cli: shell completion via cobra + dynamic resource name lookups

Re-enable cobra's default `completion` subcommand (`banger completion
bash|zsh|fish|powershell`). Plus live resource-name suggestions that
hit the running daemon via the same RPC the real commands use:

  vm start/stop/restart/delete/kill/set         → completeVMNames (variadic)
  vm ssh/show/logs/stats/ports/...              → completeVMNameOnlyAtPos0
  vm session list/start                         → completeVMNameOnlyAtPos0
  vm session show/logs/stop/kill/attach/send    → completeSessionNames (vm + session)
  image show/delete/promote                     → completeImageNameOnlyAtPos0
  kernel show/rm                                → completeKernelNameOnlyAtPos0
  vm run/create --image, image pull/register --kernel-ref → flag-value completion

Design notes in internal/cli/completion.go: completers never auto-start
the daemon (ping-check, bail with NoFileComp on miss), so tab-completion
stays a zero-cost probe. Variadic completers exclude already-entered
args to avoid duplicate suggestions.

README: install recipes for bash / zsh / fish.
This commit is contained in:
Thales Maciel 2026-04-19 12:12:40 -03:00
parent 346eaba673
commit e3eaa0c797
No known key found for this signature in database
GPG key ID: 33112E6833C34679
4 changed files with 556 additions and 76 deletions

202
internal/cli/completion.go Normal file
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@ -0,0 +1,202 @@
package cli
import (
"context"
"banger/internal/api"
"banger/internal/paths"
"banger/internal/rpc"
"github.com/spf13/cobra"
)
// Completion helpers. Design notes:
//
// - Never auto-start the daemon. If it isn't running, return no
// suggestions + NoFileComp so the shell doesn't fall back to file
// completion (there are no local files that would plausibly match a
// VM or image name).
// - Filter out names already in args — avoids suggesting the same VM
// twice on variadic commands like `vm stop a b <tab>`.
// - Fail silently. Completion is advisory; any error path returns an
// empty suggestion list rather than propagating to the user.
// completionListerFunc is the seam used by tests to avoid touching a
// real daemon socket.
var completionListerFunc = func(ctx context.Context, socketPath, method string) ([]string, error) {
switch method {
case "vm.list":
result, err := rpc.Call[api.VMListResult](ctx, socketPath, method, api.Empty{})
if err != nil {
return nil, err
}
names := make([]string, 0, len(result.VMs))
for _, vm := range result.VMs {
if vm.Name != "" {
names = append(names, vm.Name)
}
}
return names, nil
case "image.list":
result, err := rpc.Call[api.ImageListResult](ctx, socketPath, method, api.Empty{})
if err != nil {
return nil, err
}
names := make([]string, 0, len(result.Images))
for _, image := range result.Images {
if image.Name != "" {
names = append(names, image.Name)
}
}
return names, nil
case "kernel.list":
result, err := rpc.Call[api.KernelListResult](ctx, socketPath, method, api.Empty{})
if err != nil {
return nil, err
}
names := make([]string, 0, len(result.Entries))
for _, entry := range result.Entries {
if entry.Name != "" {
names = append(names, entry.Name)
}
}
return names, nil
}
return nil, nil
}
// completionSessionListerFunc is the seam for guest-session name lookups
// scoped to a VM.
var completionSessionListerFunc = func(ctx context.Context, socketPath, vmIDOrName string) ([]string, error) {
result, err := rpc.Call[api.GuestSessionListResult](ctx, socketPath, "guest.session.list", api.VMRefParams{IDOrName: vmIDOrName})
if err != nil {
return nil, err
}
names := make([]string, 0, len(result.Sessions))
for _, session := range result.Sessions {
if session.Name != "" {
names = append(names, session.Name)
}
}
return names, nil
}
// daemonSocketForCompletion returns the socket path IFF the daemon is
// already running. Returns "", false when no daemon is up — completion
// callers use this as the bail signal.
func daemonSocketForCompletion(ctx context.Context) (string, bool) {
layout, err := paths.Resolve()
if err != nil {
return "", false
}
if _, err := daemonPingFunc(ctx, layout.SocketPath); err != nil {
return "", false
}
return layout.SocketPath, true
}
// filterPrefix returns the subset of candidates starting with toComplete
// that aren't in exclude. Comparison is case-sensitive because VM/image
// names preserve case.
func filterPrefix(candidates, exclude []string, toComplete string) []string {
excludeSet := make(map[string]struct{}, len(exclude))
for _, e := range exclude {
excludeSet[e] = struct{}{}
}
out := make([]string, 0, len(candidates))
for _, c := range candidates {
if _, skip := excludeSet[c]; skip {
continue
}
if toComplete == "" || hasPrefix(c, toComplete) {
out = append(out, c)
}
}
return out
}
func hasPrefix(s, prefix string) bool {
return len(s) >= len(prefix) && s[:len(prefix)] == prefix
}
func completeVMNames(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
socket, ok := daemonSocketForCompletion(cmd.Context())
if !ok {
return nil, cobra.ShellCompDirectiveNoFileComp
}
names, err := completionListerFunc(cmd.Context(), socket, "vm.list")
if err != nil {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return filterPrefix(names, args, toComplete), cobra.ShellCompDirectiveNoFileComp
}
// completeVMNameOnlyAtPos0 restricts VM-name completion to the first
// positional argument. Used by commands like `vm ssh <vm> [ssh args...]`
// where args after pos 0 are free-form.
func completeVMNameOnlyAtPos0(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
if len(args) > 0 {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return completeVMNames(cmd, args, toComplete)
}
func completeImageNameOnlyAtPos0(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
if len(args) > 0 {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return completeImageNames(cmd, args, toComplete)
}
func completeKernelNameOnlyAtPos0(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
if len(args) > 0 {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return completeKernelNames(cmd, args, toComplete)
}
func completeImageNames(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
socket, ok := daemonSocketForCompletion(cmd.Context())
if !ok {
return nil, cobra.ShellCompDirectiveNoFileComp
}
names, err := completionListerFunc(cmd.Context(), socket, "image.list")
if err != nil {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return filterPrefix(names, args, toComplete), cobra.ShellCompDirectiveNoFileComp
}
func completeKernelNames(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
socket, ok := daemonSocketForCompletion(cmd.Context())
if !ok {
return nil, cobra.ShellCompDirectiveNoFileComp
}
names, err := completionListerFunc(cmd.Context(), socket, "kernel.list")
if err != nil {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return filterPrefix(names, args, toComplete), cobra.ShellCompDirectiveNoFileComp
}
// completeSessionNames handles `... <vm> <session>` commands: pos 0
// completes VMs, pos 1 completes sessions owned by args[0], pos 2+ is
// silent.
func completeSessionNames(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
switch len(args) {
case 0:
return completeVMNames(cmd, args, toComplete)
case 1:
socket, ok := daemonSocketForCompletion(cmd.Context())
if !ok {
return nil, cobra.ShellCompDirectiveNoFileComp
}
names, err := completionSessionListerFunc(cmd.Context(), socket, args[0])
if err != nil {
return nil, cobra.ShellCompDirectiveNoFileComp
}
return filterPrefix(names, nil, toComplete), cobra.ShellCompDirectiveNoFileComp
default:
return nil, cobra.ShellCompDirectiveNoFileComp
}
}