Do not uncomment raw ipynb cells (#1159)

* Add a test to reproduce #1131
* Do not uncomment raw ipynb cells

src/jupytext/cell_reader.py

@@ -862,6 +862,7 @@ def find_cell_end(self, lines):
             if self.metadata.get("active") == "":
                 del self.metadata["active"]
             self.cell_type = "raw"
+            self.comment = ""
         else:
             self.cell_type = "code"
 

tests/functional/others/test_active_cells.py

@@ -291,6 +291,60 @@ def test_active_cells_from_py_percent(
     compare(text2, text)
 
 
+def test_comments_work_in_active_cells_from_py_percent_1131(
+    text="""# %% tags=["active-py"]
+# this is a comment
+""",
+):
+    nb = jupytext.reads(text, "py:percent")
+    assert nb.cells[0].cell_type == "raw"
+    assert nb.cells[0].source == "# this is a comment"
+
+    text2 = jupytext.writes(nb, "py:percent")
+    compare(text2, text)
+
+
+def test_comments_work_in_active_cells_from_py_light_1131(
+    text="""# + tags=["active-py"]
+# this is a comment
+""",
+):
+    nb = jupytext.reads(text, "py:light")
+    assert nb.cells[0].cell_type == "raw"
+    assert nb.cells[0].source == "# this is a comment"
+
+    text2 = jupytext.writes(nb, "py:light")
+    compare(text2, text)
+
+
+def test_comments_plus_code_work_in_active_cells_from_py_percent_1131(
+    text="""# %% tags=["active-py"]
+# this is a comment
+1 + 1
+""",
+):
+    nb = jupytext.reads(text, "py:percent")
+    assert nb.cells[0].cell_type == "raw"
+    assert nb.cells[0].source == "# this is a comment\n1 + 1"
+
+    text2 = jupytext.writes(nb, "py:percent")
+    compare(text2, text)
+
+
+def test_comments_plus_code_work_in_active_cells_from_py_light_1131(
+    text="""# + tags=["active-py"]
+# this is a comment
+1 + 1
+""",
+):
+    nb = jupytext.reads(text, "py:light")
+    assert nb.cells[0].cell_type == "raw"
+    assert nb.cells[0].source == "# this is a comment\n1 + 1"
+
+    text2 = jupytext.writes(nb, "py:light")
+    compare(text2, text)
+
+
 def test_active_cells_from_py_light(
     text="""# + active="py"
 print('should only be displayed in py file')