Filter empty length key diffs in Storage Account resource

config/storage/config.go

@@ -5,14 +5,51 @@
 package storage
 
 import (
+	"errors"
+
 	"github.com/crossplane/upjet/pkg/config"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 
 	"github.com/upbound/provider-azure/apis/rconfig"
 	"github.com/upbound/provider-azure/config/common"
 )
 
 // Configure configures storage group
-func Configure(p *config.Provider) {
+func Configure(p *config.Provider) { //nolint:gocyclo
+	p.AddResourceConfigurator("azurerm_storage_account", func(r *config.Resource) {
+		r.TerraformCustomDiff = func(diff *terraform.InstanceDiff, state *terraform.InstanceState, config *terraform.ResourceConfig) (*terraform.InstanceDiff, error) {
+			// skip diff customization on create
+			if state == nil || state.Empty() {
+				return diff, nil
+			}
+			if config == nil {
+				return nil, errors.New("resource config cannot be nil")
+			}
+			// skip no diff or destroy diffs
+			if diff == nil || diff.Empty() || diff.Destroy || diff.Attributes == nil {
+				return diff, nil
+			}
+
+			lengthDiffKeys := []string{
+				"blob_properties.#",
+				"share_properties.#",
+				"queue_properties.#",
+			}
+			for _, key := range lengthDiffKeys {
+				// Note(cem): We should consider filtering effectively-empty
+				// (Old = "" and New = "") length keys (`*.#` and `*.%`) in
+				// Upjet. Doing so _should be_ safe, but in case we are afraid
+				// to deploy at scale, we might tie the functionality to a
+				// resource configuration flag, as a precaution.
+				if diff.Attributes[key] != nil && diff.Attributes[key].Old == "" && diff.Attributes[key].New == "" {
+					delete(diff.Attributes, key)
+				}
+			}
+
+			return diff, nil
+		}
+	})
+
 	p.AddResourceConfigurator("azurerm_storage_blob", func(r *config.Resource) {
 		r.References["storage_account_name"] = config.Reference{
 			TerraformName: "azurerm_storage_account",

examples/storage/v1beta1/account.yaml

@@ -0,0 +1,44 @@
+# SPDX-FileCopyrightText: 2024 The Crossplane Authors <https://crossplane.io>
+#
+# SPDX-License-Identifier: CC0-1.0
+
+# Note that this resource is not _properly_ Uptestable, because Uptest
+# cannot generate a random string that conforms to Azure Storage
+# Account naming criteria:
+# https://learn.microsoft.com/en-us/azure/storage/common/storage-account-overview#storage-account-name
+#
+# Uptest should succeed, as long as the hardcoded `metadata.name`
+# below is available.
+
+apiVersion: storage.azure.upbound.io/v1beta1
+kind: Account
+metadata:
+  annotations:
+    meta.upbound.io/example-id: storage/v1beta1/account
+  labels:
+    testing.upbound.io/example-name: example-storage
+  name: examplesa539891
+spec:
+  forProvider:
+    accountReplicationType: LRS
+    accountTier: Standard
+    location: "West Europe"
+    resourceGroupNameSelector:
+      matchLabels:
+        testing.upbound.io/example-name: example-storage
+
+---
+
+apiVersion: azure.upbound.io/v1beta1
+kind: ResourceGroup
+metadata:
+  annotations:
+    meta.upbound.io/example-id: storage/v1beta1/account
+  labels:
+    testing.upbound.io/example-name: example-storage
+  name: example-storage-${Rand.RFC1123Subdomain}
+spec:
+  forProvider:
+    location: "West Europe"
+    tags:
+      provisioner: crossplane