Improve nullable, optional, and shape

src/test/parse.test.ts

@@ -157,6 +157,56 @@ describe(Parse.shape, () => {
     });
   });
 
+  test("allows nullable entries", () => {
+    const parseThing = Parse.shape({
+      name: Parse.string,
+      another: Parse.nullable(Parse.string),
+    });
+
+    expect(parseThing({ name: "hello", another: null })).toEqual({
+      name: "hello",
+      another: null,
+    });
+  });
+
+  test("nullable entries can accpet undefined when configured as such", () => {
+    const parseThing = Parse.shape({
+      name: Parse.string,
+      another: Parse.nullable(Parse.string, true),
+    });
+
+    const obj = {
+      name: "hello",
+      another: undefined,
+    };
+
+    const result = parseThing(obj);
+
+    expect(result).toEqual({
+      name: "hello",
+      another: null,
+    });
+  });
+
+  test("optional entries can accpet null when configured as such", () => {
+    const parseThing = Parse.shape({
+      name: Parse.string,
+      another: Parse.optional(Parse.string, true),
+    });
+
+    const obj = {
+      name: "hello",
+      another: null,
+    };
+
+    const result = parseThing(obj);
+
+    expect(result).toEqual({
+      name: "hello",
+      another: undefined,
+    });
+  });
+
   test("throws when a required value is missing", () => {
     const parseThing = Parse.shape({
       name: Parse.string,
@@ -195,12 +245,20 @@ describe(Parse.optional, () => {
   test("Parses undefined values", () => {
     expect(Parse.optional(Parse.string)(undefined)).toBeUndefined();
   });
+
+  test("Parses null values when configured", () => {
+    expect(Parse.optional(Parse.string, true)(null)).toBeUndefined();
+  });
 });
 
 describe(Parse.nullable, () => {
   test("Parses null values", () => {
     expect(Parse.nullable(Parse.string)(null)).toBeNull();
   });
+
+  test("Parses undefined values when configured", () => {
+    expect(Parse.nullable(Parse.string, true)(undefined)).toBeNull();
+  });
 });
 
 describe(Parse.defaulted, () => {