linter: enable nilerr

A number of cases looked suspicious, so I marked them with `FIXME`s to
leave some breadcrumbs.

Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

13 files changed, 34 insertions, 22 deletions

diff --git a/pkg/api/handlers/utils/images.go b/pkg/api/handlers/utils/images.go
index 15b16bc43..7154f5616 100644
--- a/pkg/api/handlers/utils/images.go
+++ b/pkg/api/handlers/utils/images.go
@@ -63,7 +63,7 @@ func IsRegistryReference(name string) error {
 	imageRef, err := alltransports.ParseImageName(name)
 	if err != nil {
 		// No supported transport -> assume a docker-stype reference.
-		return nil
+		return nil // nolint: nilerr
 	}
 	if imageRef.Transport().Name() == docker.Transport.Name() {
 		return nil
diff --git a/pkg/bindings/containers/attach.go b/pkg/bindings/containers/attach.go
index f410606e4..0c6ebdd2f 100644
--- a/pkg/bindings/containers/attach.go
+++ b/pkg/bindings/containers/attach.go
@@ -279,7 +279,7 @@ func DemuxFrame(r io.Reader, buffer []byte, length int) (frame []byte, err error
 
 	n, err := io.ReadFull(r, buffer[0:length])
 	if err != nil {
-		return nil, nil
+		return nil, err
 	}
 	if n < length {
 		err = io.ErrUnexpectedEOF
diff --git a/pkg/bindings/test/common_test.go b/pkg/bindings/test/common_test.go
index f51e5f404..f2602967b 100644
--- a/pkg/bindings/test/common_test.go
+++ b/pkg/bindings/test/common_test.go
@@ -211,7 +211,7 @@ func (b *bindingTest) RunTopContainer(containerName *string, podName *string) (s
 	}
 	ctr, err := containers.CreateWithSpec(b.conn, s, nil)
 	if err != nil {
-		return "", nil
+		return "", err
 	}
 	err = containers.Start(b.conn, ctr.ID, nil)
 	if err != nil {
diff --git a/pkg/checkpoint/crutils/checkpoint_restore_utils.go b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
index 2765d18e8..5b2097a71 100644
--- a/pkg/checkpoint/crutils/checkpoint_restore_utils.go
+++ b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
@@ -99,13 +99,12 @@ func CRRemoveDeletedFiles(id, baseDirectory, containerRootDirectory string) erro
 // root file system changes on top of containerRootDirectory
 func CRApplyRootFsDiffTar(baseDirectory, containerRootDirectory string) error {
 	rootfsDiffPath := filepath.Join(baseDirectory, metadata.RootFsDiffTar)
-	if _, err := os.Stat(rootfsDiffPath); err != nil {
-		// Only do this if a rootfs-diff.tar actually exists
-		return nil
-	}
-
+	// Only do this if a rootfs-diff.tar actually exists
 	rootfsDiffFile, err := os.Open(rootfsDiffPath)
 	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
 		return errors.Wrap(err, "failed to open root file-system diff file")
 	}
 	defer rootfsDiffFile.Close()
diff --git a/pkg/domain/filters/containers.go b/pkg/domain/filters/containers.go
index 85ba4f84f..e30013647 100644
--- a/pkg/domain/filters/containers.go
+++ b/pkg/domain/filters/containers.go
@@ -213,8 +213,10 @@ func GenerateContainerFilterFuncs(filter string, filterValues []string, r *libpo
 		for _, val := range filterValues {
 			net, err := r.Network().NetworkInspect(val)
 			if err != nil {
-				// ignore not found errors
-				break
+				if errors.Cause(err) == define.ErrNoSuchNetwork {
+					continue
+				}
+				return nil, err
 			}
 			inputNetNames = append(inputNetNames, net.Name)
 		}
diff --git a/pkg/domain/filters/pods.go b/pkg/domain/filters/pods.go
index 2f9442dff..8eea8968d 100644
--- a/pkg/domain/filters/pods.go
+++ b/pkg/domain/filters/pods.go
@@ -131,8 +131,10 @@ func GeneratePodFilterFunc(filter string, filterValues []string, r *libpod.Runti
 		for _, val := range filterValues {
 			net, err := r.Network().NetworkInspect(val)
 			if err != nil {
-				// ignore not found errors
-				break
+				if errors.Cause(err) == define.ErrNoSuchNetwork {
+					continue
+				}
+				return nil, err
 			}
 			inputNetNames = append(inputNetNames, net.Name)
 		}
diff --git a/pkg/domain/infra/abi/volumes.go b/pkg/domain/infra/abi/volumes.go
index 19fc6d2d3..f59f11e20 100644
--- a/pkg/domain/infra/abi/volumes.go
+++ b/pkg/domain/infra/abi/volumes.go
@@ -171,7 +171,8 @@ func (ic *ContainerEngine) VolumeMounted(ctx context.Context, nameOrID string) (
 	}
 	mountCount, err := vol.MountCount()
 	if err != nil {
-		return &entities.BoolReport{Value: false}, nil
+		// FIXME: this error should probably be returned
+		return &entities.BoolReport{Value: false}, nil // nolint: nilerr
 	}
 	if mountCount > 0 {
 		return &entities.BoolReport{Value: true}, nil
diff --git a/pkg/domain/infra/tunnel/containers.go b/pkg/domain/infra/tunnel/containers.go
index 046c2509d..8a65a22bf 100644
--- a/pkg/domain/infra/tunnel/containers.go
+++ b/pkg/domain/infra/tunnel/containers.go
@@ -840,7 +840,7 @@ func (ic *ContainerEngine) ContainerRun(ctx context.Context, opts entities.Conta
 	if eventsErr != nil || lastEvent == nil {
 		logrus.Errorf("Cannot get exit code: %v", err)
 		report.ExitCode = define.ExecErrorCodeNotFound
-		return &report, nil // compat with local client
+		return &report, nil // nolint: nilerr
 	}
 
 	report.ExitCode = lastEvent.ContainerExitCode
diff --git a/pkg/errorhandling/errorhandling.go b/pkg/errorhandling/errorhandling.go
index 04110b62a..e33c26032 100644
--- a/pkg/errorhandling/errorhandling.go
+++ b/pkg/errorhandling/errorhandling.go
@@ -28,7 +28,7 @@ func JoinErrors(errs []error) error {
 
 	finalErr := multiE.ErrorOrNil()
 	if finalErr == nil {
-		return finalErr
+		return nil
 	}
 	return errors.New(strings.TrimSpace(finalErr.Error()))
 }
diff --git a/pkg/machine/fedora.go b/pkg/machine/fedora.go
index b26921b52..bcf694def 100644
--- a/pkg/machine/fedora.go
+++ b/pkg/machine/fedora.go
@@ -59,7 +59,10 @@ func (f FedoraDownload) Get() *Download {
 func (f FedoraDownload) HasUsableCache() (bool, error) {
 	info, err := os.Stat(f.LocalPath)
 	if err != nil {
-		return false, nil
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, err
 	}
 	return info.Size() == f.Size, nil
 }
diff --git a/pkg/machine/qemu/machine.go b/pkg/machine/qemu/machine.go
index 46f838f8b..ddb49124d 100644
--- a/pkg/machine/qemu/machine.go
+++ b/pkg/machine/qemu/machine.go
@@ -626,7 +626,8 @@ func (v *MachineVM) Stop(name string, _ machine.StopOptions) error {
 	}
 
 	if err := qmpMonitor.Disconnect(); err != nil {
-		return nil
+		// FIXME: this error should probably be returned
+		return nil // nolint: nilerr
 	}
 
 	disconnected = true
@@ -755,7 +756,8 @@ func (v *MachineVM) isRunning() (bool, error) {
 	// Check if we can dial it
 	monitor, err := qmp.NewSocketMonitor(v.QMPMonitor.Network, v.QMPMonitor.Address, v.QMPMonitor.Timeout)
 	if err != nil {
-		return false, nil
+		// FIXME: this error should probably be returned
+		return false, nil // nolint: nilerr
 	}
 	if err := monitor.Connect(); err != nil {
 		return false, err
diff --git a/pkg/rootless/rootless.go b/pkg/rootless/rootless.go
index 93b4e2e9f..f526aa9e1 100644
--- a/pkg/rootless/rootless.go
+++ b/pkg/rootless/rootless.go
@@ -16,12 +16,15 @@ import (
 // file.
 func TryJoinPauseProcess(pausePidPath string) (bool, int, error) {
 	if _, err := os.Stat(pausePidPath); err != nil {
-		return false, -1, nil
+		if os.IsNotExist(err) {
+			return false, -1, nil
+		}
+		return false, -1, err
 	}
 
 	became, ret, err := TryJoinFromFilePaths("", false, []string{pausePidPath})
 	if err == nil {
-		return became, ret, err
+		return became, ret, nil
 	}
 
 	// It could not join the pause process, let's lock the file before trying to delete it.
@@ -46,7 +49,7 @@ func TryJoinPauseProcess(pausePidPath string) (bool, int, error) {
 	if err != nil {
 		// It is still failing.  We can safely remove it.
 		os.Remove(pausePidPath)
-		return false, -1, nil
+		return false, -1, nil // nolint: nilerr
 	}
 	return became, ret, err
 }
diff --git a/pkg/util/utils.go b/pkg/util/utils.go
index 925ff9830..1beb3b28e 100644
--- a/pkg/util/utils.go
+++ b/pkg/util/utils.go
@@ -727,7 +727,7 @@ func SocketPath() (string, error) {
 func LookupUser(name string) (*user.User, error) {
 	// Assume UID look up first, if it fails lookup by username
 	if u, err := user.LookupId(name); err == nil {
-		return u, err
+		return u, nil
 	}
 	return user.Lookup(name)
 }