fix discriminated union not working in update operation

Author: tylim88

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "firelord",
-	"version": "2.6.27",
+	"version": "2.6.28",
 	"description": "🔥 Write V9 like Firestore Admin code with extreme type safety.",
 	"author": "tylim",
 	"license": "MIT",

src/types/exactOptional.test.ts

@@ -7,6 +7,35 @@ import { IsTrue, IsSame } from './utils'
 import { ServerTimestamp } from './fieldValues'
 
 describe('test exact optional', () => {
+	it('test discriminated union', () => {
+		IsTrue<
+			IsSame<
+				ExactOptional<
+					{ a: { b: 0; d: 1 } | { b: 1; c: 2 } },
+					{ a: { b: 0; d: 1 } },
+					false,
+					false,
+					true
+				>,
+				{
+					a?:
+						| { b?: 0; d?: 1 }
+						| HandleUnknownMember<
+								// TODO remove this extra type
+								{
+									b: 1
+									c: 2
+								},
+								{
+									b: 0
+									d: 1
+								}
+						  >
+				}
+			>
+		>()
+	})
+
 	it('test union of primitive type with oject literal', () => {
 		IsTrue<
 			IsSame<
@@ -141,6 +170,30 @@ describe('test exact optional', () => {
 })
 
 describe('test RecursivelyReplaceDeleteFieldWithErrorMsg', () => {
+	it('test discriminated union', () => {
+		IsTrue<
+			IsSame<
+				RecursivelyReplaceDeleteFieldWithErrorMsg<
+					{ a: { b: 0; d: 1 } | { b: 1; c: 2 } },
+					{ a: { b: 0; d: 1 } }
+				>,
+				{
+					a:
+						| { b: 0; d: 1 }
+						| HandleUnknownMember<
+								{
+									b: 1
+									c: 2
+								},
+								{
+									b: 0
+									d: 1
+								}
+						  >
+				}
+			>
+		>()
+	})
 	it('test union of primitive type with oject literal', () => {
 		IsTrue<
 			IsSame<

src/types/exactOptional.ts

@@ -67,13 +67,15 @@ export type ExactOptional<
 	Merge extends boolean | string[], // this is for set merge operation only
 	NoFlatten extends boolean,
 	TopLevel extends boolean
-> = Data extends (
-	NoFlatten extends true
-		? TopLevel extends true
-			? Record<string, never>
-			: never
-		: Record<string, never>
-)
+> = T extends never
+	? T
+	: Data extends (
+			NoFlatten extends true
+				? TopLevel extends true
+					? Record<string, never>
+					: never
+				: Record<string, never>
+	  )
 	? ErrorEmptyUpdate | T
 	: keyof Data extends (string extends keyof T ? string | number : keyof T)
 	? {