Don’t append useless tracks when grid elements are positioned

Fix #2187.

tests/layout/test_grid.py

@@ -988,3 +988,35 @@ def test_grid_template_areas_extra_span_column_dense():
     assert div_e.height == 4
     assert article.height == 4
     assert article.width == 12
+
+
+@assert_no_logs
+def test_grid_gap_explicit_grid_column():
+    # Regression test for https://github.com/Kozea/WeasyPrint/issues/2187
+    page, = render_pages('''
+      <style>
+        @font-face { src: url(weasyprint.otf); font-family: weasyprint }
+        article {
+          display: grid;
+          font-family: weasyprint;
+          font-size: 2px;
+          gap: 2px;
+          grid-template-columns: 1fr;
+          line-height: 1;
+          width: 12px;
+        }
+      </style>
+      <article>
+        <div>a</div>
+        <div style="grid-column: 1">b</div>
+      </article>
+    ''')
+    html, = page.children
+    body, = html.children
+    article, = body.children
+    div_a, div_b = article.children
+    assert div_a.position_x == div_b.position_x == 0
+    assert div_a.position_y == 0
+    assert div_b.position_y == 4
+    assert article.height == 6
+    assert article.width == 12

weasyprint/layout/grid.py

@@ -797,10 +797,7 @@ def grid_layout(context, box, bottom_space, skip_stack, containing_block,
                         break
                 first_diff = first_i + first_size - implicit_first_2
                 if first_diff > 0:
-                    for _ in range(first_diff):
-                        first_tracks.append(next(auto_tracks))
-                        first_tracks.append([])
-                    implicit_first_2 = first_i + first_size
+                    implicit_first_2 += first_diff
                 # 3. Set the item’s row-start line.
                 if first_flow == 'row':
                     x, y = second_i, first_i
@@ -912,10 +909,7 @@ def grid_layout(context, box, bottom_space, skip_stack, containing_block,
                         break
                 first_diff = first_i + first_size - implicit_first_2
                 if first_diff > 0:
-                    for _ in range(first_diff):
-                        first_tracks.append(next(auto_tracks))
-                        first_tracks.append([])
-                    implicit_first_2 = y + height
+                    implicit_first_2 += first_diff
                 # 3. Set the item’s row-start line.
                 children_positions[child] = (x, y, width, height)
             else: