Add logging to pinpoint problem, restore crash.

Add logging that will catch the bug red-handed, hopefully, or at least
give us more details if our understanding of the bug is off. Also,
restore the crash behavior so we can see where it fits in with the logs.

helper/schema/grpc_provider.go

@@ -796,10 +796,7 @@ func (s *GRPCProviderServer) PlanResourceChange(ctx context.Context, req *tfprot
 	newExtra := map[string]interface{}{}
 
 	for k, v := range diff.Attributes {
-		if v == nil {
-			log.Printf("[WARN] Field %q was null, not modifying its NewExtra", k)
-			continue
-		}
+		log.Printf("[TRACE] tpg-7934: copying over attribute %q", k)
 		if v.NewExtra != nil {
 			newExtra[k] = v.NewExtra
 		}

helper/schema/resource_diff.go

@@ -3,6 +3,7 @@ package schema
 import (
 	"errors"
 	"fmt"
+	"log"
 	"reflect"
 	"strings"
 	"sync"
@@ -461,9 +462,11 @@ func (d *ResourceDiff) getChange(key string) (getResult, getResult, bool) {
 	var new getResult
 	for p := range d.updatedKeys {
 		if childAddrOf(key, p) {
+			log.Printf("[TRACE] tpg-7934: key %q is child of parent %q, counts as computed", key, p)
 			new = d.getExact(strings.Split(key, "."), "newDiff")
 			return old, new, true
 		}
+		log.Printf("[TRACE] tpg-7934: key %q is not child of parent %q, does not count as computed", key, p)
 	}
 	new = d.get(strings.Split(key, "."), "newDiff")
 	return old, new, false

helper/schema/schema.go

@@ -360,6 +360,7 @@ func (s *Schema) ZeroValue() interface{} {
 
 func (s *Schema) finalizeDiff(d *terraform.ResourceAttrDiff, customized bool) *terraform.ResourceAttrDiff {
 	if d == nil {
+		log.Println("[TRACE] tpg-7934: returning nil from finalizeDiff because nil was passed in")
 		return d
 	}
 
@@ -408,6 +409,7 @@ func (s *Schema) finalizeDiff(d *terraform.ResourceAttrDiff, customized bool) *t
 			if d.Old != "" && d.New == "" {
 				// This is a computed value with an old value set already,
 				// just let it go.
+				log.Println("[TRACE] tpg-7934: returning nil from finalizeDiff because customized")
 				return nil
 			}
 		}
@@ -1383,6 +1385,7 @@ func (m schemaMap) diffString(
 		return nil
 	}
 
+	log.Printf("[TRACE] tpg-7934: setting attribute %q", k)
 	diff.Attributes[k] = schema.finalizeDiff(
 		&terraform.ResourceAttrDiff{
 			Old:         os,