fix(application): handle storage details conversion error

- Added error handling for "cannot convert storage details"
  in `applicationsClient.ReadApplication`.
- Improved retry logic for storage readiness in `ReadApplicationWithRetryOnNotFound`.

This commit ensures that the application correctly handles storage conversion errors and retries
appropriately until the storage is ready.

internal/juju/applications.go

@@ -762,6 +762,18 @@ func (c applicationsClient) ReadApplicationWithRetryOnNotFound(ctx context.Conte
 				c.Errorf(err, fmt.Sprintf("ReadApplicationWithRetryOnNotFound %q", input.AppName))
 				return nil
 			}
+
+			// NOTE: Applications can always have storage. However, they
+			// will not be listed right after the application is created. So
+			// we need to wait for the storage to be ready. And we need to
+			// check if all storage constraints have pool equal "" and size equal 0
+			// to drop the error.
+			for _, storage := range output.Storage {
+				if storage.Pool == "" || storage.Size == 0 {
+					return fmt.Errorf("ReadApplicationWithRetryOnNotFound: no storage found in output")
+				}
+			}
+
 			// NOTE: An IAAS subordinate should also have machines. However, they
 			// will not be listed until after the relation has been created.
 			// Those happen with the integration resource which will not be
@@ -779,17 +791,6 @@ func (c applicationsClient) ReadApplicationWithRetryOnNotFound(ctx context.Conte
 				return fmt.Errorf("ReadApplicationWithRetryOnNotFound: need %d machines, have %d", output.Units, len(machines))
 			}
 
-			// NOTE: Applications can always have storage. However, they
-			// will not be listed right after the application is created. So
-			// we need to wait for the storage to be ready. And we need to
-			// check if all storage constraints have pool equal "" and size equal 0
-			// to drop the error.
-			for _, storage := range output.Storage {
-				if storage.Pool == "" || storage.Size == 0 {
-					return fmt.Errorf("ReadApplicationWithRetryOnNotFound: no storage found in output")
-				}
-			}
-
 			// NOTE: An IAAS subordinate should also have machines. However, they
 			// will not be listed until after the relation has been created.
 			// Those happen with the integration resource which will not be
@@ -899,7 +900,9 @@ func (c applicationsClient) ReadApplication(input *ReadApplicationInput) (*ReadA
 		IncludeStorage: true,
 	})
 	if err != nil {
-		if strings.Contains(err.Error(), "filesystem for storage instance") || strings.Contains(err.Error(), "volume for storage instance") {
+		if strings.Contains(err.Error(), "filesystem for storage instance") ||
+			strings.Contains(err.Error(), "volume for storage instance") ||
+			strings.Contains(err.Error(), "cannot convert storage details") {
 			// Retry if we get this error. It means the storage is not ready yet.
 			return nil, &storageNotFoundError{input.AppName}
 		}

internal/provider/resource_application_test.go

@@ -575,7 +575,7 @@ func TestAcc_ResourceApplication_UpdateEndpointBindings(t *testing.T) {
 	})
 }
 
-func TestAcc_ResourceApplication_Storage(t *testing.T) {
+func TestAcc_ResourceApplication_StorageLXD(t *testing.T) {
 	if testingCloud != LXDCloudTesting {
 		t.Skip(t.Name() + " only runs with LXD")
 	}
@@ -589,7 +589,7 @@ func TestAcc_ResourceApplication_Storage(t *testing.T) {
 		ProtoV6ProviderFactories: frameworkProviderFactories,
 		Steps: []resource.TestStep{
 			{
-				Config: testAccResourceApplicationStorage(modelName, appName, storageConstraints),
+				Config: testAccResourceApplicationStorageLXD(modelName, appName, storageConstraints),
 				Check: resource.ComposeTestCheckFunc(
 					resource.TestCheckResourceAttr("juju_application."+appName, "model", modelName),
 					resource.TestCheckResourceAttr("juju_application."+appName, "storage_directives.runner", "2G"),
@@ -603,6 +603,34 @@ func TestAcc_ResourceApplication_Storage(t *testing.T) {
 	})
 }
 
+func TestAcc_ResourceApplication_StorageK8s(t *testing.T) {
+	if testingCloud != MicroK8sTesting {
+		t.Skip(t.Name() + " only runs with Microk8s")
+	}
+	modelName := acctest.RandomWithPrefix("tf-test-application-storage")
+	appName := "test-app-storage"
+
+	storageConstraints := map[string]string{"label": "pgdata", "size": "2G"}
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:                 func() { testAccPreCheck(t) },
+		ProtoV6ProviderFactories: frameworkProviderFactories,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccResourceApplicationStorageK8s(modelName, appName, storageConstraints),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr("juju_application."+appName, "model", modelName),
+					resource.TestCheckResourceAttr("juju_application."+appName, "storage_directives.pgdata", "2G"),
+					resource.TestCheckResourceAttr("juju_application."+appName, "storage.0.label", "pgdata"),
+					resource.TestCheckResourceAttr("juju_application."+appName, "storage.0.count", "1"),
+					resource.TestCheckResourceAttr("juju_application."+appName, "storage.0.size", "2G"),
+					resource.TestCheckResourceAttr("juju_application."+appName, "storage.0.pool", "kubernetes"),
+				),
+			},
+		},
+	})
+}
+
 func testAccResourceApplicationBasic_Minimal(modelName, charmName string) string {
 	return fmt.Sprintf(`
 		resource "juju_model" "testmodel" {
@@ -950,7 +978,7 @@ resource "juju_application" "{{.AppName}}" {
 	})
 }
 
-func testAccResourceApplicationStorage(modelName, appName string, storageConstraints map[string]string) string {
+func testAccResourceApplicationStorageLXD(modelName, appName string, storageConstraints map[string]string) string {
 	return internaltesting.GetStringFromTemplateWithData("testAccResourceApplicationStorage", `
 resource "juju_model" "{{.ModelName}}" {
   name = "{{.ModelName}}"
@@ -978,6 +1006,33 @@ resource "juju_application" "{{.AppName}}" {
 	})
 }
 
+func testAccResourceApplicationStorageK8s(modelName, appName string, storageConstraints map[string]string) string {
+	return internaltesting.GetStringFromTemplateWithData("testAccResourceApplicationStorage", `
+resource "juju_model" "{{.ModelName}}" {
+  name = "{{.ModelName}}"
+}
+
+resource "juju_application" "{{.AppName}}" {
+  model = juju_model.{{.ModelName}}.name
+  name = "{{.AppName}}"
+  charm {
+    name = "postgresql-k8s"
+    channel = "14/stable"
+  }
+
+  storage_directives = {
+    {{.StorageConstraints.label}} = "{{.StorageConstraints.size}}"
+  }
+
+  units = 1
+}
+`, internaltesting.TemplateData{
+		"ModelName":          modelName,
+		"AppName":            appName,
+		"StorageConstraints": storageConstraints,
+	})
+}
+
 func testCheckEndpointsAreSetToCorrectSpace(modelName, appName, defaultSpace string, configuredEndpoints map[string]string) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		conn, err := TestClient.Models.GetConnection(&modelName)