command: show shadow errors to the user

command/apply.go

@@ -136,6 +136,9 @@ func (c *ApplyCommand) Run(args []string) int {
 		}
 	}
 
+	// This is going to keep track of shadow errors
+	var shadowErr error
+
 	// Build the context based on the arguments given
 	ctx, planned, err := c.Context(contextOpts{
 		Destroy:     c.Destroy,
@@ -189,6 +192,12 @@ func (c *ApplyCommand) Run(args []string) int {
 			c.Ui.Error(fmt.Sprintf("Error configuring: %s", err))
 			return 1
 		}
+
+		// Record any shadow errors for later
+		if err := ctx.ShadowError(); err != nil {
+			shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+				err, "input operation:"))
+		}
 	}
 	if !validateContext(ctx, c.Ui) {
 		return 1
@@ -208,6 +217,12 @@ func (c *ApplyCommand) Run(args []string) int {
 				"Error creating plan: %s", err))
 			return 1
 		}
+
+		// Record any shadow errors for later
+		if err := ctx.ShadowError(); err != nil {
+			shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+				err, "plan operation:"))
+		}
 	}
 
 	// Setup the state hook for continuous state updates
@@ -229,6 +244,12 @@ func (c *ApplyCommand) Run(args []string) int {
 	go func() {
 		defer close(doneCh)
 		state, applyErr = ctx.Apply()
+
+		// Record any shadow errors for later
+		if err := ctx.ShadowError(); err != nil {
+			shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+				err, "apply operation:"))
+		}
 	}()
 
 	// Wait for the apply to finish or for us to be interrupted so
@@ -304,6 +325,9 @@ func (c *ApplyCommand) Run(args []string) int {
 		}
 	}
 
+	// If we have an error in the shadow graph, let the user know.
+	c.outputShadowError(shadowErr, applyErr == nil)
+
 	return 0
 }
 

command/meta.go

@@ -460,6 +460,42 @@ func (m *Meta) addModuleDepthFlag(flags *flag.FlagSet, moduleDepth *int) {
 	}
 }
 
+// outputShadowError outputs the error from ctx.ShadowError. If the
+// error is nil then nothing happens. If output is false then it isn't
+// outputted to the user (you can define logic to guard against outputting).
+func (m *Meta) outputShadowError(err error, output bool) bool {
+	// Do nothing if no error
+	if err == nil {
+		return false
+	}
+
+	// If not outputting, do nothing
+	if !output {
+		return false
+	}
+
+	// Output!
+	m.Ui.Output(m.Colorize().Color(fmt.Sprintf(
+		"[reset][bold][yellow]\nExperimental feature failure! Please report a bug.\n\n"+
+			"This is not an error. Your Terraform operation completed successfully.\n"+
+			"Your real infrastructure is unaffected by this message.\n\n"+
+			"[reset][yellow]While running, Terraform sometimes tests experimental features in the\n"+
+			"background. These features cannot affect real state and never touch\n"+
+			"real infrastructure. If the features work properly, you see nothing.\n"+
+			"If the features fail, this message appears.\n\n"+
+			"The following failures happened while running experimental features.\n"+
+			"Please report a Terraform bug so that future Terraform versions that\n"+
+			"enable these features can be improved!\n\n"+
+			"You can report an issue at: https://github.com/hashicorp/terraform/issues\n\n"+
+			"%s\n\n"+
+			"This is not an error. Your terraform operation completed successfully\n"+
+			"and your real infrastructure is unaffected by this message.",
+		err,
+	)))
+
+	return true
+}
+
 // contextOpts are the options used to load a context from a command.
 type contextOpts struct {
 	// Path to the directory where the root module is.

command/plan.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -57,6 +58,9 @@ func (c *PlanCommand) Run(args []string) int {
 	countHook := new(CountHook)
 	c.Meta.extraHooks = []terraform.Hook{countHook}
 
+	// This is going to keep track of shadow errors
+	var shadowErr error
+
 	ctx, _, err := c.Context(contextOpts{
 		Destroy:     destroy,
 		Path:        path,
@@ -73,6 +77,12 @@ func (c *PlanCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Record any shadow errors for later
+	if err := ctx.ShadowError(); err != nil {
+		shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+			err, "input operation:"))
+	}
+
 	if !validateContext(ctx, c.Ui) {
 		return 1
 	}
@@ -138,6 +148,15 @@ func (c *PlanCommand) Run(args []string) int {
 		countHook.ToChange,
 		countHook.ToRemove+countHook.ToRemoveAndAdd)))
 
+	// Record any shadow errors for later
+	if err := ctx.ShadowError(); err != nil {
+		shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+			err, "plan operation:"))
+	}
+
+	// If we have an error in the shadow graph, let the user know.
+	c.outputShadowError(shadowErr, true)
+
 	if detailed {
 		return 2
 	}

command/refresh.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -79,6 +80,9 @@ func (c *RefreshCommand) Run(args []string) int {
 		}
 	}
 
+	// This is going to keep track of shadow errors
+	var shadowErr error
+
 	// Build the context based on the arguments given
 	ctx, _, err := c.Context(contextOpts{
 		Path:        configPath,
@@ -95,6 +99,12 @@ func (c *RefreshCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Record any shadow errors for later
+	if err := ctx.ShadowError(); err != nil {
+		shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+			err, "input operation:"))
+	}
+
 	if !validateContext(ctx, c.Ui) {
 		return 1
 	}
@@ -115,6 +125,15 @@ func (c *RefreshCommand) Run(args []string) int {
 		c.Ui.Output(c.Colorize().Color(outputs))
 	}
 
+	// Record any shadow errors for later
+	if err := ctx.ShadowError(); err != nil {
+		shadowErr = multierror.Append(shadowErr, multierror.Prefix(
+			err, "refresh operation:"))
+	}
+
+	// If we have an error in the shadow graph, let the user know.
+	c.outputShadowError(shadowErr, true)
+
 	return 0
 }