Set google_service_account IAM-related fields during plan stage

.changelog/11929.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+resourcemanager: made `google_service_account` `email` and `member` fields available during plan
+```

google/services/resourcemanager/resource_google_service_account.go

@@ -3,7 +3,9 @@
 package resourcemanager
 
 import (
+	"context"
 	"fmt"
+	"log"
 	"strings"
 	"time"
 
@@ -32,6 +34,7 @@ func ResourceGoogleServiceAccount() *schema.Resource {
 		},
 		CustomizeDiff: customdiff.All(
 			tpgresource.DefaultProviderProject,
+			resourceServiceAccountCustomDiff,
 		),
 		Schema: map[string]*schema.Schema{
 			"email": {
@@ -324,3 +327,34 @@ func resourceGoogleServiceAccountImport(d *schema.ResourceData, meta interface{}
 
 	return []*schema.ResourceData{d}, nil
 }
+
+func ResourceServiceAccountCustomDiffFunc(diff tpgresource.TerraformResourceDiff) error {
+	if !tpgresource.IsNewResource(diff) && !diff.HasChange("account_id") {
+		return nil
+	}
+
+	aid := diff.Get("account_id").(string)
+	proj := diff.Get("project").(string)
+	if aid == "" || proj == "" {
+		return nil
+	}
+
+	email := fmt.Sprintf("%s@%s.iam.gserviceaccount.com", aid, proj)
+	if err := diff.SetNew("email", email); err != nil {
+		return fmt.Errorf("error setting email: %s", err)
+	}
+	if err := diff.SetNew("member", "serviceAccount:"+email); err != nil {
+		return fmt.Errorf("error setting member: %s", err)
+	}
+
+	return nil
+}
+func resourceServiceAccountCustomDiff(_ context.Context, diff *schema.ResourceDiff, meta interface{}) error {
+	if ud := transport_tpg.GetUniverseDomainFromMeta(meta); ud != "googleapis.com" {
+		log.Printf("[WARN] The UniverseDomain is set to %q. Skipping resourceServiceAccountCustomDiff", ud)
+		return nil
+	}
+
+	// separate func to allow unit testing
+	return ResourceServiceAccountCustomDiffFunc(diff)
+}

google/services/resourcemanager/resource_google_service_account_test.go

@@ -4,12 +4,16 @@ package resourcemanager_test
 
 import (
 	"fmt"
+	"maps"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/terraform-plugin-testing/helper/resource"
 	"github.com/hashicorp/terraform-plugin-testing/terraform"
 	"github.com/hashicorp/terraform-provider-google/google/acctest"
 	"github.com/hashicorp/terraform-provider-google/google/envvar"
+	tpgresourcemanager "github.com/hashicorp/terraform-provider-google/google/services/resourcemanager"
+	"github.com/hashicorp/terraform-provider-google/google/tpgresource"
 )
 
 // Test that a service account resource can be created, updated, and destroyed
@@ -301,3 +305,107 @@ resource "google_service_account" "acceptance" {
 }
 `, account, name, desc, disabled)
 }
+
+func TestResourceServiceAccountCustomDiff(t *testing.T) {
+	t.Parallel()
+
+	accountId := "a" + acctest.RandString(t, 10)
+	project := envvar.GetTestProjectFromEnv()
+	if project == "" {
+		project = "test-project"
+	}
+	expectedEmail := fmt.Sprintf("%s@%s.iam.gserviceaccount.com", accountId, project)
+	expectedMember := "serviceAccount:" + expectedEmail
+
+	cases := []struct {
+		name       string
+		before     map[string]interface{}
+		after      map[string]interface{}
+		wantEmail  string
+		wantMember string
+	}{
+		{
+			name:   "normal (new)",
+			before: map[string]interface{}{},
+			after: map[string]interface{}{
+				"account_id": accountId,
+				"name":       "", // Empty name indicates a new resource
+				"project":    project,
+			},
+			wantEmail:  expectedEmail,
+			wantMember: expectedMember,
+		},
+		{
+			name: "no change",
+			before: map[string]interface{}{
+				"account_id": accountId,
+				"email":      "dontchange",
+				"member":     "dontchange",
+				"project":    project,
+			},
+			after: map[string]interface{}{
+				"account_id": accountId,
+				"name":       "unimportant",
+				"project":    project,
+			},
+			wantEmail:  "",
+			wantMember: "",
+		},
+		{
+			name: "recreate (new)",
+			before: map[string]interface{}{
+				"account_id": "recreate-account",
+				"email":      "recreate-email",
+				"member":     "recreate-member",
+				"project":    project,
+			},
+			after: map[string]interface{}{
+				"account_id": accountId,
+				"name":       "",
+				"project":    project,
+			},
+			wantEmail:  expectedEmail,
+			wantMember: expectedMember,
+		},
+		{
+			name:   "missing account_id (new)",
+			before: map[string]interface{}{},
+			after: map[string]interface{}{
+				"account_id": "",
+				"name":       "",
+				"project":    project,
+			},
+			wantEmail:  "",
+			wantMember: "",
+		},
+		{
+			name:   "missing project (new)",
+			before: map[string]interface{}{},
+			after: map[string]interface{}{
+				"account_id": accountId,
+				"name":       "",
+				"project":    "",
+			},
+			wantEmail:  "",
+			wantMember: "",
+		},
+	}
+	for _, tc := range cases {
+		result := maps.Clone(tc.after)
+		if tc.wantEmail != "" || tc.wantMember != "" {
+			result["email"] = tc.wantEmail
+			result["member"] = tc.wantMember
+		}
+		t.Run(tc.name, func(t *testing.T) {
+			diff := &tpgresource.ResourceDiffMock{
+				Before: tc.before,
+				After:  tc.after,
+				Schema: tpgresourcemanager.ResourceGoogleServiceAccount().Schema,
+			}
+			tpgresourcemanager.ResourceServiceAccountCustomDiffFunc(diff)
+			if d := cmp.Diff(result, diff.After); d != "" {
+				t.Fatalf("got unexpected change: %v expected: %v", diff.After, result)
+			}
+		})
+	}
+}

google/tpgresource/resource_test_utils.go

@@ -81,6 +81,7 @@ type ResourceDiffMock struct {
 	Before     map[string]interface{}
 	After      map[string]interface{}
 	Cleared    map[string]interface{}
+	Schema     map[string]*schema.Schema
 	IsForceNew bool
 }
 
@@ -115,6 +116,32 @@ func (d *ResourceDiffMock) ForceNew(key string) error {
 	return nil
 }
 
+func (d *ResourceDiffMock) SetNew(key string, value interface{}) error {
+	if len(d.Schema) > 0 {
+		if err := d.checkKey(key, "SetNew"); err != nil {
+			return err
+		}
+	}
+
+	d.After[key] = value
+	return nil
+}
+
+func (d *ResourceDiffMock) checkKey(key, caller string) error {
+	var schema *schema.Schema
+	s, ok := d.Schema[key]
+	if ok {
+		schema = s
+	}
+	if schema == nil {
+		return fmt.Errorf("%s: invalid key: %s", caller, key)
+	}
+	if !schema.Computed {
+		return fmt.Errorf("%s only operates on computed keys - %s is not one", caller, key)
+	}
+	return nil
+}
+
 // This function isn't a test of transport.go; instead, it is used as an alternative
 // to ReplaceVars inside tests.
 func ReplaceVarsForTest(config *transport_tpg.Config, rs *terraform.ResourceState, linkTmpl string) (string, error) {

google/tpgresource/utils.go

@@ -56,6 +56,7 @@ type TerraformResourceDiff interface {
 	GetOk(string) (interface{}, bool)
 	Clear(string) error
 	ForceNew(string) error
+	SetNew(string, interface{}) error
 }
 
 // Contains functions that don't really belong anywhere else.

google/transport/config.go

@@ -2449,3 +2449,11 @@ func GetRegionFromRegionSelfLink(selfLink string) string {
 	}
 	return selfLink
 }
+
+func GetUniverseDomainFromMeta(meta interface{}) string {
+	config := meta.(*Config)
+	if config.UniverseDomain == "" {
+		return "googleapis.com"
+	}
+	return config.UniverseDomain
+}