test(flow): improve coverage and minor refactoring

.github/workflows/build.yml

@@ -28,4 +28,6 @@ jobs:
 
     - name: Upload coverage to Codecov
       if: ${{ matrix.go-version == '1.18.x' }}
-      run: bash <(curl -s https://codecov.io/bash)
+      uses: codecov/codecov-action@v4
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}

.golangci.yml

@@ -40,3 +40,4 @@ issues:
         - errcheck
         - unparam
         - prealloc
+        - funlen

flow/batch.go

@@ -8,23 +8,25 @@ import (
 )
 
 // Batch processor breaks a stream of elements into batches based on size or timing.
-// When the maximum batch size is reached or the batch time is elapsed, and the current buffer
-// is not empty, a new batch will be emitted.
+// When the maximum batch size is reached or the batch time is elapsed, and the
+// current buffer is not empty, a new batch will be emitted.
 // Note: once a batch is sent downstream, the timer will be reset.
 // T indicates the incoming element type, and the outgoing element type is []T.
 type Batch[T any] struct {
 	maxBatchSize int
 	timeInterval time.Duration
 	in           chan any
 	out          chan any
+	buffer       []T
 }
 
 // Verify Batch satisfies the Flow interface.
 var _ streams.Flow = (*Batch[any])(nil)
 
-// NewBatch returns a new Batch operator using the specified maximum batch size and the
-// time interval.
+// NewBatch returns a new Batch operator using the specified maximum batch size and
+// the time interval.
 // T specifies the incoming element type, and the outgoing element type is []T.
+//
 // NewBatch will panic if the maxBatchSize argument is not positive.
 func NewBatch[T any](maxBatchSize int, timeInterval time.Duration) *Batch[T] {
 	if maxBatchSize < 1 {
@@ -35,7 +37,10 @@ func NewBatch[T any](maxBatchSize int, timeInterval time.Duration) *Batch[T] {
 		timeInterval: timeInterval,
 		in:           make(chan any),
 		out:          make(chan any),
+		buffer:       make([]T, 0, maxBatchSize),
 	}
+
+	// start stream processing
 	go batchFlow.batchStream()
 
 	return batchFlow
@@ -76,34 +81,37 @@ func (b *Batch[T]) batchStream() {
 	ticker := time.NewTicker(b.timeInterval)
 	defer ticker.Stop()
 
-	batch := make([]T, 0, b.maxBatchSize)
 	for {
 		select {
 		case element, ok := <-b.in:
 			if ok {
-				batch = append(batch, element.(T))
+				b.buffer = append(b.buffer, element.(T))
 				// dispatch the batch if the maximum batch size has been reached
-				if len(batch) >= b.maxBatchSize {
-					b.out <- batch
-					batch = make([]T, 0, b.maxBatchSize)
+				if len(b.buffer) >= b.maxBatchSize {
+					b.flush()
 				}
 				// reset the ticker
 				ticker.Reset(b.timeInterval)
 			} else {
 				// send the available buffer elements as a new batch, close the
 				// output channel and return
-				if len(batch) > 0 {
-					b.out <- batch
+				if len(b.buffer) > 0 {
+					b.flush()
 				}
 				close(b.out)
 				return
 			}
 		case <-ticker.C:
 			// timeout; dispatch and reset the buffer
-			if len(batch) > 0 {
-				b.out <- batch
-				batch = make([]T, 0, b.maxBatchSize)
+			if len(b.buffer) > 0 {
+				b.flush()
 			}
 		}
 	}
 }
+
+// flush sends the elements in the buffer downstream and resets the buffer.
+func (b *Batch[T]) flush() {
+	b.out <- b.buffer
+	b.buffer = make([]T, 0, b.maxBatchSize)
+}

flow/batch_test.go

@@ -31,14 +31,10 @@ func TestBatch(t *testing.T) {
 	go func() {
 		source.
 			Via(batch).
-			Via(flow.NewMap(retransmitStringSlice, 1)). // test generic return type
 			To(sink)
 	}()
 
-	var outputValues [][]string
-	for e := range sink.Out {
-		outputValues = append(outputValues, e.([]string))
-	}
+	outputValues := readSlice[[]string](sink.Out)
 	fmt.Println(outputValues)
 
 	assert.Equal(t, 3, len(outputValues)) // [[a b c d] [e f g] [h]]
@@ -48,7 +44,42 @@ func TestBatch(t *testing.T) {
 	assert.Equal(t, []string{"h"}, outputValues[2])
 }
 
-func TestBatchInvalidArguments(t *testing.T) {
+func TestBatch_Ptr(t *testing.T) {
+	in := make(chan any)
+	out := make(chan any)
+
+	source := ext.NewChanSource(in)
+	batch := flow.NewBatch[*string](4, 40*time.Millisecond)
+	sink := ext.NewChanSink(out)
+	assert.NotEqual(t, batch.Out(), nil)
+
+	inputValues := ptrSlice([]string{"a", "b", "c", "d", "e", "f", "g"})
+	go func() {
+		for _, e := range inputValues {
+			ingestDeferred(e, in, 5*time.Millisecond)
+		}
+	}()
+	go ingestDeferred(ptr("h"), in, 90*time.Millisecond)
+	go closeDeferred(in, 100*time.Millisecond)
+
+	go func() {
+		source.
+			Via(batch).
+			Via(flow.NewPassThrough()). // Via coverage
+			To(sink)
+	}()
+
+	outputValues := readSlice[[]*string](sink.Out)
+	fmt.Println(outputValues)
+
+	assert.Equal(t, 3, len(outputValues)) // [[a b c d] [e f g] [h]]
+
+	assert.Equal(t, ptrSlice([]string{"a", "b", "c", "d"}), outputValues[0])
+	assert.Equal(t, ptrSlice([]string{"e", "f", "g"}), outputValues[1])
+	assert.Equal(t, ptrSlice([]string{"h"}), outputValues[2])
+}
+
+func TestBatch_InvalidArguments(t *testing.T) {
 	assert.Panics(t, func() {
 		flow.NewBatch[string](0, time.Second)
 	})

flow/filter_test.go

@@ -0,0 +1,72 @@
+package flow_test
+
+import (
+	"testing"
+
+	"github.com/reugn/go-streams"
+	ext "github.com/reugn/go-streams/extension"
+	"github.com/reugn/go-streams/flow"
+	"github.com/reugn/go-streams/internal/assert"
+)
+
+func TestFilter(t *testing.T) {
+	tests := []struct {
+		name       string
+		filterFlow streams.Flow
+		ptr        bool
+	}{
+		{
+			name: "values",
+			filterFlow: flow.NewFilter(func(e int) bool {
+				return e%2 != 0
+			}, 1),
+			ptr: false,
+		},
+		{
+			name: "pointers",
+			filterFlow: flow.NewFilter(func(e *int) bool {
+				return *e%2 != 0
+			}, 1),
+			ptr: true,
+		},
+	}
+	input := []int{1, 2, 3, 4, 5}
+	expected := []int{1, 3, 5}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			in := make(chan any, 5)
+			out := make(chan any, 5)
+
+			source := ext.NewChanSource(in)
+			sink := ext.NewChanSink(out)
+
+			if tt.ptr {
+				ingestSlice(ptrSlice(input), in)
+			} else {
+				ingestSlice(input, in)
+			}
+			close(in)
+
+			source.
+				Via(tt.filterFlow).
+				To(sink)
+
+			if tt.ptr {
+				output := readSlicePtr[int](out)
+				assert.Equal(t, ptrSlice(expected), output)
+			} else {
+				output := readSlice[int](out)
+				assert.Equal(t, expected, output)
+			}
+		})
+	}
+}
+
+func TestFilter_NonPositiveParallelism(t *testing.T) {
+	assert.Panics(t, func() {
+		flow.NewFilter(filterNotContainsA, 0)
+	})
+	assert.Panics(t, func() {
+		flow.NewFilter(filterNotContainsA, -1)
+	})
+}

flow/flat_map_test.go

@@ -0,0 +1,94 @@
+package flow_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/reugn/go-streams"
+	ext "github.com/reugn/go-streams/extension"
+	"github.com/reugn/go-streams/flow"
+	"github.com/reugn/go-streams/internal/assert"
+)
+
+func TestFlatMap(t *testing.T) {
+	tests := []struct {
+		name        string
+		flatMapFlow streams.Flow
+		inPtr       bool
+		outPtr      bool
+	}{
+		{
+			name:  "val-val",
+			inPtr: false,
+			flatMapFlow: flow.NewFlatMap(func(in string) []string {
+				return []string{in, strings.ToUpper(in)}
+			}, 1),
+			outPtr: false,
+		},
+		{
+			name:  "ptr-val",
+			inPtr: true,
+			flatMapFlow: flow.NewFlatMap(func(in *string) []string {
+				return []string{*in, strings.ToUpper(*in)}
+			}, 1),
+			outPtr: false,
+		},
+		{
+			name:  "ptr-ptr",
+			inPtr: true,
+			flatMapFlow: flow.NewFlatMap(func(in *string) []*string {
+				upper := strings.ToUpper(*in)
+				return []*string{in, &upper}
+			}, 1),
+			outPtr: true,
+		},
+		{
+			name:  "val-ptr",
+			inPtr: false,
+			flatMapFlow: flow.NewFlatMap(func(in string) []*string {
+				upper := strings.ToUpper(in)
+				return []*string{&in, &upper}
+			}, 1),
+			outPtr: true,
+		},
+	}
+	input := []string{"a", "b", "c"}
+	expected := []string{"a", "A", "b", "B", "c", "C"}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			in := make(chan any, 3)
+			out := make(chan any, 6)
+
+			source := ext.NewChanSource(in)
+			sink := ext.NewChanSink(out)
+
+			if tt.inPtr {
+				ingestSlice(ptrSlice(input), in)
+			} else {
+				ingestSlice(input, in)
+			}
+			close(in)
+
+			source.
+				Via(tt.flatMapFlow).
+				To(sink)
+
+			if tt.outPtr {
+				output := readSlicePtr[string](out)
+				assert.Equal(t, ptrSlice(expected), output)
+			} else {
+				output := readSlice[string](out)
+				assert.Equal(t, expected, output)
+			}
+		})
+	}
+}
+
+func TestFlatMap_NonPositiveParallelism(t *testing.T) {
+	assert.Panics(t, func() {
+		flow.NewFlatMap(addAsterisk, 0)
+	})
+	assert.Panics(t, func() {
+		flow.NewFlatMap(addAsterisk, -1)
+	})
+}