generated func now validates based on data provided in context, which needs to include the future values if it is to be interpolated properly.

common/step_provision.go

@@ -53,10 +53,6 @@ func PlaceholderData() map[string]string {
 	return placeholderData
 }
 
-type StepProvision struct {
-	Comm packer.Communicator
-}
-
 func PopulateProvisionHookData(state multistep.StateBag) map[string]interface{} {
 	hookData := map[string]interface{}{}
 	// Read communicator data into hook data
@@ -76,13 +72,24 @@ func PopulateProvisionHookData(state multistep.StateBag) map[string]interface{}
 	}
 	// Loop over all field values and retrieve them from the ssh config
 	for fieldName, _ := range pd {
+		if fieldName == "ID" {
+			continue
+		}
 		fVal := v.FieldByName(fieldName)
+		if fVal.IsZero() {
+			log.Printf("Megan NONINTERFACABLE fVal is %#v", fVal)
+		} else {
 			hookData[fieldName] = fVal.Interface()
 		}
+	}
 
 	return hookData
 }
 
+type StepProvision struct {
+	Comm packer.Communicator
+}
+
 func (s *StepProvision) runWithHook(ctx context.Context, state multistep.StateBag, hooktype string) multistep.StepAction {
 	// hooktype will be either packer.HookProvision or packer.HookCleanupProvision
 	comm := s.Comm

template/interpolate/funcs.go

@@ -3,6 +3,7 @@ package interpolate
 import (
 	"errors"
 	"fmt"
+	"log"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -164,9 +165,21 @@ func funcGenTemplateDir(ctx *Context) interface{} {
 }
 
 func funcGenGenerated(ctx *Context) interface{} {
-	return func(k string) (string, error) {
-		// Return the key inside braces _without_ the generated func attached
-		return fmt.Sprintf("{{.%s}}", k), nil
+	return func(s string) (string, error) {
+		log.Printf("Megan context data is %#v", ctx.Data)
+		if data, ok := ctx.Data.(map[string]string); ok {
+			// PlaceholderData has been passed into generator, and we can check
+			// the value against the placeholder data to make sure that it is
+			// valid
+			if heldPlace, ok := data[s]; ok {
+				return heldPlace, nil
+			} else {
+				return "", fmt.Errorf("loaded data, but couldnt find winrm in it", s)
+			}
+		}
+
+		return "", fmt.Errorf("Error validating computed variable: the given "+
+			"variable %s will not be passed into your plugin.", s)
 	}
 }