Add completion for `--pid`

Signed-off-by: Harald Albers <github@albersweb.de>

cli/command/container/completion.go

@@ -64,6 +64,7 @@ func addCompletions(cmd *cobra.Command, dockerCLI completion.APIClientProvider)
 	_ = cmd.RegisterFlagCompletionFunc("ipc", completeIpc(dockerCLI))
 	_ = cmd.RegisterFlagCompletionFunc("link", completeLink(dockerCLI))
 	_ = cmd.RegisterFlagCompletionFunc("network", completion.NetworkNames(dockerCLI))
+	_ = cmd.RegisterFlagCompletionFunc("pid", completePid(dockerCLI))
 	_ = cmd.RegisterFlagCompletionFunc("platform", completion.Platforms)
 	_ = cmd.RegisterFlagCompletionFunc("pull", completion.FromList(PullImageAlways, PullImageMissing, PullImageNever))
 	_ = cmd.RegisterFlagCompletionFunc("restart", completeRestartPolicies)
@@ -99,6 +100,20 @@ func completeLink(dockerCLI completion.APIClientProvider) func(cmd *cobra.Comman
 	}
 }
 
+// completePid implements shell completion for the `--pid` option  of `run` and `create`.
+func completePid(dockerCLI completion.APIClientProvider) func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		if len(toComplete) > 0 && strings.HasPrefix("container", toComplete) { //nolint:gocritic // not swapped, matches partly typed "container"
+			return []string{"container:"}, cobra.ShellCompDirectiveNoSpace
+		}
+		if strings.HasPrefix(toComplete, "container:") {
+			names, _ := completion.ContainerNames(dockerCLI, true)(cmd, args, toComplete)
+			return prefixWith("container:", names), cobra.ShellCompDirectiveNoFileComp
+		}
+		return []string{"container:", "host"}, cobra.ShellCompDirectiveNoFileComp
+	}
+}
+
 // containerNames contacts the API to get names and optionally IDs of containers.
 // In case of an error, an empty list is returned.
 func containerNames(dockerCLI completion.APIClientProvider, cmd *cobra.Command, args []string, toComplete string) []string {

cli/command/container/completion_test.go

@@ -4,6 +4,9 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/docker/cli/internal/test"
+	"github.com/docker/cli/internal/test/builders"
+	"github.com/docker/docker/api/types/container"
 	"github.com/moby/sys/signal"
 	"github.com/spf13/cobra"
 	"gotest.tools/v3/assert"
@@ -21,6 +24,48 @@ func TestCompleteLinuxCapabilityNames(t *testing.T) {
 	}
 }
 
+func TestCompletePid(t *testing.T) {
+	tests := []struct {
+		containerListFunc   func(container.ListOptions) ([]container.Summary, error)
+		toComplete          string
+		expectedCompletions []string
+		expectedDirective   cobra.ShellCompDirective
+	}{
+		{
+			toComplete:          "",
+			expectedCompletions: []string{"container:", "host"},
+			expectedDirective:   cobra.ShellCompDirectiveNoFileComp,
+		},
+		{
+			toComplete:          "c",
+			expectedCompletions: []string{"container:"},
+			expectedDirective:   cobra.ShellCompDirectiveNoSpace,
+		},
+		{
+			containerListFunc: func(container.ListOptions) ([]container.Summary, error) {
+				return []container.Summary{
+					*builders.Container("c1"),
+					*builders.Container("c2"),
+				}, nil
+			},
+			toComplete:          "container:",
+			expectedCompletions: []string{"container:c1", "container:c2"},
+			expectedDirective:   cobra.ShellCompDirectiveNoFileComp,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.toComplete, func(t *testing.T) {
+			cli := test.NewFakeCli(&fakeClient{
+				containerListFunc: tc.containerListFunc,
+			})
+			completions, directive := completePid(cli)(NewRunCommand(cli), nil, tc.toComplete)
+			assert.Check(t, is.DeepEqual(completions, tc.expectedCompletions))
+			assert.Check(t, is.Equal(directive, tc.expectedDirective))
+		})
+	}
+}
+
 func TestCompleteRestartPolicies(t *testing.T) {
 	values, directives := completeRestartPolicies(nil, nil, "")
 	assert.Check(t, is.Equal(directives&cobra.ShellCompDirectiveNoFileComp, cobra.ShellCompDirectiveNoFileComp), "Should not perform file completion")