Standalone Activity

chasm/context.go

@@ -21,6 +21,7 @@ type Context interface {
 	// Intent() OperationIntent
 	// ComponentOptions(Component) []ComponentOption
 
+	structuredRef(Component) (ComponentRef, error)
 	getContext() context.Context
 }
 
@@ -94,6 +95,10 @@ func (c *immutableCtx) Ref(component Component) ([]byte, error) {
 	return c.root.Ref(component)
 }
 
+func (c *immutableCtx) structuredRef(component Component) (ComponentRef, error) {
+	return c.root.structuredRef(component)
+}
+
 func (c *immutableCtx) Now(component Component) time.Time {
 	return c.root.Now(component)
 }

chasm/context_mock.go

@@ -31,6 +31,10 @@ func (c *MockContext) Ref(cmp Component) ([]byte, error) {
 	return nil, nil
 }
 
+func (c *MockContext) structuredRef(cmp Component) (ComponentRef, error) {
+	return ComponentRef{}, nil
+}
+
 func (c *MockContext) ExecutionKey() ExecutionKey {
 	if c.HandleExecutionKey != nil {
 		return c.HandleExecutionKey()

chasm/engine.go

@@ -42,10 +42,12 @@ type Engine interface {
 	PollComponent(
 		context.Context,
 		ComponentRef,
-		func(Context, Component) (any, bool, error),
-		func(MutableContext, Component, any) error,
+		func(Context, Component) (bool, error),
 		...TransitionOption,
 	) ([]byte, error)
+
+	// NotifyExecution notifies any PollComponent callers waiting on the execution.
+	NotifyExecution(ExecutionKey)
 }
 
 type BusinessIDReusePolicy int
@@ -178,6 +180,9 @@ func UpdateWithNewExecution[C Component, I any, O1 any, O2 any](
 //   - consider remove ComponentRef from the return value and allow components to get
 //     the ref in the transition function. There are some caveats there, check the
 //     comment of the NewRef method in MutableContext.
+//
+// UpdateComponent applies updateFn to the component identified by the supplied component reference.
+// It returns the result, along with the new component reference. opts are currently ignored.
 func UpdateComponent[C any, R []byte | ComponentRef, I any, O any](
 	ctx context.Context,
 	r R,
@@ -209,6 +214,8 @@ func UpdateComponent[C any, R []byte | ComponentRef, I any, O any](
 	return output, newSerializedRef, err
 }
 
+// ReadComponent returns the result of evaluating readFn against the component identified by the
+// component reference. opts are currently ignored.
 func ReadComponent[C any, R []byte | ComponentRef, I any, O any](
 	ctx context.Context,
 	r R,
@@ -236,11 +243,18 @@ func ReadComponent[C any, R []byte | ComponentRef, I any, O any](
 	return output, err
 }
 
-func PollComponent[C any, R []byte | ComponentRef, I any, O any, T any](
+// PollComponent waits until the predicate is true when evaluated against the component identified
+// by the supplied component reference. If this times out due to a server-imposed long-poll timeout
+// then it returns (nil, nil, nil), as an indication that the caller should continue long-polling.
+// Otherwise it returns (output, ref, err), where output is the output of the predicate function,
+// and ref is a component reference identifying the state at which the predicate was satisfied. The
+// predicate must be monotonic: if it returns true at execution state transition s then it must
+// return true at all transitions t > s. If the predicate is true at the outset then PollComponent
+// returns immediately. opts are currently ignored.
+func PollComponent[C any, R []byte | ComponentRef, I any, O any](
 	ctx context.Context,
 	r R,
-	predicateFn func(C, Context, I) (T, bool, error),
-	operationFn func(C, MutableContext, I, T) (O, error),
+	monotonicPredicate func(C, Context, I) (O, bool, error),
 	input I,
 	opts ...TransitionOption,
 ) (O, []byte, error) {
@@ -254,13 +268,12 @@ func PollComponent[C any, R []byte | ComponentRef, I any, O any, T any](
 	newSerializedRef, err := engineFromContext(ctx).PollComponent(
 		ctx,
 		ref,
-		func(ctx Context, c Component) (any, bool, error) {
-			return predicateFn(c.(C), ctx, input)
-		},
-		func(ctx MutableContext, c Component, t any) error {
-			var err error
-			output, err = operationFn(c.(C), ctx, input, t.(T))
-			return err
+		func(ctx Context, c Component) (bool, error) {
+			out, satisfied, err := monotonicPredicate(c.(C), ctx, input)
+			if satisfied {
+				output = out
+			}
+			return satisfied, err
 		},
 		opts...,
 	)