chore: add useModelMigration composable

Signed-off-by: Grigorii K. Shartsev <[email protected]>

src/composables/useModelMigration.ts

@@ -0,0 +1,32 @@
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { getCurrentInstance, computed } from 'vue'
+
+/**
+ * Create model proxy to new v9 model (modelValue + update:modelValue) with a fallback to old model
+ * @param {string} oldModelName - Name of model prop in nextcloud-vue v8
+ * @param {string} oldModelEvent - Event name of model event in nextcloud-vue v8
+ * @return {import('vue').WritableComputedRef} - model proxy
+ */
+export function useModelMigration(oldModelName, oldModelEvent) {
+    const vm = getCurrentInstance()!.proxy
+
+    const model = computed({
+        get() {
+            if (vm.$props[oldModelName] !== undefined) {
+                return vm.$props[oldModelName]
+            }
+            return vm.$props.modelValue
+        },
+
+        set(value) {
+            vm.$emit('update:modelValue', value)
+            vm.$emit(oldModelEvent, value)
+        }
+    })
+
+    return model
+}