Guess at config_id value so that updates don't break downstream resources.

.changelog/3723.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+`google_endpoints_service` now allows dependent resources to plan based on the `config_id` value.
+```

google/resource_endpoints_service.go

@@ -4,7 +4,11 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"log"
+	"regexp"
+	"strconv"
+	"strings"
 	"time"
 
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
@@ -141,9 +145,34 @@ func resourceEndpointsService() *schema.Resource {
 				},
 			},
 		},
+		CustomizeDiff: predictServiceId,
 	}
 }
 
+func predictServiceId(d *schema.ResourceDiff, meta interface{}) error {
+	if !d.HasChange("openapi_config") && !d.HasChange("grpc_config") && !d.HasChange("protoc_output_base64") {
+		return nil
+	}
+	loc, _ := time.LoadLocation("America/Los_Angeles")
+	baseDate := time.Now().In(loc).Format("2006-01-02")
+	oldConfigId := d.Get("config_id").(string)
+	if match, err := regexp.MatchString(`\d\d\d\d-\d\d-\d\dr\d*`, oldConfigId); !match || err != nil {
+		// If we do not match the expected format, we will guess
+		// wrong and that is worse than not guessing.
+		return nil
+	}
+	if strings.HasPrefix(oldConfigId, baseDate) {
+		n, err := strconv.Atoi(strings.Split(oldConfigId, "r")[1])
+		if err != nil {
+			return err
+		}
+		d.SetNew("config_id", fmt.Sprintf("%sr%d", baseDate, n+1))
+	} else {
+		d.SetNew("config_id", baseDate+"r0")
+	}
+	return nil
+}
+
 func getEndpointServiceOpenAPIConfigSource(configText string) *servicemanagement.ConfigSource {
 	// We need to provide a ConfigSource object to the API whenever submitting a
 	// new config.  A ConfigSource contains a ConfigFile which contains the b64

google/resource_endpoints_service_test.go

@@ -21,7 +21,15 @@ func TestAccEndpointsService_basic(t *testing.T) {
 		Providers:    testAccProviders,
 		Steps: []resource.TestStep{
 			{
-				Config: testAccEndpointsService_basic(serviceId, getTestProjectFromEnv()),
+				Config: testAccEndpointsService_basic(serviceId, getTestProjectFromEnv(), "1"),
+				Check:  testAccCheckEndpointExistsByName(t, serviceId),
+			},
+			{
+				Config: testAccEndpointsService_basic(serviceId, getTestProjectFromEnv(), "2"),
+				Check:  testAccCheckEndpointExistsByName(t, serviceId),
+			},
+			{
+				Config: testAccEndpointsService_basic(serviceId, getTestProjectFromEnv(), "3"),
 				Check:  testAccCheckEndpointExistsByName(t, serviceId),
 			},
 		},
@@ -97,7 +105,7 @@ func TestEndpointsService_grpcMigrateState(t *testing.T) {
 	}
 }
 
-func testAccEndpointsService_basic(serviceId, project string) string {
+func testAccEndpointsService_basic(serviceId, project, rev string) string {
 	return fmt.Sprintf(`
 resource "google_endpoints_service" "endpoints_service" {
   service_name   = "%[1]s.endpoints.%[2]s.cloud.goog"
@@ -106,7 +114,7 @@ resource "google_endpoints_service" "endpoints_service" {
 swagger: "2.0"
 info:
   description: "A simple Google Cloud Endpoints API example."
-  title: "Endpoints Example"
+  title: "Endpoints Example, rev. %[3]s"
   version: "1.0.0"
 host: "%[1]s.endpoints.%[2]s.cloud.goog"
 basePath: "/"
@@ -145,7 +153,14 @@ definitions:
 EOF
 
 }
-`, serviceId, project)
+
+resource "random_id" "foo" {
+  keepers = {
+    config_id = google_endpoints_service.endpoints_service.config_id
+  }
+  byte_length = 8
+}
+`, serviceId, project, rev)
 }
 
 func testAccEndpointsService_grpc(serviceId, project string) string {