fix(set): updating an array

src/collection/collection.test.ts

@@ -408,13 +408,59 @@ describe("set", () => {
       { color: "red", contents: ["apple", "orange", "banana"] },
     ]);
 
-    const $patch = $.get({ color: "red" })
+    $.get({ color: "red" })
       .set({ contents: ["orange", "banana"] })
       .commit();
 
-    console.log($patch);
+    expect($.get({ color: "red" }).data).toEqual({
+      color: "red",
+      contents: ["orange", "banana"],
+    });
+  });
+
+  it("updates an empty array", () => {
+    const $ = new Collection<{
+      color: string;
+      contents: string[];
+      animal: string;
+    }>(
+      [
+        { color: "green", contents: ["apple"], animal: "gorilla" },
+        { color: "red", contents: [], animal: "monkey" },
+      ],
+      { primaryKey: "color" }
+    );
+
+    $.get({ color: "red" })
+      .set({ contents: ["orange", "banana"], animal: "giraffe" })
+      .commit();
+
+    expect($.get({ color: "red" }).data).toEqual({
+      animal: "giraffe",
+      color: "red",
+      contents: ["orange", "banana"],
+    });
+  });
+
+  it("adds to an existing array", () => {
+    const $ = new Collection<{
+      color: string;
+      contents: string[];
+      animal: string;
+    }>(
+      [
+        { color: "green", contents: ["apple"], animal: "gorilla" },
+        { color: "red", contents: ["pea"], animal: "monkey" },
+      ],
+      { primaryKey: "color" }
+    );
+
+    $.get({ color: "red" })
+      .set({ contents: ["orange", "banana"], animal: "giraffe" })
+      .commit();
 
     expect($.get({ color: "red" }).data).toEqual({
+      animal: "giraffe",
       color: "red",
       contents: ["orange", "banana"],
     });

src/data/hash-table/table.ts

@@ -432,10 +432,23 @@ export class HashTable<
     const node = this.items[$id];
 
     if ($id && node && path.length > 0) {
-      // adding a new attribute to an existing node
-      const attribute = path.join(".");
       const original = cloneDeep(node.data);
-      set(this.items[$id].data as unknown as object, attribute, value);
+      const isAddToArrayOperation = path[path.length - 1] === "-";
+      const attribute = (isAddToArrayOperation ? path.slice(0, -1) : path).join(
+        "."
+      );
+      const { data } = this.items[$id];
+
+      if (isAddToArrayOperation) {
+        // add element to an array
+        const existing = dot(
+          data as Record<string, unknown>,
+          attribute
+        ) as unknown[];
+        set(data, attribute, [...existing, value]);
+      } else {
+        set(data as unknown as object, attribute, value);
+      }
 
       return {
         operation: "addAttribute",