From 91973aca23ff95aeb9e92067a3b40ab725c2196f Mon Sep 17 00:00:00 2001
From: Ludovico Magnocavallo <ludomagno@google.com>
Date: Sat, 24 Jan 2026 10:58:25 +0100
Subject: [PATCH] add support for custom periods in factory budgets (#3674)

---
 modules/billing-account/README.md             |  8 ++-
 modules/billing-account/budgets.tf            |  4 --
 modules/billing-account/factory.tf            |  6 +-
 .../examples/budget-factory.yaml              | 64 +++++++++++++++++++
 4 files changed, 75 insertions(+), 7 deletions(-)
 create mode 100644 tests/modules/billing_account/examples/budget-factory.yaml

diff --git a/modules/billing-account/README.md b/modules/billing-account/README.md
index 5f43ef3d4..a9d9788e5 100644
--- a/modules/billing-account/README.md
+++ b/modules/billing-account/README.md
@@ -247,7 +247,7 @@ module "billing-account" {
     budgets_data_path = "data/billing-budgets"
   }
 }
-# tftest modules=1 resources=2 files=test-1  inventory=budget-monitoring-channel.yaml
+# tftest modules=1 resources=2 files=test-1  inventory=budget-factory.yaml
 ```
 
 ```yaml
@@ -256,7 +256,11 @@ amount:
   units: 100
 filter:
   period:
-    calendar: MONTH
+    custom:
+      start_date:
+        day: 1
+        month: 1
+        year: 2026
   resource_ancestors:
   - folders/1234567890
 threshold_rules:
diff --git a/modules/billing-account/budgets.tf b/modules/billing-account/budgets.tf
index 9fab983c4..6e7324c79 100644
--- a/modules/billing-account/budgets.tf
+++ b/modules/billing-account/budgets.tf
@@ -54,10 +54,6 @@ resource "google_monitoring_notification_channel" "default" {
 #       condition     = local.factory_budgets == null
 #       error_message = yamlencode(local.factory_budgets)
 #     }
-#     precondition {
-#       condition     = local.factory_budgets == null
-#       error_message = yamlencode(local.ctx.project_sets)
-#     }
 #   }
 # }
 
diff --git a/modules/billing-account/factory.tf b/modules/billing-account/factory.tf
index 2092f1605..3ee896db6 100644
--- a/modules/billing-account/factory.tf
+++ b/modules/billing-account/factory.tf
@@ -44,7 +44,11 @@ locals {
             v.filter.credit_types_treatment
           )
         )
-        label              = try(v.filter.label, null)
+        label = try(v.filter.label, null)
+        period = try(v.filter.period, null) == null ? null : merge(
+          { calendar = null, end_date = null, start_date = null },
+          v.filter.period
+        )
         projects           = try(v.filter.projects, [])
         resource_ancestors = try(v.filter.resource_ancestors, [])
         services           = try(v.filter.services, null)
diff --git a/tests/modules/billing_account/examples/budget-factory.yaml b/tests/modules/billing_account/examples/budget-factory.yaml
new file mode 100644
index 000000000..84748e132
--- /dev/null
+++ b/tests/modules/billing_account/examples/budget-factory.yaml
@@ -0,0 +1,64 @@
+# Copyright 2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+values:
+  module.billing-account.google_billing_budget.default["folder-net-month-current-100"]:
+    all_updates_rule:
+    - disable_default_iam_recipients: true
+      pubsub_topic: null
+      schema_version: '1.0'
+    amount:
+    - last_period_amount: null
+      specified_amount:
+      - nanos: null
+        units: '100'
+    billing_account: 012345-ABCDEF-012345
+    budget_filter:
+    - credit_types_treatment: INCLUDE_ALL_CREDITS
+      custom_period:
+      - end_date: []
+        start_date:
+        - day: 1
+          month: 1
+          year: 2026
+      projects: null
+      resource_ancestors:
+      - folders/1234567890
+    display_name: 100 dollars in current spend
+    threshold_rules:
+    - spend_basis: CURRENT_SPEND
+      threshold_percent: 0.5
+    - spend_basis: CURRENT_SPEND
+      threshold_percent: 0.75
+    timeouts: null
+  module.billing-account.google_monitoring_notification_channel.default["billing-default"]:
+    description: null
+    display_name: Budget email notification billing-default.
+    enabled: true
+    force_delete: false
+    labels:
+      email_address: gcp-billing-admins@example.com
+    project: tf-playground-simple
+    sensitive_labels: []
+    timeouts: null
+    type: email
+    user_labels: null
+
+counts:
+  google_billing_budget: 1
+  google_monitoring_notification_channel: 1
+  modules: 1
+  resources: 2
+
+outputs: {}