[WIP] command: Add terraform untaint

 - [x] Command Unit Tests
 - [x] Docs
 - [ ] State Unit Tests

Closes #4820

command/command_test.go

@@ -202,7 +202,7 @@ func testStateOutput(t *testing.T, path string, expected string) {
 	actual := strings.TrimSpace(newState.String())
 	expected = strings.TrimSpace(expected)
 	if actual != expected {
-		t.Fatalf("bad:\n\n%s", actual)
+		t.Fatalf("expected:\n%s\nactual:\n%s", expected, actual)
 	}
 }
 

command/untaint.go

@@ -0,0 +1,186 @@
+package command
+
+import (
+	"fmt"
+	"log"
+	"strings"
+)
+
+// UntaintCommand is a cli.Command implementation that manually untaints
+// a resource, marking it as primary and ready for service.
+type UntaintCommand struct {
+	Meta
+}
+
+func (c *UntaintCommand) Run(args []string) int {
+	args = c.Meta.process(args, false)
+
+	var allowMissing bool
+	var module string
+	var index int
+	cmdFlags := c.Meta.flagSet("taint")
+	cmdFlags.BoolVar(&allowMissing, "allow-missing", false, "module")
+	cmdFlags.StringVar(&module, "module", "", "module")
+	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
+	cmdFlags.StringVar(&c.Meta.stateOutPath, "state-out", "", "path")
+	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
+	cmdFlags.IntVar(&index, "index", -1, "index")
+	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
+	if err := cmdFlags.Parse(args); err != nil {
+		return 1
+	}
+
+	// Require the one argument for the resource to taint
+	args = cmdFlags.Args()
+	if len(args) != 1 {
+		c.Ui.Error("The untaint command expects exactly one argument.")
+		cmdFlags.Usage()
+		return 1
+	}
+
+	name := args[0]
+	if module == "" {
+		module = "root"
+	} else {
+		module = "root." + module
+	}
+
+	// Get the state that we'll be modifying
+	state, err := c.State()
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Failed to load state: %s", err))
+		return 1
+	}
+
+	// Get the actual state structure
+	s := state.State()
+	if s.Empty() {
+		if allowMissing {
+			return c.allowMissingExit(name, module)
+		}
+
+		c.Ui.Error(fmt.Sprintf(
+			"The state is empty. The most common reason for this is that\n" +
+				"an invalid state file path was given or Terraform has never\n " +
+				"been run for this infrastructure. Infrastructure must exist\n" +
+				"for it to be untainted."))
+		return 1
+	}
+
+	// Get the proper module we want to taint
+	modPath := strings.Split(module, ".")
+	mod := s.ModuleByPath(modPath)
+	if mod == nil {
+		if allowMissing {
+			return c.allowMissingExit(name, module)
+		}
+
+		c.Ui.Error(fmt.Sprintf(
+			"The module %s could not be found. There is nothing to taint.",
+			module))
+		return 1
+	}
+
+	// If there are no resources in this module, it is an error
+	if len(mod.Resources) == 0 {
+		if allowMissing {
+			return c.allowMissingExit(name, module)
+		}
+
+		c.Ui.Error(fmt.Sprintf(
+			"The module %s has no resources. There is nothing to taint.",
+			module))
+		return 1
+	}
+
+	// Get the resource we're looking for
+	rs, ok := mod.Resources[name]
+	if !ok {
+		if allowMissing {
+			return c.allowMissingExit(name, module)
+		}
+
+		c.Ui.Error(fmt.Sprintf(
+			"The resource %s couldn't be found in the module %s.",
+			name,
+			module))
+		return 1
+	}
+
+	// Untaint the resource
+	if err := rs.Untaint(index); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error untainting %s: %s", name, err))
+		c.Ui.Error("You can use `terraform show` to inspect the current state.")
+		return 1
+	}
+
+	log.Printf("[INFO] Writing state output to: %s", c.Meta.StateOutPath())
+	if err := c.Meta.PersistState(s); err != nil {
+		c.Ui.Error(fmt.Sprintf("Error writing state file: %s", err))
+		return 1
+	}
+
+	c.Ui.Output(fmt.Sprintf(
+		"The resource %s in the module %s has been marked as tainted!",
+		name, module))
+	return 0
+}
+
+func (c *UntaintCommand) Help() string {
+	helpText := `
+Usage: terraform untaint [options] name
+
+  Manually unmark a resource as tainted, restoring it as the primary
+	instance in the state.  This reverses either a manual 'terraform taint' or
+	the result of provisioners failing on a resource.
+
+  This will not modify your infrastructure. This command changes your
+  state to unmark a resource as tainted so that during the next plan or
+  apply, that resource will be destroyed and recreated. This command on
+  its own will not modify infrastructure. This command can be undone by
+  reverting the state backup file that is created, or by running
+  'terraform taint' on the resource.
+
+Options:
+
+  -allow-missing      If specified, the command will succeed (exit code 0)
+                      even if the resource is missing.
+
+  -backup=path        Path to backup the existing state file before
+                      modifying. Defaults to the "-state-out" path with
+                      ".backup" extension. Set to "-" to disable backup.
+
+  -index=n            Selects a single tainted instance when there are more
+                      than one tainted instances present in the state for a
+                      given resource. This flag is required when multiple
+                      tainted instances are present. The vast majority of the
+                      time, there is a maxiumum of one tainted instance per
+                      resource, so this flag can be safely omitted.
+
+  -module=path        The module path where the resource lives. By
+                      default this will be root. Child modules can be specified
+                      by names. Ex. "consul" or "consul.vpc" (nested modules).
+
+  -no-color           If specified, output won't contain any color.
+
+  -state=path         Path to read and save state (unless state-out
+                      is specified). Defaults to "terraform.tfstate".
+
+  -state-out=path     Path to write updated state file. By default, the
+                      "-state" path will be used.
+
+`
+	return strings.TrimSpace(helpText)
+}
+
+func (c *UntaintCommand) Synopsis() string {
+	return "Manually unmark a resource as tainted"
+}
+
+func (c *UntaintCommand) allowMissingExit(name, module string) int {
+	c.Ui.Output(fmt.Sprintf(
+		"The resource %s in the module %s was not found, but\n"+
+			"-allow-missing is set, so we're exiting successfully.",
+		name, module))
+	return 0
+}