fix

internal/services/elasticsan/elastic_san_resource.go

@@ -160,11 +160,11 @@ func (k ElasticSANResource) CustomizeDiff() sdk.ResourceFunc {
 			}
 
 			if oldVal, newVal := metadata.ResourceDiff.GetChange("base_size_in_tib"); newVal.(int) < oldVal.(int) {
-				return fmt.Errorf("base_size_in_tib cannot be reduced")
+				return fmt.Errorf("new base_size_in_tib should be greater than the existing one")
 			}
 
 			if oldVal, newVal := metadata.ResourceDiff.GetChange("extended_size_in_tib"); newVal.(int) < oldVal.(int) {
-				return fmt.Errorf("extended_size_in_tib cannot be reduced")
+				return fmt.Errorf("new extended_size_in_tib should be greater than the existing one")
 			}
 
 			return nil

internal/services/elasticsan/elastic_san_resource_test.go

@@ -100,6 +100,35 @@ func TestAccElasticSAN_update(t *testing.T) {
 	})
 }
 
+func TestAccElasticSAN_updateTags(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_elastic_san", "test")
+	r := ElasticSANTestResource{}
+
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.basic(data),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+		{
+			Config: r.basicWithTags(data),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+		{
+			Config: r.basic(data),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+	})
+}
+
 func TestAccElasticSAN_reduceBaseSize(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_elastic_san", "test")
 	r := ElasticSANTestResource{}
@@ -154,6 +183,29 @@ resource "azurerm_elastic_san" "test" {
 `, r.template(data))
 }
 
+func (r ElasticSANTestResource) basicWithTags(data acceptance.TestData) string {
+	return fmt.Sprintf(`
+%s
+
+provider "azurerm" {
+  features {}
+}
+
+resource "azurerm_elastic_san" "test" {
+  name                = "acctestes-${var.random_string}"
+  resource_group_name = azurerm_resource_group.test.name
+  location            = azurerm_resource_group.test.location
+  base_size_in_tib    = 1
+  sku {
+    name = "Premium_LRS"
+  }
+  tags = {
+    foo = "bar"
+  }
+}
+`, r.template(data))
+}
+
 func (r ElasticSANTestResource) zoneWithZRS(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 %s

website/docs/r/elastic_san.html.markdown

@@ -41,12 +41,14 @@ The following arguments are supported:
 
 * `base_size_in_tib` - (Required) Specifies the base size of the Elastic SAN resource in TiB. Possible values are between `1` and `100`.
 
-* `extended_size_in_tib` - (Required) Specifies the extended size of the Elastic SAN resource in TiB. Possible values are between `1` and `100`.
-
--> **NOTE** `base_size_in_tib` and `extended_size_in_tib` cannot be reduced.
+-> **NOTE** When updating `base_size_in_tib`, the new value should be greater than the existing one.
 
 * `sku` - (Required) A `sku` block as defined below.
 
+* `extended_size_in_tib` - (Optional) Specifies the extended size of the Elastic SAN resource in TiB. Possible values are between `1` and `100`.
+
+-> **NOTE** `extended_size_in_tib` cannot be removed and when updating, the new value should be greater than the existing one.
+
 * `zones` - (Optional) Logical zone for the Elastic SAN resource. Changing this forces a new resource to be created.
 
 -> **NOTE** `zones` cannot be specified if `sku.name` is set to `Premium_ZRS`.