cmd: Introduce version JSON output (hashicorp#386)

internal/cmd/version_command.go

@@ -0,0 +1,68 @@
+package cmd
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/mitchellh/cli"
+)
+
+type VersionOutput struct {
+	Version string `json:"version"`
+}
+
+type VersionCommand struct {
+	Ui      cli.Ui
+	Version string
+
+	jsonOutput bool
+}
+
+func (c *VersionCommand) flags() *flag.FlagSet {
+	fs := defaultFlagSet("version")
+
+	fs.BoolVar(&c.jsonOutput, "json", false, "output the version information as a JSON object")
+
+	fs.Usage = func() { c.Ui.Error(c.Help()) }
+
+	return fs
+}
+
+func (c *VersionCommand) Run(args []string) int {
+	f := c.flags()
+	if err := f.Parse(args); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error parsing command-line flags: %s", err))
+		return 1
+	}
+
+	if c.jsonOutput {
+		output := VersionOutput{
+			Version: c.Version,
+		}
+		jsonOutput, err := json.MarshalIndent(output, "", "  ")
+		if err != nil {
+			c.Ui.Error(fmt.Sprintf("\nError marshalling JSON: %s", err))
+			return 1
+		}
+		c.Ui.Output(string(jsonOutput))
+		return 0
+	}
+
+	c.Ui.Output(string(c.Version))
+	return 0
+}
+
+func (c *VersionCommand) Help() string {
+	helpText := `
+Usage: terraform-ls version [-json]
+
+` + c.Synopsis() + "\n\n" + helpForFlags(c.flags())
+
+	return strings.TrimSpace(helpText)
+}
+
+func (c *VersionCommand) Synopsis() string {
+	return "Displays the version of the language server"
+}

main.go

@@ -43,6 +43,12 @@ func main() {
 				Ui: ui,
 			}, nil
 		},
+		"version": func() (cli.Command, error) {
+			return &cmd.VersionCommand{
+				Ui:      ui,
+				Version: VersionString(),
+			}, nil
+		},
 	}
 
 	exitStatus, err := c.Run()