Add shell completion with cobra

Allow automatic generation for shell completion scripts
with the internal cobra functions (requires v1.0.0+).

This should replace the handwritten completion scripts
and even adds support for fish. With this approach it is
less likley that completions and code are out of sync.

We can now create the scripts with
- podman completion bash
- podman completion zsh
- podman completion fish

To test the completion run:
source <(podman completion bash)

The same works for podman-remote and podman --remote and
it will complete your remote containers/images with
the correct endpoints values from --url/--connection.

The completion logic is written in go and provided by the
cobra library. The completion functions lives in
`cmd/podman/completion/completion.go`.

The unit test at cmd/podman/shell_completion_test.go checks
if each command and flag has an autocompletion function set.
This prevents that commands and flags have no shell completion set.

This commit does not replace the current autocompletion scripts.

Closes #6440

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

1 files changed, 112 insertions, 27 deletions

diff --git a/cmd/podman/root.go b/cmd/podman/root.go
index b59b8341a..0a44f5eac 100644
--- a/cmd/podman/root.go
+++ b/cmd/podman/root.go
@@ -8,7 +8,9 @@ import (
 	"runtime/pprof"
 	"strings"
 
+	"github.com/containers/common/pkg/completion"
 	"github.com/containers/common/pkg/config"
+	"github.com/containers/podman/v2/cmd/podman/common"
 	"github.com/containers/podman/v2/cmd/podman/registry"
 	"github.com/containers/podman/v2/cmd/podman/validate"
 	"github.com/containers/podman/v2/libpod/define"
@@ -21,6 +23,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 )
 
 // HelpTemplate is the help template for podman commands
@@ -67,9 +70,10 @@ var (
 		Version:               version.Version.String(),
 		DisableFlagsInUseLine: true,
 	}
-	logLevels = []string{"debug", "info", "warn", "error", "fatal", "panic"}
-	logLevel  = "error"
-	useSyslog bool
+
+	logLevel       = "error"
+	useSyslog      bool
+	requireCleanup = true
 )
 
 func init() {
@@ -102,11 +106,36 @@ func persistentPreRunE(cmd *cobra.Command, args []string) error {
 	// TODO: Remove trace statement in podman V2.1
 	logrus.Debugf("Called %s.PersistentPreRunE(%s)", cmd.Name(), strings.Join(os.Args, " "))
 
-	// Help and commands with subcommands are special cases, no need for more setup
-	if cmd.Name() == "help" || cmd.HasSubCommands() {
+	// Help, completion and commands with subcommands are special cases, no need for more setup
+	// Completion cmd is used to generate the shell scripts
+	if cmd.Name() == "help" || cmd.Name() == "completion" || cmd.HasSubCommands() {
+		requireCleanup = false
 		return nil
 	}
 
+	// Special case if command is hidden completion command ("__complete","__completeNoDesc")
+	// Since __completeNoDesc is an alias the cm.Name is always __complete
+	if cmd.Name() == cobra.ShellCompRequestCmd {
+		// Parse the cli arguments after the the completion cmd (always called as second argument)
+		// This ensures that the --url, --identity and --connection flags are properly set
+		compCmd, _, err := cmd.Root().Traverse(os.Args[2:])
+		if err != nil {
+			return err
+		}
+		// If we don't complete the root cmd hide all root flags
+		// so they won't show up in the completions on subcommands.
+		if compCmd != compCmd.Root() {
+			compCmd.Root().Flags().VisitAll(func(flag *pflag.Flag) {
+				flag.Hidden = true
+			})
+		}
+		// No need for further setup when completing commands with subcommands.
+		if compCmd.HasSubCommands() {
+			requireCleanup = false
+			return nil
+		}
+	}
+
 	cfg := registry.PodmanConfig()
 
 	// --connection is not as "special" as --remote so we can wait and process it here
@@ -203,8 +232,7 @@ func persistentPostRunE(cmd *cobra.Command, args []string) error {
 	// TODO: Remove trace statement in podman V2.1
 	logrus.Debugf("Called %s.PersistentPostRunE(%s)", cmd.Name(), strings.Join(os.Args, " "))
 
-	// Help and commands with subcommands are special cases, no need for more cleanup
-	if cmd.Name() == "help" || cmd.HasSubCommands() {
+	if !requireCleanup {
 		return nil
 	}
 
@@ -226,14 +254,14 @@ func persistentPostRunE(cmd *cobra.Command, args []string) error {
 
 func loggingHook() {
 	var found bool
-	for _, l := range logLevels {
+	for _, l := range common.LogLevels {
 		if l == strings.ToLower(logLevel) {
 			found = true
 			break
 		}
 	}
 	if !found {
-		fmt.Fprintf(os.Stderr, "Log Level %q is not supported, choose from: %s\n", logLevel, strings.Join(logLevels, ", "))
+		fmt.Fprintf(os.Stderr, "Log Level %q is not supported, choose from: %s\n", logLevel, strings.Join(common.LogLevels, ", "))
 		os.Exit(1)
 	}
 
@@ -254,9 +282,18 @@ func rootFlags(cmd *cobra.Command, opts *entities.PodmanConfig) {
 	srv, uri, ident := resolveDestination()
 
 	lFlags := cmd.Flags()
-	lFlags.StringVarP(&opts.Engine.ActiveService, "connection", "c", srv, "Connection to use for remote Podman service")
-	lFlags.StringVar(&opts.URI, "url", uri, "URL to access Podman service (CONTAINER_HOST)")
-	lFlags.StringVar(&opts.Identity, "identity", ident, "path to SSH identity file, (CONTAINER_SSHKEY)")
+
+	connectionFlagName := "connection"
+	lFlags.StringVarP(&opts.Engine.ActiveService, connectionFlagName, "c", srv, "Connection to use for remote Podman service")
+	_ = cmd.RegisterFlagCompletionFunc(connectionFlagName, common.AutocompleteSystemConnections)
+
+	urlFlagName := "url"
+	lFlags.StringVar(&opts.URI, urlFlagName, uri, "URL to access Podman service (CONTAINER_HOST)")
+	_ = cmd.RegisterFlagCompletionFunc(urlFlagName, completion.AutocompleteDefault)
+
+	identityFlagName := "identity"
+	lFlags.StringVar(&opts.Identity, identityFlagName, ident, "path to SSH identity file, (CONTAINER_SSHKEY)")
+	_ = cmd.RegisterFlagCompletionFunc(identityFlagName, completion.AutocompleteDefault)
 
 	lFlags.BoolVarP(&opts.Remote, "remote", "r", false, "Access remote Podman service (default false)")
 	pFlags := cmd.PersistentFlags()
@@ -266,25 +303,67 @@ func rootFlags(cmd *cobra.Command, opts *entities.PodmanConfig) {
 		}
 		opts.Remote = true
 	} else {
-		pFlags.StringVar(&cfg.Engine.CgroupManager, "cgroup-manager", cfg.Engine.CgroupManager, "Cgroup manager to use (\"cgroupfs\"|\"systemd\")")
+		cgroupManagerFlagName := "cgroup-manager"
+		pFlags.StringVar(&cfg.Engine.CgroupManager, cgroupManagerFlagName, cfg.Engine.CgroupManager, "Cgroup manager to use (\"cgroupfs\"|\"systemd\")")
+		_ = cmd.RegisterFlagCompletionFunc(cgroupManagerFlagName, common.AutocompleteCgroupManager)
+
 		pFlags.StringVar(&opts.CPUProfile, "cpu-profile", "", "Path for the cpu profiling results")
-		pFlags.StringVar(&opts.ConmonPath, "conmon", "", "Path of the conmon binary")
-		pFlags.StringVar(&cfg.Engine.NetworkCmdPath, "network-cmd-path", cfg.Engine.NetworkCmdPath, "Path to the command for configuring the network")
-		pFlags.StringVar(&cfg.Network.NetworkConfigDir, "cni-config-dir", cfg.Network.NetworkConfigDir, "Path of the configuration directory for CNI networks")
+
+		conmonFlagName := "conmon"
+		pFlags.StringVar(&opts.ConmonPath, conmonFlagName, "", "Path of the conmon binary")
+		_ = cmd.RegisterFlagCompletionFunc(conmonFlagName, completion.AutocompleteDefault)
+
+		networkCmdPathFlagName := "network-cmd-path"
+		pFlags.StringVar(&cfg.Engine.NetworkCmdPath, networkCmdPathFlagName, cfg.Engine.NetworkCmdPath, "Path to the command for configuring the network")
+		_ = cmd.RegisterFlagCompletionFunc(networkCmdPathFlagName, completion.AutocompleteDefault)
+
+		cniConfigDirFlagName := "cni-config-dir"
+		pFlags.StringVar(&cfg.Network.NetworkConfigDir, cniConfigDirFlagName, cfg.Network.NetworkConfigDir, "Path of the configuration directory for CNI networks")
+		_ = cmd.RegisterFlagCompletionFunc(cniConfigDirFlagName, completion.AutocompleteDefault)
+
 		pFlags.StringVar(&cfg.Containers.DefaultMountsFile, "default-mounts-file", cfg.Containers.DefaultMountsFile, "Path to default mounts file")
-		pFlags.StringVar(&cfg.Engine.EventsLogger, "events-backend", cfg.Engine.EventsLogger, `Events backend to use ("file"|"journald"|"none")`)
-		pFlags.StringSliceVar(&cfg.Engine.HooksDir, "hooks-dir", cfg.Engine.HooksDir, "Set the OCI hooks directory path (may be set multiple times)")
+
+		eventsBackendFlagName := "events-backend"
+		pFlags.StringVar(&cfg.Engine.EventsLogger, eventsBackendFlagName, cfg.Engine.EventsLogger, `Events backend to use ("file"|"journald"|"none")`)
+		_ = cmd.RegisterFlagCompletionFunc(eventsBackendFlagName, common.AutocompleteEventBackend)
+
+		hooksDirFlagName := "hooks-dir"
+		pFlags.StringSliceVar(&cfg.Engine.HooksDir, hooksDirFlagName, cfg.Engine.HooksDir, "Set the OCI hooks directory path (may be set multiple times)")
+		_ = cmd.RegisterFlagCompletionFunc(hooksDirFlagName, completion.AutocompleteDefault)
+
 		pFlags.IntVar(&opts.MaxWorks, "max-workers", (runtime.NumCPU()*3)+1, "The maximum number of workers for parallel operations")
-		pFlags.StringVar(&cfg.Engine.Namespace, "namespace", cfg.Engine.Namespace, "Set the libpod namespace, used to create separate views of the containers and pods on the system")
-		pFlags.StringVar(&cfg.Engine.StaticDir, "root", "", "Path to the root directory in which data, including images, is stored")
+
+		namespaceFlagName := "namespace"
+		pFlags.StringVar(&cfg.Engine.Namespace, namespaceFlagName, cfg.Engine.Namespace, "Set the libpod namespace, used to create separate views of the containers and pods on the system")
+		_ = cmd.RegisterFlagCompletionFunc(namespaceFlagName, completion.AutocompleteNone)
+
+		rootFlagName := "root"
+		pFlags.StringVar(&cfg.Engine.StaticDir, rootFlagName, "", "Path to the root directory in which data, including images, is stored")
+		_ = cmd.RegisterFlagCompletionFunc(rootFlagName, completion.AutocompleteDefault)
+
 		pFlags.StringVar(&opts.RegistriesConf, "registries-conf", "", "Path to a registries.conf to use for image processing")
-		pFlags.StringVar(&opts.Runroot, "runroot", "", "Path to the 'run directory' where all state information is stored")
-		pFlags.StringVar(&opts.RuntimePath, "runtime", "", "Path to the OCI-compatible binary used to run containers, default is /usr/bin/runc")
+
+		runrootFlagName := "runroot"
+		pFlags.StringVar(&opts.Runroot, runrootFlagName, "", "Path to the 'run directory' where all state information is stored")
+		_ = cmd.RegisterFlagCompletionFunc(runrootFlagName, completion.AutocompleteDefault)
+
+		runtimeFlagName := "runtime"
+		pFlags.StringVar(&opts.RuntimePath, runtimeFlagName, "", "Path to the OCI-compatible binary used to run containers, default is /usr/bin/runc")
+		_ = cmd.RegisterFlagCompletionFunc(runtimeFlagName, completion.AutocompleteDefault)
+
 		// -s is deprecated due to conflict with -s on subcommands
-		pFlags.StringVar(&opts.StorageDriver, "storage-driver", "", "Select which storage driver is used to manage storage of images and containers (default is overlay)")
-		pFlags.StringArrayVar(&opts.StorageOpts, "storage-opt", []string{}, "Used to pass an option to the storage driver")
+		storageDriverFlagName := "storage-driver"
+		pFlags.StringVar(&opts.StorageDriver, storageDriverFlagName, "", "Select which storage driver is used to manage storage of images and containers (default is overlay)")
+		_ = cmd.RegisterFlagCompletionFunc(storageDriverFlagName, completion.AutocompleteNone) //TODO: what can we recommend here?
+
+		storageOptFlagName := "storage-opt"
+		pFlags.StringArrayVar(&opts.StorageOpts, storageOptFlagName, []string{}, "Used to pass an option to the storage driver")
+		_ = cmd.RegisterFlagCompletionFunc(storageOptFlagName, completion.AutocompleteNone)
+
+		tmpdirFlagName := "tmpdir"
+		pFlags.StringVar(&opts.Engine.TmpDir, tmpdirFlagName, "", "Path to the tmp directory for libpod state content.\n\nNote: use the environment variable 'TMPDIR' to change the temporary storage location for container images, '/var/tmp'.\n")
+		_ = cmd.RegisterFlagCompletionFunc(tmpdirFlagName, completion.AutocompleteDefault)
 
-		pFlags.StringVar(&opts.Engine.TmpDir, "tmpdir", "", "Path to the tmp directory for libpod state content.\n\nNote: use the environment variable 'TMPDIR' to change the temporary storage location for container images, '/var/tmp'.\n")
 		pFlags.BoolVar(&opts.Trace, "trace", false, "Enable opentracing output (default false)")
 
 		// Hide these flags for both ABI and Tunneling
@@ -303,11 +382,17 @@ func rootFlags(cmd *cobra.Command, opts *entities.PodmanConfig) {
 	// Override default --help information of `--help` global flag
 	var dummyHelp bool
 	pFlags.BoolVar(&dummyHelp, "help", false, "Help for podman")
-	pFlags.StringVar(&logLevel, "log-level", logLevel, fmt.Sprintf("Log messages above specified level (%s)", strings.Join(logLevels, ", ")))
+
+	logLevelFlagName := "log-level"
+	pFlags.StringVar(&logLevel, logLevelFlagName, logLevel, fmt.Sprintf("Log messages above specified level (%s)", strings.Join(common.LogLevels, ", ")))
+	_ = rootCmd.RegisterFlagCompletionFunc(logLevelFlagName, common.AutocompleteLogLevel)
 
 	// Only create these flags for ABI connections
 	if !registry.IsRemote() {
-		pFlags.StringArrayVar(&opts.RuntimeFlags, "runtime-flag", []string{}, "add global flags for the container runtime")
+		runtimeflagFlagName := "runtime-flag"
+		pFlags.StringArrayVar(&opts.RuntimeFlags, runtimeflagFlagName, []string{}, "add global flags for the container runtime")
+		_ = rootCmd.RegisterFlagCompletionFunc(runtimeflagFlagName, completion.AutocompleteNone)
+
 		pFlags.BoolVar(&useSyslog, "syslog", false, "Output logging information to syslog as well as the console (default false)")
 	}
 }