Avoid panic when pagination on 0 pages

Fixes gohugoio#948

hugolib/pagination.go

@@ -30,6 +30,8 @@ type pager struct {
 
 type pagers []*pager
 
+var paginatorEmptyPages Pages
+
 type paginator struct {
 	paginatedPages []Pages
 	pagers
@@ -52,6 +54,9 @@ func (p *pager) Url() template.HTML {
 
 // Pages returns the elements on this page.
 func (p *pager) Pages() Pages {
+	if len(p.paginatedPages) == 0 {
+		return paginatorEmptyPages
+	}
 	return p.paginatedPages[p.PageNumber()-1]
 }
 
@@ -233,13 +238,20 @@ func newPaginator(pages Pages, size int, urlFactory paginationUrlFactory) (*pagi
 	split := splitPages(pages, size)
 
 	p := &paginator{total: len(pages), paginatedPages: split, size: size, paginationUrlFactory: urlFactory}
-	pagers := make(pagers, len(split))
 
-	for i := range p.paginatedPages {
-		pagers[i] = &pager{number: (i + 1), paginator: p}
+	var ps pagers
+
+	if len(split) > 0 {
+		ps = make(pagers, len(split))
+		for i := range p.paginatedPages {
+			ps[i] = &pager{number: (i + 1), paginator: p}
+		}
+	} else {
+		ps = make(pagers, 1)
+		ps[0] = &pager{number: 1, paginator: p}
 	}
 
-	p.pagers = pagers
+	p.pagers = ps
 
 	return p, nil
 }

hugolib/pagination_test.go

@@ -76,10 +76,25 @@ func TestPagerNoPages(t *testing.T) {
 	paginator, _ := newPaginator(pages, 5, urlFactory)
 	paginatorPages := paginator.Pagers()
 
-	assert.Equal(t, 0, len(paginatorPages))
+	assert.Equal(t, 1, len(paginatorPages))
 	assert.Equal(t, 0, paginator.TotalNumberOfElements())
 	assert.Equal(t, 5, paginator.PageSize())
 	assert.Equal(t, 0, paginator.TotalPages())
+
+	// pageOne should be nothing but the first
+	pageOne := paginatorPages[0]
+	assert.NotNil(t, pageOne.First())
+	assert.False(t, pageOne.HasNext())
+	assert.False(t, pageOne.HasPrev())
+	assert.Nil(t, pageOne.Next())
+	assert.Equal(t, 1, len(pageOne.Pagers()))
+	assert.Equal(t, 0, len(pageOne.Pages()))
+	assert.Equal(t, 0, pageOne.NumberOfElements())
+	assert.Equal(t, 0, pageOne.TotalNumberOfElements())
+	assert.Equal(t, 0, pageOne.TotalPages())
+	assert.Equal(t, 1, pageOne.PageNumber())
+	assert.Equal(t, 5, pageOne.PageSize())
+
 }
 
 func TestPaginationUrlFactory(t *testing.T) {