Improving command line interface (#4689)

1 files changed, 206 insertions, 0 deletions

diff --git a/vendor/github.com/spf13/cobra/bash_completions.md b/vendor/github.com/spf13/cobra/bash_completions.md
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+# Generating Bash Completions For Your Own cobra.Command
+
+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"
+
+        "github.com/GoogleCloudPlatform/kubernetes/pkg/kubectl/cmd"
+)
+
+func main() {
+        kubectl := cmd.NewFactory(nil).NewKubectlCommand(os.Stdin, ioutil.Discard, ioutil.Discard)
+        kubectl.GenBashCompletionFile("out.sh")
+}
+```
+
+That will get you completions of subcommands and flags. If you make additional annotations to your code, you can get even more intelligent and flexible behavior.
+
+## Creating your own custom functions
+
+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
+}
+
+__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 `__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 `__customc_func()` will run because the cobra.Command only understood "kubectl" and "get." `__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!
+
+## Have the completions code complete your 'nouns'
+
+In the above example "pod" was assumed to already be typed. But 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.
+
+## 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.
+
+# Specifiy custom flag completion
+
+Similar to the filename completion and filtering using cobra.BashCompFilenameExt, you can specifiy
+a custom flag completion function with cobra.BashCompCustom:
+
+```go
+	annotation := make(map[string][]string)
+	annotation[cobra.BashCompFilenameExt] = []string{"__kubectl_get_namespaces"}
+
+	flag := &pflag.Flag{
+		Name:        "namespace",
+		Usage:       usage,
+		Annotations: annotation,
+	}
+	cmd.Flags().AddFlag(flag)
+```
+
+In addition add the `__handle_namespace_flag` 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
+}
+```