cli/command/context: context ls: always show current context

if a context is set (e.g. through DOCKER_CONTEXT or the CLI config file), but
wasn't found, then a "stub" context is added, including an error message that
the context doesn't exist.

    DOCKER_CONTEXT=nosuchcontext docker context ls
    NAME              DESCRIPTION                               DOCKER ENDPOINT               ERROR
    default           Current DOCKER_HOST based configuration   unix:///var/run/docker.sock
    nosuchcontext *                                                                           context "nosuchcontext": context not found: …

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/context/list.go

@@ -50,10 +50,14 @@ func runList(dockerCli command.Cli, opts *listOptions) error {
 	}
 	var (
 		curContext = dockerCli.CurrentContext()
+		curFound   bool
 		contexts   []*formatter.ClientContext
 	)
 	for _, rawMeta := range contextMap {
 		isCurrent := rawMeta.Name == curContext
+		if isCurrent {
+			curFound = true
+		}
 		meta, err := command.GetDockerContext(rawMeta)
 		if err != nil {
 			// Add a stub-entry to the list, including the error-message
@@ -79,6 +83,21 @@ func runList(dockerCli command.Cli, opts *listOptions) error {
 		}
 		contexts = append(contexts, &desc)
 	}
+	if !curFound {
+		// The currently specified context wasn't found. We add a stub-entry
+		// to the list, including the error-message indicating that the context
+		// wasn't found.
+		var errMsg string
+		_, err := dockerCli.ContextStore().GetMetadata(curContext)
+		if err != nil {
+			errMsg = err.Error()
+		}
+		contexts = append(contexts, &formatter.ClientContext{
+			Name:    curContext,
+			Current: true,
+			Error:   errMsg,
+		})
+	}
 	sort.Slice(contexts, func(i, j int) bool {
 		return sortorder.NaturalLess(contexts[i].Name, contexts[j].Name)
 	})

cli/command/context/list_test.go

@@ -39,3 +39,11 @@ func TestListQuiet(t *testing.T) {
 	assert.NilError(t, runList(cli, &listOptions{quiet: true}))
 	golden.Assert(t, cli.OutBuffer().String(), "quiet-list.golden")
 }
+
+func TestListError(t *testing.T) {
+	cli := makeFakeCli(t)
+	cli.SetCurrentContext("nosuchcontext")
+	cli.OutBuffer().Reset()
+	assert.NilError(t, runList(cli, &listOptions{}))
+	golden.Assert(t, cli.OutBuffer().String(), "list-with-error.golden")
+}

cli/command/context/testdata/list-with-error.golden

@@ -0,0 +1,3 @@
+NAME              DESCRIPTION                               DOCKER ENDPOINT               ERROR
+default           Current DOCKER_HOST based configuration   unix:///var/run/docker.sock   
+nosuchcontext *                                                                           context "nosuchcontext": context not found: …

cli/command/context/testdata/list.golden

@@ -1,5 +1,5 @@
-NAME        DESCRIPTION                               DOCKER ENDPOINT
-current *   description of current                    https://someswarmserver.example.com
-default     Current DOCKER_HOST based configuration   unix:///var/run/docker.sock
-other       description of other                      https://someswarmserver.example.com
-unset       description of unset                      https://someswarmserver.example.com
+NAME        DESCRIPTION                               DOCKER ENDPOINT                       ERROR
+current *   description of current                    https://someswarmserver.example.com   
+default     Current DOCKER_HOST based configuration   unix:///var/run/docker.sock           
+other       description of other                      https://someswarmserver.example.com   
+unset       description of unset                      https://someswarmserver.example.com   

cli/command/formatter/context.go

@@ -6,6 +6,8 @@ const (
 
 	dockerEndpointHeader = "DOCKER ENDPOINT"
 	quietContextFormat   = "{{.Name}}"
+
+	maxErrLength = 45
 )
 
 // NewClientContextFormat returns a Format for rendering using a Context
@@ -80,7 +82,7 @@ func (c *clientContextContext) DockerEndpoint() string {
 // Error returns the truncated error (if any) that occurred when loading the context.
 func (c *clientContextContext) Error() string {
 	// TODO(thaJeztah) add "--no-trunc" option to context ls and set default to 30 cols to match "docker service ps"
-	return Ellipsis(c.c.Error, 45)
+	return Ellipsis(c.c.Error, maxErrLength)
 }
 
 // KubernetesEndpoint returns the kubernetes endpoint.

cli/context/store/metadatastore.go

@@ -59,7 +59,7 @@ func parseTypedOrMap(payload []byte, getter TypeGetter) (interface{}, error) {
 func (s *metadataStore) get(name string) (Metadata, error) {
 	m, err := s.getByID(contextdirOf(name))
 	if err != nil {
-		return m, errors.Wrapf(err, "load context %q", name)
+		return m, errors.Wrapf(err, "context %q", name)
 	}
 	return m, nil
 }
@@ -68,7 +68,7 @@ func (s *metadataStore) getByID(id contextdir) (Metadata, error) {
 	bytes, err := os.ReadFile(filepath.Join(s.contextDir(id), metaFile))
 	if err != nil {
 		if errors.Is(err, os.ErrNotExist) {
-			return Metadata{}, errdefs.NotFound(errors.Wrap(err, "context does not exist"))
+			return Metadata{}, errdefs.NotFound(errors.Wrap(err, "context not found"))
 		}
 		return Metadata{}, err
 	}