fix: restrict in-page listeners to events

Author: posva

packages/devframe/src/in-page-channel/types.test-d.ts

@@ -21,6 +21,14 @@ interface PageScriptOnlyProtocol {
   panel: Record<string, never>
 }
 
+interface MixedPanelProtocol {
+  pageScript: Record<string, never>
+  panel: {
+    confirm: (message: string) => boolean
+    notify: (message: string) => void
+  }
+}
+
 describe('Channel function definitions', () => {
   it('distinguishes event, query, and action definitions', () => {
     defineChannelFunction({ name: 'notify', type: 'event' })
@@ -177,16 +185,18 @@ describe('In-page script channel', () => {
   })
 
   describe('Event checking', () => {
-    it('types runtime subscriptions to page-script functions', () => {
-      const unsubscribe = channel.on('echo', (value) => {
+    it('types runtime subscriptions to page-script events', () => {
+      const unsubscribe = channel.on('save', (value) => {
         expectTypeOf(value).toEqualTypeOf<string>()
       })
 
       expectTypeOf(unsubscribe).toEqualTypeOf<() => void>()
       // @ts-expect-error Panel functions cannot be handled by the page script.
       channel.on('notify', () => {})
-      // @ts-expect-error `echo` listeners receive a string.
-      channel.on('echo', (value: number) => void value)
+      // @ts-expect-error Query functions cannot be handled as events.
+      channel.on('echo', () => {})
+      // @ts-expect-error `save` listeners receive a string.
+      channel.on('save', (value: number) => void value)
     })
 
     it('types panel connection events', () => {
@@ -353,6 +363,20 @@ describe('Panel channel', () => {
       channel.on('notify', (message: number) => void message)
     })
 
+    it('rejects runtime subscriptions to panel queries', () => {
+      const mixedChannel = connectPanelChannel<MixedPanelProtocol>({
+        name: 'devframes:mixed-panel',
+        functions: {
+          confirm: { handler: () => true },
+          notify: { type: 'event' },
+        },
+      })
+
+      mixedChannel.on('notify', () => {})
+      // @ts-expect-error Query functions cannot be handled as events.
+      mixedChannel.on('confirm', () => {})
+    })
+
     it('types status events', () => {
       const unsubscribe = channel.events.on('status:updated', (status) => {
         expectTypeOf(status).toEqualTypeOf<'connecting' | 'connected' | 'closed'>()

packages/devframe/src/in-page-channel/types.ts

@@ -31,6 +31,22 @@ type SharedStates<P extends InPageChannelProtocol>
 type FnArgs<F> = F extends (...args: infer A) => any ? A : never
 type FnReturn<F> = F extends (...args: any[]) => infer R ? Awaited<R> : never
 
+/**
+ * Page-script functions whose resolved return type marks an event.
+ * @internal
+ */
+type PageScriptFunctionsEvents<P extends InPageChannelProtocol> = {
+  [K in keyof PageScriptFunctions<P> as FnReturn<PageScriptFunctions<P>[K]> extends void ? K : never]: PageScriptFunctions<P>[K]
+}
+
+/**
+ * Panel functions whose resolved return type marks an event.
+ * @internal
+ */
+type PanelFunctionsEvents<P extends InPageChannelProtocol> = {
+  [K in keyof PanelFunctions<P> as FnReturn<PanelFunctions<P>[K]> extends void ? K : never]: PanelFunctions<P>[K]
+}
+
 /**
  * Converts a protocol function to its accepted endpoint handler.
  *
@@ -340,9 +356,9 @@ export interface PageScriptChannel<P extends InPageChannelProtocol> {
     ...args: FnArgs<PanelFunctions<P>[K]>
   ) => void
   /** Subscribe to an event emitted by a panel. Returns an unsubscribe function. */
-  on: <K extends keyof PageScriptFunctions<P> & string>(
+  on: <K extends keyof PageScriptFunctionsEvents<P> & string>(
     name: K,
-    listener: (...args: FnArgs<PageScriptFunctions<P>[K]>) => void,
+    listener: (...args: FnArgs<PageScriptFunctionsEvents<P>[K]>) => void,
   ) => () => void
   /** Page-script-authoritative shared states, replayed to joining panels. */
   readonly sharedState: InPageSharedStateHost<P>
@@ -397,9 +413,9 @@ export interface PanelChannel<P extends InPageChannelProtocol> {
     ...args: FnArgs<PageScriptFunctions<P>[K]>
   ) => void
   /** Subscribe to an event emitted by the page script. Returns an unsubscribe function. */
-  on: <K extends keyof PanelFunctions<P> & string>(
+  on: <K extends keyof PanelFunctionsEvents<P> & string>(
     name: K,
-    listener: (...args: FnArgs<PanelFunctions<P>[K]>) => void,
+    listener: (...args: FnArgs<PanelFunctionsEvents<P>[K]>) => void,
   ) => () => void
   /** Shared states mirrored from the page-script authority. */
   readonly sharedState: InPageSharedStateHost<P>

tests/__snapshots__/tsnapi/devframe/in-page-channel.snapshot.d.ts

@@ -27,7 +27,7 @@ export interface PageScriptChannel<P extends InPageChannelProtocol> {
   readonly events: Pick<EventEmitter<PageScriptChannelEvents<P>>, 'on' | 'once'>;
   emit: <K extends keyof PanelFunctions<P> & string>(_: K, ..._: FnArgs<PanelFunctions<P>[K]>) => void;
   callEvent: <K extends keyof PanelFunctions<P> & string>(_: K, ..._: FnArgs<PanelFunctions<P>[K]>) => void;
-  on: <K extends keyof PageScriptFunctions<P> & string>(_: K, _: (..._: FnArgs<PageScriptFunctions<P>[K]>) => void) => () => void;
+  on: <K extends keyof PageScriptFunctionsEvents<P> & string>(_: K, _: (..._: FnArgs<PageScriptFunctionsEvents<P>[K]>) => void) => () => void;
   readonly sharedState: InPageSharedStateHost<P>;
   addPanelPort: (_: MessagePort) => PanelPeer<P>;
   close: () => void;
@@ -43,7 +43,7 @@ export interface PanelChannel<P extends InPageChannelProtocol> {
   call: <K extends keyof PageScriptFunctions<P> & string>(_: K, ..._: FnArgs<PageScriptFunctions<P>[K]>) => Promise<FnReturn<PageScriptFunctions<P>[K]>>;
   emit: <K extends keyof PageScriptFunctions<P> & string>(_: K, ..._: FnArgs<PageScriptFunctions<P>[K]>) => void;
   callEvent: <K extends keyof PageScriptFunctions<P> & string>(_: K, ..._: FnArgs<PageScriptFunctions<P>[K]>) => void;
-  on: <K extends keyof PanelFunctions<P> & string>(_: K, _: (..._: FnArgs<PanelFunctions<P>[K]>) => void) => () => void;
+  on: <K extends keyof PanelFunctionsEvents<P> & string>(_: K, _: (..._: FnArgs<PanelFunctionsEvents<P>[K]>) => void) => () => void;
   readonly sharedState: InPageSharedStateHost<P>;
   close: () => void;
 }
@@ -117,8 +117,10 @@ interface PageScriptChannelEvents<P extends InPageChannelProtocol> {
   'panel:disconnected': (_: PanelPeer<P>) => void;
 }
 type PageScriptFunctions<P extends InPageChannelProtocol> = SideFunctions<NonNullable<P['pageScript']>>;
+type PageScriptFunctionsEvents<P extends InPageChannelProtocol> = { [K in keyof PageScriptFunctions<P> as FnReturn<PageScriptFunctions<P>[K]> extends void ? K : never]: PageScriptFunctions<P>[K]; };
 interface PanelChannelEvents {
   'status:updated': (_: InPageChannelStatus) => void;
 }
 type PanelFunctions<P extends InPageChannelProtocol> = SideFunctions<NonNullable<P['panel']>>;
+type PanelFunctionsEvents<P extends InPageChannelProtocol> = { [K in keyof PanelFunctions<P> as FnReturn<PanelFunctions<P>[K]> extends void ? K : never]: PanelFunctions<P>[K]; };
 // #endregion