helper/schema: validate ConflictsWith against top-level

The runtime impl of ConfictsWith uses Resource.Get(), which makes it
work with any other attribute of the resource - the InternalValidate was
only checking against the local schemaMap though, preventing subResource
from using ConflictsWith properly.

It's a lot of wiring and it's a bit ugly, but it's not runtime code, so
I'm a bit less concerned about that aspect.

This should take care of the problem mentioned in #1909

helper/schema/provider.go

@@ -61,12 +61,13 @@ func (p *Provider) InternalValidate() error {
 		return errors.New("provider is nil")
 	}
 
-	if err := schemaMap(p.Schema).InternalValidate(); err != nil {
+	sm := schemaMap(p.Schema)
+	if err := sm.InternalValidate(sm); err != nil {
 		return err
 	}
 
 	for k, r := range p.ResourcesMap {
-		if err := r.InternalValidate(); err != nil {
+		if err := r.InternalValidate(nil); err != nil {
 			return fmt.Errorf("%s: %s", k, err)
 		}
 	}

helper/schema/resource.go

@@ -220,10 +220,11 @@ func (r *Resource) Refresh(
 // Provider.InternalValidate() will automatically call this for all of
 // the resources it manages, so you don't need to call this manually if it
 // is part of a Provider.
-func (r *Resource) InternalValidate() error {
+func (r *Resource) InternalValidate(topSchemaMap schemaMap) error {
 	if r == nil {
 		return errors.New("resource is nil")
 	}
+	tsm := topSchemaMap
 
 	if r.isTopLevel() {
 		// All non-Computed attributes must be ForceNew if Update is not defined
@@ -239,9 +240,10 @@ func (r *Resource) InternalValidate() error {
 					"No Update defined, must set ForceNew on: %#v", nonForceNewAttrs)
 			}
 		}
+		tsm = schemaMap(r.Schema)
 	}
 
-	return schemaMap(r.Schema).InternalValidate()
+	return schemaMap(r.Schema).InternalValidate(tsm)
 }
 
 // Returns true if the resource is "top level" i.e. not a sub-resource.

helper/schema/schema.go

@@ -17,6 +17,7 @@ import (
 	"reflect"
 	"sort"
 	"strconv"
+	"strings"
 
 	"github.com/hashicorp/terraform/terraform"
 	"github.com/mitchellh/mapstructure"
@@ -410,7 +411,10 @@ func (m schemaMap) Validate(c *terraform.ResourceConfig) ([]string, []error) {
 // InternalValidate validates the format of this schema. This should be called
 // from a unit test (and not in user-path code) to verify that a schema
 // is properly built.
-func (m schemaMap) InternalValidate() error {
+func (m schemaMap) InternalValidate(topSchemaMap schemaMap) error {
+	if topSchemaMap == nil {
+		topSchemaMap = m
+	}
 	for k, v := range m {
 		if v.Type == TypeInvalid {
 			return fmt.Errorf("%s: Type must be specified", k)
@@ -446,11 +450,32 @@ func (m schemaMap) InternalValidate() error {
 
 		if len(v.ConflictsWith) > 0 {
 			for _, key := range v.ConflictsWith {
-				if m[key].Required {
+				parts := strings.Split(key, ".")
+				sm := topSchemaMap
+				var target *Schema
+				for _, part := range parts {
+					// Skip index fields
+					if _, err := strconv.Atoi(part); err == nil {
+						continue
+					}
+
+					var ok bool
+					if target, ok = sm[part]; !ok {
+						return fmt.Errorf("%s: ConflictsWith references unknown attribute (%s)", k, key)
+					}
+
+					if subResource, ok := target.Elem.(*Resource); ok {
+						sm = schemaMap(subResource.Schema)
+					}
+				}
+				if target == nil {
+					return fmt.Errorf("%s: ConflictsWith cannot find target attribute (%s), sm: %#v", k, key, sm)
+				}
+				if target.Required {
 					return fmt.Errorf("%s: ConflictsWith cannot contain Required attribute (%s)", k, key)
 				}
 
-				if m[key].Computed || len(m[key].ComputedWhen) > 0 {
+				if target.Computed || len(target.ComputedWhen) > 0 {
 					return fmt.Errorf("%s: ConflictsWith cannot contain Computed(When) attribute (%s)", k, key)
 				}
 			}
@@ -473,7 +498,7 @@ func (m schemaMap) InternalValidate() error {
 
 			switch t := v.Elem.(type) {
 			case *Resource:
-				if err := t.InternalValidate(); err != nil {
+				if err := t.InternalValidate(topSchemaMap); err != nil {
 					return err
 				}
 			case *Schema: