fix: discover handler errors for lint (#1677)

Signed-off-by: Terry Howe <[email protected]>

Author: TerryHowe

cmd/oras/internal/display/metadata/table/discover.go

@@ -55,21 +55,30 @@ func (h *discoverHandler) OnDiscovered(referrer, subject ocispec.Descriptor) err
 }
 
 // Render implements metadata.DiscoverHandler.
-func (h *discoverHandler) Render() error {
+func (h *discoverHandler) Render() (err error) {
 	if n := len(h.referrers); n != 1 {
-		fmt.Fprintln(h.out, "Discovered", n, "artifacts referencing", h.rawReference)
+		_, err = fmt.Fprintln(h.out, "Discovered", n, "artifacts referencing", h.rawReference)
 	} else {
-		fmt.Fprintln(h.out, "Discovered", n, "artifact referencing", h.rawReference)
+		_, err = fmt.Fprintln(h.out, "Discovered", n, "artifact referencing", h.rawReference)
+	}
+	if err != nil {
+		return err
+	}
+	_, err = fmt.Fprintln(h.out, "Digest:", h.root.Digest)
+	if err != nil {
+		return err
 	}
-	fmt.Fprintln(h.out, "Digest:", h.root.Digest)
 	if len(h.referrers) == 0 {
 		return nil
 	}
-	fmt.Fprintln(h.out)
+	_, err = fmt.Fprintln(h.out)
+	if err != nil {
+		return err
+	}
 	return h.printDiscoveredReferrersTable()
 }
 
-func (h *discoverHandler) printDiscoveredReferrersTable() error {
+func (h *discoverHandler) printDiscoveredReferrersTable() (err error) {
 	typeNameTitle := "Artifact Type"
 	typeNameLength := len(typeNameTitle)
 	for _, ref := range h.referrers {
@@ -78,13 +87,20 @@ func (h *discoverHandler) printDiscoveredReferrersTable() error {
 		}
 	}
 
-	print := func(key string, value interface{}) {
-		fmt.Fprintln(h.out, key, strings.Repeat(" ", typeNameLength-len(key)+1), value)
+	printKey := func(key string, value interface{}) (err error) {
+		_, err = fmt.Fprintln(h.out, key, strings.Repeat(" ", typeNameLength-len(key)+1), value)
+		return err
 	}
 
-	print(typeNameTitle, "Digest")
+	err = printKey(typeNameTitle, "Digest")
+	if err != nil {
+		return err
+	}
 	for _, ref := range h.referrers {
-		print(ref.ArtifactType, ref.Digest)
+		err = printKey(ref.ArtifactType, ref.Digest)
+		if err != nil {
+			return err
+		}
 		if h.verbose {
 			if err := output.PrintPrettyJSON(h.out, ref); err != nil {
 				return fmt.Errorf("error printing JSON: %w", err)

cmd/oras/internal/display/metadata/table/discover_test.go

@@ -20,6 +20,8 @@ import (
 	"testing"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+	"oras.land/oras/internal/testutils"
 )
 
 func TestTableDiscoverHandler_OneReferrer(t *testing.T) {
@@ -138,3 +140,36 @@ func TestTableDiscoverHandler_Failure(t *testing.T) {
 		t.Errorf("Expected error <%s> actual error <%s>", expected, err.Error())
 	}
 }
+
+func Test_discoverHandler_Render(t *testing.T) {
+	root := ocispec.Descriptor{Digest: "root"}
+	one := ocispec.Descriptor{ArtifactType: ocispec.MediaTypeImageLayer, Digest: "one"}
+	two := ocispec.Descriptor{ArtifactType: ocispec.MediaTypeImageLayer, Digest: "two"}
+
+	tests := []struct {
+		wf *testutils.WriteFailure
+	}{
+		{wf: testutils.NewWriteFailure(1)},
+		{wf: testutils.NewWriteFailure(2)},
+		{wf: testutils.NewWriteFailure(3)},
+		{wf: testutils.NewWriteFailure(4)},
+		{wf: testutils.NewWriteFailure(5)},
+	}
+	for _, tt := range tests {
+		t.Run(tt.wf.Expected(), func(t *testing.T) {
+			tdh := &discoverHandler{
+				out:          tt.wf,
+				rawReference: "rawRef",
+				root:         root,
+				verbose:      true,
+				referrers:    []ocispec.Descriptor{one, two},
+			}
+			err := tdh.Render()
+			if err == nil {
+				t.Errorf("OnDiscovered() Expected error <%s>", tt.wf.Expected())
+			} else if err.Error() != tt.wf.Expected() {
+				t.Errorf("Expected error <%s> actual error <%s>", tt.wf.Expected(), err.Error())
+			}
+		})
+	}
+}

internal/testutils/writer_failure.go

@@ -0,0 +1,42 @@
+/*
+Copyright The ORAS Authors.
+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
+
+http://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 testutils
+
+import "fmt"
+
+type WriteFailure struct {
+	count int
+	err   error
+}
+
+func NewWriteFailure(count int) *WriteFailure {
+	return &WriteFailure{
+		count: count,
+		err:   fmt.Errorf("failed on %d", count),
+	}
+}
+
+func (wf *WriteFailure) Write(p []byte) (n int, err error) {
+	wf.count = wf.count - 1
+	if wf.count <= 0 {
+		return 0, wf.err
+	}
+	return len(p), nil
+}
+
+func (wf *WriteFailure) Expected() string {
+	return wf.err.Error()
+}