[feat] Add reactive feature flags foundation (#4817)

src/composables/useFeatureFlags.ts

@@ -0,0 +1,36 @@
+import { computed, reactive, readonly } from 'vue'
+
+import { api } from '@/scripts/api'
+
+/**
+ * Known server feature flags (top-level, not extensions)
+ */
+export enum ServerFeatureFlag {
+  SUPPORTS_PREVIEW_METADATA = 'supports_preview_metadata',
+  MAX_UPLOAD_SIZE = 'max_upload_size'
+}
+
+/**
+ * Composable for reactive access to feature flags
+ */
+export function useFeatureFlags() {
+  // Create reactive state that tracks server feature flags
+  const flags = reactive({
+    get supportsPreviewMetadata() {
+      return api.getServerFeature(ServerFeatureFlag.SUPPORTS_PREVIEW_METADATA)
+    },
+    get maxUploadSize() {
+      return api.getServerFeature(ServerFeatureFlag.MAX_UPLOAD_SIZE)
+    }
+  })
+
+  // Create a reactive computed for any feature flag
+  const featureFlag = <T = unknown>(featurePath: string, defaultValue?: T) => {
+    return computed(() => api.getServerFeature(featurePath, defaultValue))
+  }
+
+  return {
+    flags: readonly(flags),
+    featureFlag
+  }
+}

src/scripts/api.ts

@@ -1,4 +1,5 @@
 import axios from 'axios'
+import get from 'lodash/get'
 
 import defaultClientFeatureFlags from '@/config/clientFeatureFlags.json'
 import type {
@@ -1082,21 +1083,21 @@ export class ComfyApi extends EventTarget {
 
   /**
    * Checks if the server supports a specific feature.
-   * @param featureName The name of the feature to check
+   * @param featureName The name of the feature to check (supports dot notation for nested values)
    * @returns true if the feature is supported, false otherwise
    */
   serverSupportsFeature(featureName: string): boolean {
-    return this.serverFeatureFlags[featureName] === true
+    return get(this.serverFeatureFlags, featureName) === true
   }
 
   /**
    * Gets a server feature flag value.
-   * @param featureName The name of the feature to get
+   * @param featureName The name of the feature to get (supports dot notation for nested values)
    * @param defaultValue The default value if the feature is not found
    * @returns The feature value or default
    */
   getServerFeature<T = unknown>(featureName: string, defaultValue?: T): T {
-    return (this.serverFeatureFlags[featureName] ?? defaultValue) as T
+    return get(this.serverFeatureFlags, featureName, defaultValue) as T
   }
 
   /**