From 6c3f0d2b1d890954a61c3b168853b853b8e929c7 Mon Sep 17 00:00:00 2001
From: Jan Molak <1089173+jan-molak@users.noreply.github.com>
Date: Sun, 5 Jun 2022 23:00:08 +0100
Subject: [PATCH] fix(tinytype): toJSON correctly serialises null and undefined
 values

---
 spec/TinyType.spec.ts | 20 ++++++++++++++++++++
 src/TinyType.ts       | 11 +++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/spec/TinyType.spec.ts b/spec/TinyType.spec.ts
index 1e585f22..5ee7fd62 100644
--- a/spec/TinyType.spec.ts
+++ b/spec/TinyType.spec.ts
@@ -327,6 +327,26 @@ describe('TinyType', () => {
                     });
                 });
 
+                it('should serialise null and undefined', () => {
+                    interface NotesType {
+                        nullValue: any;
+                        undefinedValue: any;
+                    }
+
+                    class Notes extends TinyTypeOf<NotesType>() {
+                    }
+
+                    const notes = new Notes({
+                        nullValue: null,
+                        undefinedValue: undefined,
+                    });
+
+                    expect(notes.toJSON()).to.deep.equal({
+                        nullValue: null,
+                        undefinedValue: undefined,
+                    });
+                });
+
                 it(`should JSON.stringify any object that can't be represented in a more sensible way`, () => {
                     class TT extends TinyTypeOf<number>() {
                     }
diff --git a/src/TinyType.ts b/src/TinyType.ts
index dae08471..4ca9d69c 100644
--- a/src/TinyType.ts
+++ b/src/TinyType.ts
@@ -178,6 +178,13 @@ function isSerialisableNumber(value: unknown): value is number {
 }
 
 function isSerialisablePrimitive(value: unknown): value is string | boolean | number | null | undefined {
-    return ['string', 'boolean', 'null', 'undefined'].includes(typeof value)
-        || isSerialisableNumber(value);
+    if (['string', 'boolean'].includes(typeof value)) {
+        return true;
+    }
+
+    if (value === null || value === undefined) {
+        return true;
+    }
+
+    return isSerialisableNumber(value);
 }