blob: add ListIterator.All, a Go 1.23 iterator (#3608)

Author: vangent

blob/blob.go

@@ -70,6 +70,7 @@ import (
 	"fmt"
 	"hash"
 	"io"
+	"iter"
 	"log"
 	"mime"
 	"net/http"
@@ -611,6 +612,28 @@ func (i *ListIterator) Next(ctx context.Context) (*ListObject, error) {
 	return i.Next(ctx)
 }
 
+// All iterates over the iterator, returning a *ListObject and a download function for each entry.
+func (i *ListIterator) All(ctx context.Context, err *error) iter.Seq2[*ListObject, func(io.Writer, *ReaderOptions) error] {
+	return func(yield func(*ListObject, func(io.Writer, *ReaderOptions) error) bool) {
+		for {
+			obj, itErr := i.Next(ctx)
+			if itErr == io.EOF {
+				return
+			}
+			if itErr != nil {
+				*err = itErr
+				return
+			}
+			downloadFunc := func(w io.Writer, opts *ReaderOptions) error {
+				return i.b.Download(ctx, obj.Key, w, opts)
+			}
+			if !yield(obj, downloadFunc) {
+				return
+			}
+		}
+	}
+}
+
 // ListObject represents a single blob returned from List.
 type ListObject struct {
 	// Key is the key for this blob.

blob/blob_iter_test.go

@@ -0,0 +1,46 @@
+package blob_test
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"gocloud.dev/blob/memblob"
+)
+
+// Verify ListIterator.All.
+func TestListIterator_All(t *testing.T) {
+	ctx := context.Background()
+	b := memblob.OpenBucket(nil)
+	defer b.Close()
+
+	// Initialize the bucket with some keys.
+	want := map[string]string{}
+	for _, key := range []string{"a", "b", "c"} {
+		contents := fmt.Sprintf("%s-contents", key)
+		if err := b.WriteAll(ctx, key, []byte(contents), nil); err != nil {
+			t.Fatalf("failed to initialize key %q: %v", key, err)
+		}
+		want[key] = contents
+	}
+
+	// Iterate over the bucket using iter.All.
+	var err error
+	got := map[string]string{}
+	iter := b.List(nil)
+	for obj, download := range iter.All(ctx, &err) {
+		var buf bytes.Buffer
+		if dErr := download(&buf, nil); dErr != nil {
+			t.Errorf("failed to download %q: %v", obj.Key, dErr)
+		}
+		got[obj.Key] = string(buf.Bytes())
+	}
+	if err != nil {
+		t.Fatalf("iteration failed: %v", err)
+	}
+	if diff := cmp.Diff(got, want); diff != "" {
+		t.Errorf("got %v, want %v, diff %s", got, want, diff)
+	}
+}

blob/example_test.go

@@ -15,6 +15,7 @@
 package blob_test
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"io"
@@ -219,12 +220,29 @@ func ExampleBucket_List() {
 		fmt.Println(obj.Key)
 	}
 
+	// Alternatively, use All to iterate (and optionally download):
+	fmt.Println()
+	fmt.Println("Now, using an iterator:")
+	iter = bucket.List(nil)
+	for obj, download := range iter.All(ctx, &err) {
+		var buf bytes.Buffer
+		_ = download(&buf, nil) // ignore error and use default ReaderOptions
+		fmt.Printf("%s: %s\n", obj.Key, string(buf.Bytes()))
+	}
+
 	// Output:
 	// foo0.txt
 	// foo1.txt
 	// foo2.txt
 	// foo3.txt
 	// foo4.txt
+	//
+	// Now, using an iterator:
+	// foo0.txt: Go Cloud Development Kit
+	// foo1.txt: Go Cloud Development Kit
+	// foo2.txt: Go Cloud Development Kit
+	// foo3.txt: Go Cloud Development Kit
+	// foo4.txt: Go Cloud Development Kit
 }
 
 func ExampleBucket_List_withDelimiter() {