feat[isPartialOf]: discover symbol properties in pred.predObj

Author: Milly

is/__snapshots__/partial_of_test.ts.snap

@@ -23,3 +23,27 @@ snapshot[`isPartialOf<T> > returns properly named predicate function 2`] = `
   d: asOptional(asReadonly(isString))
 })"
 `;
+
+snapshot[`isPartialOf<T> > with symbol properties > returns properly named predicate function 1`] = `
+"isObjectOf({
+  a: asOptional(isNumber),
+  Symbol(b): asOptional(isUnionOf([
+    isString,
+    isUndefined
+  ])),
+  Symbol(c): asOptional(isBoolean),
+  Symbol(c): asOptional(asReadonly(isString))
+})"
+`;
+
+snapshot[`isPartialOf<T> > with symbol properties > returns properly named predicate function 2`] = `
+"isObjectOf({
+  a: asOptional(isNumber),
+  Symbol(b): asOptional(isUnionOf([
+    isString,
+    isUndefined
+  ])),
+  Symbol(c): asOptional(isBoolean),
+  Symbol(c): asOptional(asReadonly(isString))
+})"
+`;

is/partial_of.ts

@@ -42,9 +42,14 @@ export function isPartialOf<
 ):
   & Predicate<FlatType<Partial<T>>>
   & IsPredObj<P> {
-  const predObj = Object.fromEntries(
-    Object.entries(pred.predObj).map(([k, v]) => [k, asOptional(v)]),
-  ) as Record<PropertyKey, Predicate<unknown>>;
+  const keys = [
+    ...Object.keys(pred.predObj),
+    ...Object.getOwnPropertySymbols(pred.predObj),
+  ];
+  const predObj: Record<PropertyKey, Predicate<unknown>> = { ...pred.predObj };
+  for (const key of keys) {
+    predObj[key] = asOptional(predObj[key]);
+  }
   return isObjectOf(predObj) as
     & Predicate<FlatType<Partial<T>>>
     & IsPredObj<P>;

is/partial_of_test.ts

@@ -47,4 +47,55 @@ Deno.test("isPartialOf<T>", async (t) => {
       >(true);
     }
   });
+
+  await t.step("with symbol properties", async (t) => {
+    const b = Symbol("b");
+    const c = Symbol("c");
+    const d = Symbol("c");
+    const pred = is.ObjectOf({
+      a: is.Number,
+      [b]: is.UnionOf([is.String, is.Undefined]),
+      [c]: as.Optional(is.Boolean),
+      [d]: as.Readonly(is.String),
+    });
+
+    await t.step("returns properly named predicate function", async (t) => {
+      await assertSnapshot(t, isPartialOf(pred).name);
+      await assertSnapshot(t, isPartialOf(isPartialOf(pred)).name);
+    });
+
+    await t.step("returns true on Partial<T> object", () => {
+      assertEquals(
+        isPartialOf(pred)({ a: undefined, [b]: undefined, [c]: undefined }),
+        true,
+      );
+      assertEquals(isPartialOf(pred)({}), true);
+    });
+
+    await t.step("returns false on non Partial<T> object", () => {
+      assertEquals(isPartialOf(pred)("a"), false, "Value is not an object");
+      assertEquals(
+        isPartialOf(pred)({ a: 0, [b]: "a", [c]: "" }),
+        false,
+        "Object have a different type property",
+      );
+    });
+
+    await t.step("predicated type is correct", () => {
+      const a: unknown = { a: 0, [b]: "a", [c]: true };
+      if (isPartialOf(pred)(a)) {
+        assertType<
+          Equal<
+            typeof a,
+            Partial<{
+              a: number;
+              [b]: string;
+              [c]: boolean;
+              readonly [d]: string;
+            }>
+          >
+        >(true);
+      }
+    });
+  });
 });