forked from mirror/cobra
384 lines
15 KiB
Markdown
384 lines
15 KiB
Markdown
# Generating Bash Completions For Your Own cobra.Command
|
|
|
|
If you are using the generator you can create a completion command by running
|
|
|
|
```bash
|
|
cobra add completion
|
|
```
|
|
|
|
Update the help text show how to install the bash_completion Linux show here [Kubectl docs show mac options](https://kubernetes.io/docs/tasks/tools/install-kubectl/#enabling-shell-autocompletion)
|
|
|
|
Writing the shell script to stdout allows the most flexible use.
|
|
|
|
```go
|
|
// completionCmd represents the completion command
|
|
var completionCmd = &cobra.Command{
|
|
Use: "completion",
|
|
Short: "Generates bash completion scripts",
|
|
Long: `To load completion run
|
|
|
|
. <(bitbucket completion)
|
|
|
|
To configure your bash shell to load completions for each session add to your bashrc
|
|
|
|
# ~/.bashrc or ~/.profile
|
|
. <(bitbucket completion)
|
|
`,
|
|
Run: func(cmd *cobra.Command, args []string) {
|
|
rootCmd.GenBashCompletion(os.Stdout);
|
|
},
|
|
}
|
|
```
|
|
|
|
**Note:** The cobra generator may include messages printed to stdout for example if the config file is loaded, this will break the auto complete script
|
|
|
|
|
|
## Example from kubectl
|
|
|
|
Generating bash completions from a cobra command is incredibly easy. An actual program which does so for the kubernetes kubectl binary is as follows:
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"io/ioutil"
|
|
"os"
|
|
|
|
"k8s.io/kubernetes/pkg/kubectl/cmd"
|
|
"k8s.io/kubernetes/pkg/kubectl/cmd/util"
|
|
)
|
|
|
|
func main() {
|
|
kubectl := cmd.NewKubectlCommand(util.NewFactory(nil), os.Stdin, ioutil.Discard, ioutil.Discard)
|
|
kubectl.GenBashCompletionFile("out.sh")
|
|
}
|
|
```
|
|
|
|
`out.sh` will get you completions of subcommands and flags. Copy it to `/etc/bash_completion.d/` as described [here](https://debian-administration.org/article/316/An_introduction_to_bash_completion_part_1) and reset your terminal to use autocompletion. If you make additional annotations to your code, you can get even more intelligent and flexible behavior.
|
|
|
|
## Have the completions code complete your 'nouns'
|
|
|
|
### Static completion of nouns
|
|
|
|
This method allows you to provide a pre-defined list of completion choices for your nouns using the `validArgs` field.
|
|
For example, if you want `kubectl get [tab][tab]` to show a list of valid "nouns" you have to set them. Simplified code from `kubectl get` looks like:
|
|
|
|
```go
|
|
validArgs []string = { "pod", "node", "service", "replicationcontroller" }
|
|
|
|
cmd := &cobra.Command{
|
|
Use: "get [(-o|--output=)json|yaml|template|...] (RESOURCE [NAME] | RESOURCE/NAME ...)",
|
|
Short: "Display one or many resources",
|
|
Long: get_long,
|
|
Example: get_example,
|
|
Run: func(cmd *cobra.Command, args []string) {
|
|
err := RunGet(f, out, cmd, args)
|
|
util.CheckErr(err)
|
|
},
|
|
ValidArgs: validArgs,
|
|
}
|
|
```
|
|
|
|
Notice we put the "ValidArgs" on the "get" subcommand. Doing so will give results like
|
|
|
|
```bash
|
|
# kubectl get [tab][tab]
|
|
node pod replicationcontroller service
|
|
```
|
|
|
|
### Plural form and shortcuts for nouns
|
|
|
|
If your nouns have a number of aliases, you can define them alongside `ValidArgs` using `ArgAliases`:
|
|
|
|
```go
|
|
argAliases []string = { "pods", "nodes", "services", "svc", "replicationcontrollers", "rc" }
|
|
|
|
cmd := &cobra.Command{
|
|
...
|
|
ValidArgs: validArgs,
|
|
ArgAliases: argAliases
|
|
}
|
|
```
|
|
|
|
The aliases are not shown to the user on tab completion, but they are accepted as valid nouns by
|
|
the completion algorithm if entered manually, e.g. in:
|
|
|
|
```bash
|
|
# kubectl get rc [tab][tab]
|
|
backend frontend database
|
|
```
|
|
|
|
Note that without declaring `rc` as an alias, the completion algorithm would show the list of nouns
|
|
in this example again instead of the replication controllers.
|
|
|
|
### Dynamic completion of nouns
|
|
|
|
In some cases it is not possible to provide a list of possible completions in advance. Instead, the list of completions must be determined at execution-time. Cobra provides two ways of defining such dynamic completion of nouns. Note that both these methods can be used along-side each other as long as they are not both used for the same command.
|
|
|
|
**Note**: *Custom Completions written in Go* will automatically work for other shell-completion scripts (e.g., Fish shell), while *Custom Completions written in Bash* will only work for Bash shell-completion. It is therefore recommended to use *Custom Completions written in Go*.
|
|
|
|
#### 1. Custom completions of nouns written in Go
|
|
|
|
In a similar fashion as for static completions, you can use the `ValidArgsFunction` field to provide a Go function that Cobra will execute when it needs the list of completion choices for the nouns of a command. Note that either `ValidArgs` or `ValidArgsFunction` can be used for a single cobra command, but not both.
|
|
Simplified code from `helm status` looks like:
|
|
|
|
```go
|
|
cmd := &cobra.Command{
|
|
Use: "status RELEASE_NAME",
|
|
Short: "Display the status of the named release",
|
|
Long: status_long,
|
|
RunE: func(cmd *cobra.Command, args []string) {
|
|
RunGet(args[0])
|
|
},
|
|
ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
|
|
if len(args) != 0 {
|
|
return nil, cobra.ShellCompDirectiveNoFileComp
|
|
}
|
|
return getReleasesFromCluster(toComplete), cobra.ShellCompDirectiveNoFileComp
|
|
},
|
|
}
|
|
```
|
|
Where `getReleasesFromCluster()` is a Go function that obtains the list of current Helm releases running on the Kubernetes cluster.
|
|
Notice we put the `ValidArgsFunction` on the `status` subcommand. Let's assume the Helm releases on the cluster are: `harbor`, `notary`, `rook` and `thanos` then this dynamic completion will give results like
|
|
|
|
```bash
|
|
# helm status [tab][tab]
|
|
harbor notary rook thanos
|
|
```
|
|
You may have noticed the use of `cobra.ShellCompDirective`. These directives are bit fields allowing to control some shell completion behaviors for your particular completion. You can combine them with the bit-or operator such as `cobra.ShellCompDirectiveNoSpace | cobra.ShellCompDirectiveNoFileComp`
|
|
```go
|
|
// Indicates an error occurred and completions should be ignored.
|
|
ShellCompDirectiveError
|
|
// Indicates that the shell should not add a space after the completion,
|
|
// even if there is a single completion provided.
|
|
ShellCompDirectiveNoSpace
|
|
// Indicates that the shell should not provide file completion even when
|
|
// no completion is provided.
|
|
// This currently does not work for zsh or bash < 4
|
|
ShellCompDirectiveNoFileComp
|
|
// Indicates that the shell will perform its default behavior after completions
|
|
// have been provided (this implies !ShellCompDirectiveNoSpace && !ShellCompDirectiveNoFileComp).
|
|
ShellCompDirectiveDefault
|
|
```
|
|
|
|
When using the `ValidArgsFunction`, Cobra will call your registered function after having parsed all flags and arguments provided in the command-line. You therefore don't need to do this parsing yourself. For example, when a user calls `helm status --namespace my-rook-ns [tab][tab]`, Cobra will call your registered `ValidArgsFunction` after having parsed the `--namespace` flag, as it would have done when calling the `RunE` function.
|
|
|
|
##### Debugging
|
|
|
|
Cobra achieves dynamic completions written in Go through the use of a hidden command called by the completion script. To debug your Go completion code, you can call this hidden command directly:
|
|
```bash
|
|
# helm __complete status har<ENTER>
|
|
harbor
|
|
:4
|
|
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr
|
|
```
|
|
***Important:*** If the noun to complete is empty, you must pass an empty parameter to the `__complete` command:
|
|
```bash
|
|
# helm __complete status ""<ENTER>
|
|
harbor
|
|
notary
|
|
rook
|
|
thanos
|
|
:4
|
|
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr
|
|
```
|
|
Calling the `__complete` command directly allows you to run the Go debugger to troubleshoot your code. You can also add printouts to your code; Cobra provides the following functions to use for printouts in Go completion code:
|
|
```go
|
|
// Prints to the completion script debug file (if BASH_COMP_DEBUG_FILE
|
|
// is set to a file path) and optionally prints to stderr.
|
|
cobra.CompDebug(msg string, printToStdErr bool) {
|
|
cobra.CompDebugln(msg string, printToStdErr bool)
|
|
|
|
// Prints to the completion script debug file (if BASH_COMP_DEBUG_FILE
|
|
// is set to a file path) and to stderr.
|
|
cobra.CompError(msg string)
|
|
cobra.CompErrorln(msg string)
|
|
```
|
|
***Important:*** You should **not** leave traces that print to stdout in your completion code as they will be interpreted as completion choices by the completion script. Instead, use the cobra-provided debugging traces functions mentioned above.
|
|
|
|
#### 2. Custom completions of nouns written in Bash
|
|
|
|
This method allows you to inject bash functions into the completion script. Those bash functions are responsible for providing the completion choices for your own completions.
|
|
|
|
Some more actual code that works in kubernetes:
|
|
|
|
```bash
|
|
const (
|
|
bash_completion_func = `__kubectl_parse_get()
|
|
{
|
|
local kubectl_output out
|
|
if kubectl_output=$(kubectl get --no-headers "$1" 2>/dev/null); then
|
|
out=($(echo "${kubectl_output}" | awk '{print $1}'))
|
|
COMPREPLY=( $( compgen -W "${out[*]}" -- "$cur" ) )
|
|
fi
|
|
}
|
|
|
|
__kubectl_get_resource()
|
|
{
|
|
if [[ ${#nouns[@]} -eq 0 ]]; then
|
|
return 1
|
|
fi
|
|
__kubectl_parse_get ${nouns[${#nouns[@]} -1]}
|
|
if [[ $? -eq 0 ]]; then
|
|
return 0
|
|
fi
|
|
}
|
|
|
|
__kubectl_custom_func() {
|
|
case ${last_command} in
|
|
kubectl_get | kubectl_describe | kubectl_delete | kubectl_stop)
|
|
__kubectl_get_resource
|
|
return
|
|
;;
|
|
*)
|
|
;;
|
|
esac
|
|
}
|
|
`)
|
|
```
|
|
|
|
And then I set that in my command definition:
|
|
|
|
```go
|
|
cmds := &cobra.Command{
|
|
Use: "kubectl",
|
|
Short: "kubectl controls the Kubernetes cluster manager",
|
|
Long: `kubectl controls the Kubernetes cluster manager.
|
|
|
|
Find more information at https://github.com/GoogleCloudPlatform/kubernetes.`,
|
|
Run: runHelp,
|
|
BashCompletionFunction: bash_completion_func,
|
|
}
|
|
```
|
|
|
|
The `BashCompletionFunction` option is really only valid/useful on the root command. Doing the above will cause `__kubectl_custom_func()` (`__<command-use>_custom_func()`) to be called when the built in processor was unable to find a solution. In the case of kubernetes a valid command might look something like `kubectl get pod [mypod]`. If you type `kubectl get pod [tab][tab]` the `__kubectl_customc_func()` will run because the cobra.Command only understood "kubectl" and "get." `__kubectl_custom_func()` will see that the cobra.Command is "kubectl_get" and will thus call another helper `__kubectl_get_resource()`. `__kubectl_get_resource` will look at the 'nouns' collected. In our example the only noun will be `pod`. So it will call `__kubectl_parse_get pod`. `__kubectl_parse_get` will actually call out to kubernetes and get any pods. It will then set `COMPREPLY` to valid pods!
|
|
|
|
## Mark flags as required
|
|
|
|
Most of the time completions will only show subcommands. But if a flag is required to make a subcommand work, you probably want it to show up when the user types [tab][tab]. Marking a flag as 'Required' is incredibly easy.
|
|
|
|
```go
|
|
cmd.MarkFlagRequired("pod")
|
|
cmd.MarkFlagRequired("container")
|
|
```
|
|
|
|
and you'll get something like
|
|
|
|
```bash
|
|
# kubectl exec [tab][tab][tab]
|
|
-c --container= -p --pod=
|
|
```
|
|
|
|
# Specify valid filename extensions for flags that take a filename
|
|
|
|
In this example we use --filename= and expect to get a json or yaml file as the argument. To make this easier we annotate the --filename flag with valid filename extensions.
|
|
|
|
```go
|
|
annotations := []string{"json", "yaml", "yml"}
|
|
annotation := make(map[string][]string)
|
|
annotation[cobra.BashCompFilenameExt] = annotations
|
|
|
|
flag := &pflag.Flag{
|
|
Name: "filename",
|
|
Shorthand: "f",
|
|
Usage: usage,
|
|
Value: value,
|
|
DefValue: value.String(),
|
|
Annotations: annotation,
|
|
}
|
|
cmd.Flags().AddFlag(flag)
|
|
```
|
|
|
|
Now when you run a command with this filename flag you'll get something like
|
|
|
|
```bash
|
|
# kubectl create -f
|
|
test/ example/ rpmbuild/
|
|
hello.yml test.json
|
|
```
|
|
|
|
So while there are many other files in the CWD it only shows me subdirs and those with valid extensions.
|
|
|
|
# Specify custom flag completion
|
|
|
|
As for nouns, Cobra provides two ways of defining dynamic completion of flags. Note that both these methods can be used along-side each other as long as they are not both used for the same flag.
|
|
|
|
**Note**: *Custom Completions written in Go* will automatically work for other shell-completion scripts (e.g., Fish shell), while *Custom Completions written in Bash* will only work for Bash shell-completion. It is therefore recommended to use *Custom Completions written in Go*.
|
|
|
|
## 1. Custom completions of flags written in Go
|
|
|
|
To provide a Go function that Cobra will execute when it needs the list of completion choices for a flag, you must register the function in the following manner:
|
|
|
|
```go
|
|
flagName := "output"
|
|
cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
|
|
return []string{"json", "table", "yaml"}, cobra.ShellCompDirectiveDefault
|
|
})
|
|
```
|
|
Notice that calling `RegisterFlagCompletionFunc()` is done through the `command` with which the flag is associated. In our example this dynamic completion will give results like so:
|
|
|
|
```bash
|
|
# helm status --output [tab][tab]
|
|
json table yaml
|
|
```
|
|
|
|
### Debugging
|
|
|
|
You can also easily debug your Go completion code for flags:
|
|
```bash
|
|
# helm __complete status --output ""
|
|
json
|
|
table
|
|
yaml
|
|
:4
|
|
Completion ended with directive: ShellCompDirectiveNoFileComp # This is on stderr
|
|
```
|
|
***Important:*** You should **not** leave traces that print to stdout in your completion code as they will be interpreted as completion choices by the completion script. Instead, use the cobra-provided debugging traces functions mentioned in the above section.
|
|
|
|
## 2. Custom completions of flags written in Bash
|
|
|
|
Alternatively, you can use bash code for flag custom completion. Similar to the filename
|
|
completion and filtering using `cobra.BashCompFilenameExt`, you can specify
|
|
a custom flag completion bash function with `cobra.BashCompCustom`:
|
|
|
|
```go
|
|
annotation := make(map[string][]string)
|
|
annotation[cobra.BashCompCustom] = []string{"__kubectl_get_namespaces"}
|
|
|
|
flag := &pflag.Flag{
|
|
Name: "namespace",
|
|
Usage: usage,
|
|
Annotations: annotation,
|
|
}
|
|
cmd.Flags().AddFlag(flag)
|
|
```
|
|
|
|
In addition add the `__kubectl_get_namespaces` implementation in the `BashCompletionFunction`
|
|
value, e.g.:
|
|
|
|
```bash
|
|
__kubectl_get_namespaces()
|
|
{
|
|
local template
|
|
template="{{ range .items }}{{ .metadata.name }} {{ end }}"
|
|
local kubectl_out
|
|
if kubectl_out=$(kubectl get -o template --template="${template}" namespace 2>/dev/null); then
|
|
COMPREPLY=( $( compgen -W "${kubectl_out}[*]" -- "$cur" ) )
|
|
fi
|
|
}
|
|
```
|
|
# Using bash aliases for commands
|
|
|
|
You can also configure the `bash aliases` for the commands and they will also support completions.
|
|
|
|
```bash
|
|
alias aliasname=origcommand
|
|
complete -o default -F __start_origcommand aliasname
|
|
|
|
# and now when you run `aliasname` completion will make
|
|
# suggestions as it did for `origcommand`.
|
|
|
|
$) aliasname <tab><tab>
|
|
completion firstcommand secondcommand
|
|
```
|