refactor(provider): enhance provider type inference and streamline exports

Author: braden-w

apps/tab-manager/src/lib/epicenter/background.workspace.ts

@@ -342,15 +342,6 @@ export const backgroundWorkspace = defineWorkspace({
 		},
 	},
 	exports: ({ tables, providers }) => {
-		// Type assertions for provider exports
-		// TypeScript can't infer these through the generic chain
-		const persistence = providers.persistence as {
-			whenSynced: Promise<IndexeddbPersistence>;
-		};
-		const chromeSync = providers.chromeSync as {
-			syncAllFromChrome: () => Promise<void>;
-		};
-
 		return {
 			/**
 			 * Get the tables for direct access.
@@ -361,14 +352,14 @@ export const backgroundWorkspace = defineWorkspace({
 			 * Wait for IndexedDB to finish initial sync.
 			 */
 			get whenSynced() {
-				return persistence.whenSynced;
+				return providers.persistence.whenSynced;
 			},
 
 			/**
 			 * Perform a full sync from Chrome to Y.Doc.
 			 * Clears existing data and re-syncs all tabs/windows.
 			 */
-			syncAllFromChrome: chromeSync.syncAllFromChrome,
+			syncAllFromChrome: providers.chromeSync.syncAllFromChrome,
 
 			/**
 			 * Get all tabs sorted by index.

packages/epicenter/src/core/provider.ts

@@ -123,6 +123,31 @@ export type Provider<
  */
 export type WorkspaceProviderMap = Record<string, ProviderExports>;
 
+/**
+ * Infer the exports type from a provider function.
+ *
+ * Extracts the return type from a provider, unwrapping Promise and excluding void.
+ * Returns `Record<string, never>` (empty object) for providers that return void.
+ *
+ * @example
+ * ```typescript
+ * // Provider that returns exports
+ * const myProvider = ({ ydoc }) => defineProviderExports({ db: sqlite });
+ * type Exports = InferProviderExports<typeof myProvider>;
+ * // Exports = { db: typeof sqlite }
+ *
+ * // Provider that returns void (side effects only)
+ * const sideEffectProvider = ({ ydoc }) => { ydoc.on('update', ...); };
+ * type Exports = InferProviderExports<typeof sideEffectProvider>;
+ * // Exports = Record<string, never>
+ * ```
+ */
+export type InferProviderExports<P> = P extends (context: any) => infer R
+	? Awaited<R> extends void | undefined
+		? Record<string, never>
+		: Exclude<Awaited<R>, void | undefined>
+	: Record<string, never>;
+
 /**
  * Define provider exports with type safety (identity function).
  *

packages/epicenter/src/core/workspace/client.browser.ts

@@ -12,7 +12,7 @@
 import * as Y from 'yjs';
 import type { WorkspaceActionMap, WorkspaceExports } from '../actions';
 import { createEpicenterDb } from '../db/core';
-import type { ProviderExports, WorkspaceProviderMap } from '../provider';
+import type { Provider, ProviderExports } from '../provider';
 import type { WorkspaceSchema } from '../schema';
 import { createWorkspaceValidators } from '../schema';
 import type { WorkspaceClient, WorkspacesToClients } from './client.shared';
@@ -396,16 +396,10 @@ export function createWorkspaceClient<
 	const TDeps extends readonly AnyWorkspaceConfig[],
 	const TId extends string,
 	TWorkspaceSchema extends WorkspaceSchema,
-	const TProviderResults extends WorkspaceProviderMap,
+	const TProviders extends Record<string, Provider<TWorkspaceSchema>>,
 	TExports extends WorkspaceExports,
 >(
-	workspace: WorkspaceConfig<
-		TDeps,
-		TId,
-		TWorkspaceSchema,
-		TProviderResults,
-		TExports
-	>,
+	workspace: WorkspaceConfig<TDeps, TId, TWorkspaceSchema, TProviders, TExports>,
 ): WorkspaceClient<TExports> {
 	// Collect all workspace configs (target + dependencies) for flat/hoisted initialization
 	const allWorkspaceConfigs: WorkspaceConfig[] = [];

packages/epicenter/src/core/workspace/client.node.ts

@@ -12,7 +12,7 @@ import path from 'node:path';
 import * as Y from 'yjs';
 import type { WorkspaceActionMap, WorkspaceExports } from '../actions';
 import { createEpicenterDb } from '../db/core';
-import type { ProviderExports, WorkspaceProviderMap } from '../provider';
+import type { Provider, ProviderExports } from '../provider';
 import type { WorkspaceSchema } from '../schema';
 import { createWorkspaceValidators } from '../schema';
 import type { EpicenterDir, StorageDir } from '../types';
@@ -395,16 +395,10 @@ export async function createWorkspaceClient<
 	const TDeps extends readonly AnyWorkspaceConfig[],
 	const TId extends string,
 	TWorkspaceSchema extends WorkspaceSchema,
-	const TProviderResults extends WorkspaceProviderMap,
+	const TProviders extends Record<string, Provider<TWorkspaceSchema>>,
 	TExports extends WorkspaceExports,
 >(
-	workspace: WorkspaceConfig<
-		TDeps,
-		TId,
-		TWorkspaceSchema,
-		TProviderResults,
-		TExports
-	>,
+	workspace: WorkspaceConfig<TDeps, TId, TWorkspaceSchema, TProviders, TExports>,
 ): Promise<WorkspaceClient<TExports>> {
 	// Collect all workspace configs (target + dependencies) for flat/hoisted initialization
 	const allWorkspaceConfigs: WorkspaceConfig[] = [];

packages/epicenter/src/core/workspace/config.ts

@@ -1,11 +1,7 @@
 import type { WorkspaceExports } from '../actions';
 import type { WorkspaceBlobs } from '../blobs';
 import type { Tables } from '../db/core';
-import type {
-	Provider,
-	ProviderExports,
-	WorkspaceProviderMap,
-} from '../provider';
+import type { InferProviderExports, Provider } from '../provider';
 import type { WorkspaceSchema, WorkspaceValidators } from '../schema';
 import type { EpicenterDir, StorageDir } from '../types';
 
@@ -103,17 +99,11 @@ export function defineWorkspace<
 	const TDeps extends readonly AnyWorkspaceConfig[],
 	const TId extends string,
 	TWorkspaceSchema extends WorkspaceSchema,
-	const TProviderResults extends WorkspaceProviderMap,
+	const TProviders extends Record<string, Provider<TWorkspaceSchema>>,
 	TExports extends WorkspaceExports,
 >(
-	workspace: WorkspaceConfig<
-		TDeps,
-		TId,
-		TWorkspaceSchema,
-		TProviderResults,
-		TExports
-	>,
-): WorkspaceConfig<TDeps, TId, TWorkspaceSchema, TProviderResults, TExports> {
+	workspace: WorkspaceConfig<TDeps, TId, TWorkspaceSchema, TProviders, TExports>,
+): WorkspaceConfig<TDeps, TId, TWorkspaceSchema, TProviders, TExports> {
 	// Validate workspace ID
 	if (!workspace.id || typeof workspace.id !== 'string') {
 		throw new Error('Workspace must have a valid string ID');
@@ -142,6 +132,14 @@ export function defineWorkspace<
  *
  * Fully-featured workspace configuration used for defining workspaces and their dependencies.
  *
+ * ## Provider Type Inference
+ *
+ * The `TProviders` type parameter captures the actual provider functions you pass.
+ * The `exports` factory receives provider exports derived via `InferProviderExports`:
+ * - Provider returns `{ db: Db }` → exports receives `{ db: Db }`
+ * - Provider returns `void` → exports receives `Record<string, never>` (empty object)
+ * - Provider returns `Promise<{ db: Db }>` → exports receives `{ db: Db }` (unwrapped)
+ *
  * ## Dependency Constraint
  *
  * The `dependencies` field uses `AnyWorkspaceConfig[]` as a minimal constraint.
@@ -161,18 +159,16 @@ export type WorkspaceConfig<
 	TDeps extends readonly AnyWorkspaceConfig[] = readonly AnyWorkspaceConfig[],
 	TId extends string = string,
 	TWorkspaceSchema extends WorkspaceSchema = WorkspaceSchema,
-	TProviderResults extends WorkspaceProviderMap = WorkspaceProviderMap,
+	TProviders extends Record<string, Provider<TWorkspaceSchema>> = Record<
+		string,
+		Provider<TWorkspaceSchema>
+	>,
 	TExports extends WorkspaceExports = WorkspaceExports,
 > = {
 	id: TId;
 	tables: TWorkspaceSchema;
 	dependencies?: TDeps;
-	providers: {
-		[K in keyof TProviderResults]: Provider<
-			TWorkspaceSchema,
-			TProviderResults[K] extends ProviderExports ? TProviderResults[K] : ProviderExports
-		>;
-	};
+	providers: TProviders;
 	/**
 	 * Factory function that creates workspace exports (actions, utilities, etc.)
 	 *
@@ -213,7 +209,7 @@ export type WorkspaceConfig<
 		schema: TWorkspaceSchema;
 		validators: WorkspaceValidators<TWorkspaceSchema>;
 		workspaces: WorkspacesToExports<TDeps>;
-		providers: TProviderResults;
+		providers: { [K in keyof TProviders]: InferProviderExports<TProviders[K]> };
 		blobs: WorkspaceBlobs<TWorkspaceSchema>;
 		storageDir: StorageDir | undefined;
 		epicenterDir: EpicenterDir | undefined;

packages/epicenter/src/index.shared.ts

@@ -97,6 +97,7 @@ export {
 } from './core/errors';
 
 export type {
+	InferProviderExports,
 	Provider,
 	ProviderContext,
 	ProviderExports,