add IO generator supporting error propagation

iters/ioit/ioit.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2023 individual contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ioit
+
+import (
+	"sync/atomic"
+
+	"github.com/0x5a17ed/itkit/iters/genit"
+)
+
+type GeneratorFn[T any] func(yield func(T)) error
+
+type Generator[T any] struct {
+	*genit.Generator[T]
+
+	err atomic.Pointer[error]
+}
+
+// Close stops the generator and returns any error returned by
+// the [GeneratorFn] function.
+func (g *Generator[T]) Close() error {
+	g.Generator.Stop()
+	return g.Err()
+}
+
+// Err returns any error returned by the [GeneratorFn] function.
+func (g *Generator[T]) Err() error {
+	if err := g.err.Load(); err != nil {
+		return *err
+	}
+	return nil
+}
+
+func Run[T any](fn GeneratorFn[T]) *Generator[T] {
+	iog := &Generator[T]{}
+
+	iog.Generator = genit.Run(func(yield func(T)) {
+		err := fn(yield)
+		iog.err.Store(&err)
+	})
+
+	return iog
+}

iters/ioit/ioit_test.go

@@ -0,0 +1,40 @@
+// Copyright (c) 2023 individual contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ioit_test
+
+import (
+	"io/fs"
+	"testing"
+
+	"github.com/0x5a17ed/itkit/iters/ioit"
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/goleak"
+)
+
+func TestGenerator_Err(t *testing.T) {
+	defer goleak.VerifyNone(t)
+
+	asserter := assert.New(t)
+
+	g := ioit.Run(func(func(any)) error {
+		return fs.ErrNotExist
+	})
+
+	asserter.NoError(g.Err())
+
+	asserter.False(g.Next())
+
+	asserter.ErrorIs(g.Err(), fs.ErrNotExist)
+}