From 6913754191e080a98741c176ad6004c07ee2c892 Mon Sep 17 00:00:00 2001
From: James Nugent <james@jen20.com>
Date: Fri, 29 Apr 2016 18:42:24 -0500
Subject: [PATCH] provider/docker: don't crash with empty commands

If any of the entries in `commands` on `docker_container` resources was
empty, the assertion to string panic'd. Since we can't use ValidateFunc
on list elements, we can only really check this at apply time. If any
value is nil (resolves to empty string during conversion), we fail with
an error prior to creating the container.

Fixes #6409.
---
 .../providers/docker/resource_docker_container_funcs.go  | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/builtin/providers/docker/resource_docker_container_funcs.go b/builtin/providers/docker/resource_docker_container_funcs.go
index 00090294c..b475884b6 100644
--- a/builtin/providers/docker/resource_docker_container_funcs.go
+++ b/builtin/providers/docker/resource_docker_container_funcs.go
@@ -51,6 +51,11 @@ func resourceDockerContainerCreate(d *schema.ResourceData, meta interface{}) err
 
 	if v, ok := d.GetOk("command"); ok {
 		createOpts.Config.Cmd = stringListToStringSlice(v.([]interface{}))
+		for _, v := range createOpts.Config.Cmd {
+			if v == "" {
+				return fmt.Errorf("values for command may not be empty")
+			}
+		}
 	}
 
 	if v, ok := d.GetOk("entrypoint"); ok {
@@ -269,6 +274,10 @@ func resourceDockerContainerDelete(d *schema.ResourceData, meta interface{}) err
 func stringListToStringSlice(stringList []interface{}) []string {
 	ret := []string{}
 	for _, v := range stringList {
+		if v == nil {
+			ret = append(ret, "")
+			continue
+		}
 		ret = append(ret, v.(string))
 	}
 	return ret