fix(serializer/types): Allow null value in serializer for parsers with default values

packages/nuqs/src/parsers.ts

@@ -421,13 +421,13 @@ export function parseAsArrayOf<ItemType>(
 }
 
 type inferSingleParserType<Parser> = Parser extends ParserBuilder<
-  infer Type
+  infer Value
 > & {
-  defaultValue: infer Type
+  defaultValue: infer Value
 }
-  ? Type
-  : Parser extends ParserBuilder<infer Type>
-    ? Type | null
+  ? Value
+  : Parser extends ParserBuilder<infer Value>
+    ? Value | null
     : never
 
 type inferParserRecordType<Map extends Record<string, ParserBuilder<any>>> = {

packages/nuqs/src/serializer.test.ts

@@ -86,6 +86,20 @@ describe('serializer', () => {
     const result = serialize('?str=foo&external=kept', null)
     expect(result).toBe('?external=kept')
   })
+  test('clears value when setting null for search param that has a default value', () => {
+    const serialize = createSerializer({
+      int: parseAsInteger.withDefault(0)
+    })
+    const result = serialize('?int=1&str=foo', { int: null })
+    expect(result).toBe('?str=foo')
+  })
+  test('clears value when setting null for search param that is set to its default value', () => {
+    const serialize = createSerializer({
+      int: parseAsInteger.withDefault(0)
+    })
+    const result = serialize('?int=0&str=foo', { int: null })
+    expect(result).toBe('?str=foo')
+  })
   test('clears value when setting the default value (`clearOnDefault: true` is the default)', () => {
     const serialize = createSerializer({
       int: parseAsInteger.withDefault(0),

packages/nuqs/src/serializer.ts

@@ -1,4 +1,4 @@
-import type { Options } from './defs'
+import type { Nullable, Options } from './defs'
 import type { inferParserType, ParserBuilder } from './parsers'
 import { renderQueryString } from './url-encoding'
 
@@ -16,7 +16,7 @@ export function createSerializer<
     urlKeys?: Partial<Record<keyof Parsers, string>>
   } = {}
 ) {
-  type Values = Partial<inferParserType<Parsers>>
+  type Values = Partial<Nullable<inferParserType<Parsers>>>
 
   /**
    * Generate a query string for the given values.

packages/nuqs/src/tests/serializer.test-d.ts

@@ -48,3 +48,16 @@ import { createSerializer, parseAsInteger, parseAsString } from '../../dist'
     serialize({ nope: null })
   })
 }
+
+// It accepts null for values
+{
+  const serialize = createSerializer({
+    foo: parseAsInteger,
+    bar: parseAsInteger.withDefault(0)
+  })
+  // Should accept number | null | undefined
+  expectType<string>(serialize({ foo: null }))
+  expectType<string>(serialize({ foo: undefined }))
+  expectType<string>(serialize({ bar: null }))
+  expectType<string>(serialize({ bar: undefined }))
+}