Add metadata functions command skeleton

commands.go

@@ -207,6 +207,12 @@ func initCommands(
 			}, nil
 		},
 
+		"metadata functions": func() (cli.Command, error) {
+			return &command.MetadataFunctionsCommand{
+				Meta: meta,
+			}, nil
+		},
+
 		"output": func() (cli.Command, error) {
 			return &command.OutputCommand{
 				Meta: meta,

internal/command/metadata_functions.go

@@ -0,0 +1,47 @@
+package command
+
+import (
+	"fmt"
+)
+
+// MetadataFunctionsCommand is a Command implementation that prints out information
+// about the available functions in Terraform.
+type MetadataFunctionsCommand struct {
+	Meta
+}
+
+func (c *MetadataFunctionsCommand) Help() string {
+	return metadataFunctionsCommandHelp
+}
+
+func (c *MetadataFunctionsCommand) Synopsis() string {
+	return "Show signatures and descriptions for the available functions"
+}
+
+func (c *MetadataFunctionsCommand) Run(args []string) int {
+	args = c.Meta.process(args)
+	cmdFlags := c.Meta.defaultFlagSet("metadata functions")
+	var jsonOutput bool
+	cmdFlags.BoolVar(&jsonOutput, "json", false, "produce JSON output")
+
+	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
+	if err := cmdFlags.Parse(args); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error parsing command-line flags: %s\n", err.Error()))
+		return 1
+	}
+
+	if !jsonOutput {
+		c.Ui.Error(
+			"The `terraform metadata functions` command requires the `-json` flag.\n")
+		cmdFlags.Usage()
+		return 1
+	}
+
+	return 0
+}
+
+const metadataFunctionsCommandHelp = `
+Usage: terraform [global options] metadata functions -json
+
+  Prints out a json representation of the available function signatures.
+`