refactor(extensions): use declare function pattern for colors bridge

Replace the registry-with-state implementation in @apache-superset/core/colors
with declare-only function signatures. The host app (ExtensionsStartup) now
provides the concrete implementations via window.superset.colors, matching
the same pattern used by the authentication module.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

superset-frontend/packages/superset-core/src/colors/colors.test.ts

@@ -17,13 +17,7 @@
  * under the License.
  */
 
-import {
-  ColorSchemeGroup,
-  getCategoricalSchemeNames,
-  getCategoricalSchemeRegistry,
-  getSchemeColors,
-  registerCategoricalSchemeRegistry,
-} from '@apache-superset/core/colors';
+import { ColorSchemeGroup } from '@apache-superset/core/colors';
 
 // ─── ColorSchemeGroup enum ────────────────────────────────────────────────────
 
@@ -32,35 +26,3 @@ test('ColorSchemeGroup has the expected string values', () => {
   expect(ColorSchemeGroup.Featured).toBe('featured');
   expect(ColorSchemeGroup.Other).toBe('other');
 });
-
-// ─── Registry bridge ─────────────────────────────────────────────────────────
-
-test('getCategoricalSchemeNames returns [] before any registry is injected', () => {
-  registerCategoricalSchemeRegistry({ keys: () => [], get: () => null });
-  expect(getCategoricalSchemeNames()).toEqual([]);
-});
-
-test('getCategoricalSchemeNames returns alphabetically sorted names', () => {
-  registerCategoricalSchemeRegistry({
-    keys: () => ['zebra', 'apple', 'mango'],
-    get: () => null,
-  });
-  expect(getCategoricalSchemeNames()).toEqual(['apple', 'mango', 'zebra']);
-});
-
-test('getSchemeColors returns the color array for a known scheme', () => {
-  const colors = ['#ff0000', '#00ff00', '#0000ff'];
-  registerCategoricalSchemeRegistry({
-    keys: () => ['testScheme'],
-    get: (name: string) =>
-      name === 'testScheme' ? { id: 'testScheme', colors } : null,
-  });
-  expect(getSchemeColors('testScheme')).toEqual(colors);
-  expect(getSchemeColors('nonexistent')).toBeNull();
-});
-
-test('getCategoricalSchemeRegistry returns the injected registry object', () => {
-  const mockRegistry = { keys: () => ['a', 'b'], get: () => null };
-  registerCategoricalSchemeRegistry(mockRegistry);
-  expect(getCategoricalSchemeRegistry()).toBe(mockRegistry);
-});

superset-frontend/packages/superset-core/src/colors/index.ts

@@ -21,13 +21,6 @@
 export type { ColorSchemeConfig, SequentialSchemeConfig } from './types';
 export { ColorSchemeGroup } from './types';
 
-// ─── Registry bridge for extensions ──────────────────────────────────────────
-//
-// The host app (ExtensionsStartup) calls `registerCategoricalSchemeRegistry()`
-// to inject @superset-ui/core's live singleton.  Extensions then call
-// `getCategoricalSchemeNames()` / `getSchemeColors()` and receive the same
-// palettes that the host app registered (including any custom extra schemes).
-
 /**
  * Minimal interface for the categorical color scheme registry.
  * Mirrors the public surface of @superset-ui/core's ColorSchemeRegistry.
@@ -43,37 +36,16 @@ export interface CategoricalSchemeRegistryLike {
   get(name: string): CategoricalScheme | null | undefined;
 }
 
-let _registry: CategoricalSchemeRegistryLike | null = null;
-
 /**
- * Called by the Superset host app (ExtensionsStartup) to inject the
- * categorical color scheme registry so extensions can access it without
- * depending directly on @superset-ui/core.
+ * Returns an alphabetically sorted list of all registered categorical color
+ * scheme names. The host app (ExtensionsStartup) provides the implementation
+ * via window.superset.colors.
  */
-export function registerCategoricalSchemeRegistry(
-  registry: CategoricalSchemeRegistryLike,
-): void {
-  _registry = registry;
-}
-
-/**
- * Returns the categorical color scheme registry registered by the host app,
- * or null if not yet injected (e.g. in tests or isolated builds).
- */
-export function getCategoricalSchemeRegistry(): CategoricalSchemeRegistryLike | null {
-  return _registry;
-}
-
-/**
- * Returns an alphabetically sorted list of all registered scheme names.
- */
-export function getCategoricalSchemeNames(): string[] {
-  return _registry?.keys().sort() ?? [];
-}
+export declare function getCategoricalSchemeNames(): string[];
 
 /**
  * Returns the color array for a named scheme, or null if not found.
+ * The host app (ExtensionsStartup) provides the implementation
+ * via window.superset.colors.
  */
-export function getSchemeColors(schemeName: string): string[] | null {
-  return _registry?.get(schemeName)?.colors ?? null;
-}
+export declare function getSchemeColors(schemeName: string): string[] | null;

superset-frontend/src/extensions/ExtensionsStartup.tsx

@@ -24,6 +24,7 @@ import {
   isFeatureEnabled,
   getCategoricalSchemeRegistry,
 } from '@superset-ui/core';
+import type { CategoricalSchemeRegistryLike } from '@apache-superset/core/colors';
 import {
   authentication,
   core,
@@ -49,7 +50,11 @@ declare global {
       menus: typeof menus;
       sqlLab: typeof sqlLab;
       views: typeof views;
-      colors: typeof supersetCore.colors;
+      colors: {
+        ColorSchemeGroup: typeof supersetCore.colors.ColorSchemeGroup;
+        getCategoricalSchemeNames(): string[];
+        getSchemeColors(schemeName: string): string[] | null;
+      };
     };
   }
 }
@@ -73,6 +78,8 @@ const ExtensionsStartup: React.FC<{ children?: React.ReactNode }> = ({
     }
 
     // Provide the implementations for @apache-superset/core
+    const registry =
+      getCategoricalSchemeRegistry() as CategoricalSchemeRegistryLike | null;
     window.superset = {
       ...supersetCore,
       authentication,
@@ -83,14 +90,17 @@ const ExtensionsStartup: React.FC<{ children?: React.ReactNode }> = ({
       menus,
       sqlLab,
       views,
+      colors: {
+        ColorSchemeGroup: supersetCore.colors.ColorSchemeGroup,
+        getCategoricalSchemeNames(): string[] {
+          return (registry?.keys() ?? []).sort();
+        },
+        getSchemeColors(schemeName: string): string[] | null {
+          return registry?.get(schemeName)?.colors ?? null;
+        },
+      },
     };
 
-    // Inject the categorical color scheme registry so extensions can access
-    // Superset's registered palettes without depending on @superset-ui/core.
-    supersetCore.colors.registerCategoricalSchemeRegistry(
-      getCategoricalSchemeRegistry(),
-    );
-
     const setup = async () => {
       if (isFeatureEnabled(FeatureFlag.EnableExtensions)) {
         try {