feat(lottery): avoid duplications of the selected reviewers (#38)

__tests__/lottery.test.ts

@@ -7,6 +7,10 @@ const prNumber = 123
 const ref = 'refs/pull/branch-name'
 const basePull = {number: prNumber, head: {ref}}
 
+function hasDuplicates(array: string[]): boolean {
+  return (new Set(array)).size !== array.length;
+}
+
 const mockGetPull = (pull: Pull) =>
   nock('https://api.github.com')
     .get('/repos/uesteibar/repository/pulls')
@@ -57,6 +61,57 @@ test('selects reviewers from a pool of users, ignoring author', async () => {
   nock.cleanAll()
 })
 
+test('selects reviewers from a pool of users, ignoring author and the selected reviewers from another group', async () => {
+  const pull = {
+    ...basePull,
+    user: { login: 'author' },
+    draft: false,
+  };
+
+  const getPullMock = mockGetPull(pull);
+
+  const candidatesTeamA = ['A', 'B', 'author'];
+  const candidatesTeamB = ['C', 'D', 'author'];
+  const allCandidates = ['A', 'B', 'C', 'D', 'author'];
+
+  const postReviewersMock = nock('https://api.github.com')
+    .post(`/repos/uesteibar/repository/pulls/${prNumber}/requested_reviewers`, (body): boolean => {
+      body.reviewers.forEach((reviewer: string) => {
+        expect(allCandidates).toContain(reviewer);
+        expect(reviewer).not.toEqual('author');
+      });
+      expect(body.reviewers.length).toEqual(4);
+      expect(hasDuplicates(body.reviewers)).toBe(false);
+      return true;
+    })
+    .reply(200, pull);
+
+  const config = {
+    groups: [
+      {
+        name: 'Test-A',
+        reviewers: 2,
+        usernames: candidatesTeamA,
+      },
+      {
+        name: 'Test-B',
+        reviewers: 2,
+        usernames: candidatesTeamB,
+      },
+    ],
+  };
+
+  await runLottery(octokit, config, {
+    repository: 'uesteibar/repository',
+    ref,
+  });
+
+  getPullMock.done();
+  postReviewersMock.done();
+
+  nock.cleanAll();
+});
+
 test("doesn't assign reviewers if the PR is in draft state", async () => {
   const pull = {
     ...basePull,

src/lottery.ts

@@ -88,7 +88,7 @@ class Lottery {
 
         if (reviewersToRequest) {
           selected = selected.concat(
-            this.pickRandom(usernames, reviewersToRequest, author)
+            this.pickRandom(usernames, reviewersToRequest, selected.concat(author))
           )
         }
       }
@@ -100,10 +100,10 @@ class Lottery {
     return selected
   }
 
-  pickRandom(items: string[], n: number, ignore: string): string[] {
+  pickRandom(items: string[], n: number, ignore: string[]): string[] {
     const picks: string[] = []
 
-    const candidates = items.filter(item => item !== ignore)
+    const candidates = items.filter(item => !ignore.includes(item));
 
     while (picks.length < n) {
       const random = Math.floor(Math.random() * candidates.length)