Fix pagination loop termination with since filter

pkg/github/client.go

@@ -28,15 +28,28 @@ func (f *IssueFetcher) FetchIssues(ctx context.Context, owner, repo string, sinc
 	}
 
 	var allIssues []*github.Issue
+	seenIssueIDs := make(map[int64]struct{})
 	for {
 		issues, resp, err := f.client.Issues.ListByRepository(ctx, owner, repo, opt)
 		if err != nil {
 			return nil, fmt.Errorf("failed to list issues: %w", err)
 		}
-		allIssues = append(allIssues, issues...)
+		for _, issue := range issues {
+			id := issue.GetID()
+			if id != 0 {
+				if _, ok := seenIssueIDs[id]; ok {
+					continue
+				}
+				seenIssueIDs[id] = struct{}{}
+			}
+			allIssues = append(allIssues, issue)
+		}
 		if resp.NextPage == 0 {
 			break
 		}
+		if resp.NextPage <= opt.Page {
+			return nil, fmt.Errorf("pagination did not advance: current page %d, next page %d", opt.Page, resp.NextPage)
+		}
 		opt.Page = resp.NextPage
 	}
 	return allIssues, nil

pkg/github/client_test.go

@@ -176,6 +176,111 @@ func TestFetchIssues_EmptyPageWithNext(t *testing.T) {
 	}
 }
 
+func TestFetchIssues_DetectsNonAdvancingPaginationWithSince(t *testing.T) {
+	sinceTime := time.Now().Add(-24 * time.Hour).Truncate(time.Second)
+	sinceStr := sinceTime.Format(time.RFC3339)
+	requests := 0
+
+	var server *httptest.Server
+	server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		if requests > 2 {
+			t.Fatal("pagination loop was not terminated")
+		}
+
+		q := r.URL.Query()
+		if q.Get("since") != sinceStr {
+			t.Errorf("expected since parameter %q, got %q", sinceStr, q.Get("since"))
+		}
+
+		issues := []*github.Issue{
+			{ID: github.Int64(1), Title: github.String("Issue 1")},
+		}
+
+		linkHeader := fmt.Sprintf("<%s?page=1&since=%s>; rel=\"next\"", server.URL+r.URL.Path, url.QueryEscape(sinceStr))
+		w.Header().Set("Link", linkHeader)
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(issues)
+	}))
+	defer server.Close()
+
+	httpClient := server.Client()
+	client := github.NewClient(httpClient)
+	baseURL, _ := url.Parse(server.URL + "/")
+	client.BaseURL = baseURL
+
+	fetcher := NewIssueFetcher(client)
+	_, err := fetcher.FetchIssues(context.Background(), "owner", "repo", sinceTime, 2)
+	if err == nil {
+		t.Fatal("expected pagination loop error, got nil")
+	}
+
+	if !strings.Contains(err.Error(), "pagination did not advance") {
+		t.Errorf("expected pagination loop error, got: %v", err)
+	}
+	if requests != 2 {
+		t.Errorf("expected 2 requests before loop detection, got %d", requests)
+	}
+}
+
+func TestFetchIssues_DeduplicatesIssuesAcrossPages(t *testing.T) {
+	var server *httptest.Server
+	server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		q := r.URL.Query()
+		pageStr := q.Get("page")
+		page := 1
+		if pageStr != "" {
+			var err error
+			page, err = strconv.Atoi(pageStr)
+			if err != nil {
+				t.Fatalf("invalid page parameter: %v", err)
+			}
+		}
+
+		var issues []*github.Issue
+		switch page {
+		case 1:
+			issues = []*github.Issue{
+				{ID: github.Int64(1), Title: github.String("Issue 1")},
+				{ID: github.Int64(2), Title: github.String("Issue 2")},
+			}
+			w.Header().Set("Link", fmt.Sprintf("<%s?page=2>; rel=\"next\"", server.URL+r.URL.Path))
+		case 2:
+			issues = []*github.Issue{
+				{ID: github.Int64(2), Title: github.String("Issue 2 duplicate")},
+				{ID: github.Int64(3), Title: github.String("Issue 3")},
+			}
+		default:
+			t.Fatalf("unexpected page request: %d", page)
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(issues)
+	}))
+	defer server.Close()
+
+	httpClient := server.Client()
+	client := github.NewClient(httpClient)
+	baseURL, _ := url.Parse(server.URL + "/")
+	client.BaseURL = baseURL
+
+	fetcher := NewIssueFetcher(client)
+	issues, err := fetcher.FetchIssues(context.Background(), "owner", "repo", time.Now(), 2)
+	if err != nil {
+		t.Fatalf("FetchIssues failed: %v", err)
+	}
+
+	expectedIDs := []int64{1, 2, 3}
+	if len(issues) != len(expectedIDs) {
+		t.Fatalf("expected %d issues, got %d", len(expectedIDs), len(issues))
+	}
+	for i, issue := range issues {
+		if issue.GetID() != expectedIDs[i] {
+			t.Errorf("at index %d: expected ID %d, got %d", i, expectedIDs[i], issue.GetID())
+		}
+	}
+}
+
 func TestFetchIssues_Integration(t *testing.T) {
 	token := os.Getenv("GITHUB_TOKEN")
 	repoFullName := os.Getenv("GITHUB_REPOSITORY")