Fix #4701: viewcode: Misplaced `<div>` in viewcode html output

CHANGES

@@ -20,6 +20,7 @@ Bugs fixed
 * #4685: autosummary emits meaningless warnings
 * autodoc: crashed when invalid options given
 * pydomain: always strip parenthesis if empty (refs: #1042)
+* #4701: viewcode: Misplaced ``<div>`` in viewcode html output
 
 Testing
 --------

sphinx/ext/viewcode.py

@@ -178,7 +178,7 @@ def collect_pages(app):
                 '<div class="viewcode-block" id="%s"><a class="viewcode-back" '
                 'href="%s">%s</a>' % (name, backlink, _('[docs]')) +
                 lines[start])
-            lines[min(end - 1, maxindex)] += '</div>'
+            lines[min(end, maxindex)] += '</div>'
         # try to find parents (for submodules)
         parents = []
         parent = modname

tests/test_ext_viewcode.py

@@ -38,6 +38,17 @@ def test_viewcode(app, status, warning):
     # the next assert fails, until the autodoc bug gets fixed
     assert result.count('this is the class attribute class_attr') == 2
 
+    result = (app.outdir / '_modules/spam/mod1.html').text(encoding='utf-8')
+    result = re.sub('<span class=".*?">', '<span>', result)  # filter pygments classes
+    assert ('<div class="viewcode-block" id="Class1"><a class="viewcode-back" '
+            'href="../../index.html#spam.Class1">[docs]</a>'
+            '<span>@decorator</span>\n'
+            '<span>class</span> <span>Class1</span>'
+            '<span>(</span><span>object</span><span>):</span>\n'
+            '    <span>&quot;&quot;&quot;</span>\n'
+            '<span>    this is Class1</span>\n'
+            '<span>    &quot;&quot;&quot;</span></div>\n') in result
+
 
 @pytest.mark.sphinx(testroot='ext-viewcode', tags=['test_linkcode'])
 def test_linkcode(app, status, warning):