not empty", func() {
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It("🧪 should: return first item", func() {
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// rxgo: Test_Observable_First_NotEmpty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := testObservable[int](ctx, 1, 2, 3).First()
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 1,
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})
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})
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})
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When("empty", func() {
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It("🧪 should: return nothing", func() {
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// rxgo: Test_Observable_First_Empty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := rx.Empty[int]().First()
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rx.Assert(ctx, obs, rx.IsEmpty[int]{})
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})
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})
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Context("Parallel", func() {
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When("not empty", func() {
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It("🧪 should: return first item", func() {
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// rxgo: Test_Observable_First_Parallel_NotEmpty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := testObservable[int](ctx, 1, 2, 3).First(rx.WithCPUPool[int]())
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 1,
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})
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})
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})
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When("empty", func() {
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It("🧪 should: return nothing", func() {
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// rxgo: Test_Observable_First_Parallel_Empty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := rx.Empty[int]().First(rx.WithCPUPool[int]())
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rx.Assert(ctx, obs, rx.IsEmpty[int]{})
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})
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})
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})
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})
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Context("FirstOrDefault", func() {
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When("not empty", func() {
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It("🧪 should: return first item", func() {
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// rxgo: Test_Observable_First_NotEmpty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := testObservable[int](ctx, 1, 2, 3).FirstOrDefault(10)
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 1,
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})
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})
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})
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When("empty", func() {
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It("🧪 should: return default", func() {
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// rxgo: Test_Observable_First_Empty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := rx.Empty[int]().FirstOrDefault(10)
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 10,
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})
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})
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})
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Context("Parallel", func() {
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When("not empty", func() {
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It("🧪 should: return first item", func() {
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// rxgo: Test_Observable_First_Parallel_NotEmpty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := testObservable[int](ctx, 1, 2, 3).FirstOrDefault(10, rx.WithCPUPool[int]())
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 1,
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})
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})
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})
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When("empty", func() {
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It("🧪 should: return default ", func() {
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// rxgo: Test_Observable_First_Parallel_Empty
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defer leaktest.Check(GinkgoT())()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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obs := rx.Empty[int]().FirstOrDefault(10, rx.WithCPUPool[int]())
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rx.Assert(ctx, obs, rx.HasItem[int]{
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Expected: 10,
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})
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})
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})
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})
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})
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})

‎rx/observable-operator.go

Lines changed: 84 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -746,6 +746,90 @@ func (op *findOperator[T]) gatherNext(_ context.Context, _ Item[T],
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_ chan<- Item[T], _ operatorOptions[T]) {
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}
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// First returns new Observable which emit only first item.
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// Cannot be run in parallel.
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func (o *ObservableImpl[T]) First(opts ...Option[T]) OptionalSingle[T] {
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const (
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forceSeq = true
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bypassGather = false
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)
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return optionalSingle(o.parent, o, func() operator[T] {
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return &firstOperator[T]{}
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}, forceSeq, bypassGather, opts...)
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}
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type firstOperator[T any] struct{}
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func (op *firstOperator[T]) next(ctx context.Context, item Item[T],
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dst chan<- Item[T], operatorOptions operatorOptions[T],
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) {
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item.SendContext(ctx, dst)
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operatorOptions.stop()
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}
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func (op *firstOperator[T]) err(ctx context.Context, item Item[T],
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dst chan<- Item[T], operatorOptions operatorOptions[T],
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) {
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defaultErrorFuncOperator(ctx, item, dst, operatorOptions)
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}
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func (op *firstOperator[T]) end(_ context.Context, _ chan<- Item[T]) {
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}
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func (op *firstOperator[T]) gatherNext(_ context.Context, _ Item[T],
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_ chan<- Item[T], _ operatorOptions[T],
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) {
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}
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// FirstOrDefault returns new Observable which emit only first item.
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// If the observable fails to emit any items, it emits a default value.
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// Cannot be run in parallel.
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func (o *ObservableImpl[T]) FirstOrDefault(defaultValue T, opts ...Option[T]) Single[T] {
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const (
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forceSeq = true
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bypassGather = false
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)
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return single(o.parent, o, func() operator[T] {
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return &firstOrDefaultOperator[T]{
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defaultValue: defaultValue,
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}
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}, forceSeq, bypassGather, opts...)
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}
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type firstOrDefaultOperator[T any] struct {
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defaultValue T
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sent bool
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}
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func (op *firstOrDefaultOperator[T]) next(ctx context.Context, item Item[T],
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dst chan<- Item[T], operatorOptions operatorOptions[T],
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) {
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item.SendContext(ctx, dst)
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op.sent = true
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operatorOptions.stop()
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}
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func (op *firstOrDefaultOperator[T]) err(ctx context.Context, item Item[T],
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dst chan<- Item[T], operatorOptions operatorOptions[T],
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) {
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defaultErrorFuncOperator(ctx, item, dst, operatorOptions)
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}
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func (op *firstOrDefaultOperator[T]) end(ctx context.Context, dst chan<- Item[T]) {
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if !op.sent {
824+
Of(op.defaultValue).SendContext(ctx, dst)
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}
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}
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func (op *firstOrDefaultOperator[T]) gatherNext(_ context.Context, _ Item[T],
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_ chan<- Item[T], _ operatorOptions[T],
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) {
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}
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// !!!
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// Max determines and emits the maximum-valued item emitted by an Observable according to a comparator.

‎rx/observable.go

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Original file line numberDiff line numberDiff line change
@@ -28,6 +28,8 @@ type Observable[T any] interface {
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Errors(opts ...Option[T]) []error
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Filter(apply Predicate[T], opts ...Option[T]) Observable[T]
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Find(find Predicate[T], opts ...Option[T]) OptionalSingle[T]
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First(opts ...Option[T]) OptionalSingle[T]
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FirstOrDefault(defaultValue T, opts ...Option[T]) Single[T]
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Max(comparator Comparator[T], initLimit InitLimit[T], opts ...Option[T]) OptionalSingle[T]
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Map(apply Func[T], opts ...Option[T]) Observable[T]
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Min(comparator Comparator[T], initLimit InitLimit[T], opts ...Option[T]) OptionalSingle[T]

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