BUG: to_html misses truncation indicators (...) when index=False

doc/source/whatsnew/v0.24.0.txt

@@ -1288,6 +1288,7 @@ Notice how we now instead output ``np.nan`` itself instead of a stringified form
 - :func:`read_sas()` will correctly parse sas7bdat files with many columns (:issue:`22628`)
 - :func:`read_sas()` will correctly parse sas7bdat files with data page types having also bit 7 set (so page type is 128 + 256 = 384) (:issue:`16615`)
 - Bug in :meth:`detect_client_encoding` where potential ``IOError`` goes unhandled when importing in a mod_wsgi process due to restricted access to stdout. (:issue:`21552`)
+- Bug in :func:`to_html()` with ``index=False`` misses truncation indicators (...) on truncated DataFrame (:issue:`15019`, :issue:`22783`)
 - Bug in :func:`to_string()` that broke column alignment when ``index=False`` and width of first column's values is greater than the width of first column's header (:issue:`16839`, :issue:`13032`)
 - Bug in :func:`DataFrame.to_csv` where a single level MultiIndex incorrectly wrote a tuple. Now just the value of the index is written (:issue:`19589`).
 - Bug in :meth:`HDFStore.append` when appending a :class:`DataFrame` with an empty string column and ``min_itemsize`` < 8 (:issue:`12242`)

pandas/io/formats/html.py

@@ -305,6 +305,8 @@ def _column_header():
             align = self.fmt.justify
 
             if truncate_h:
+                if self.fmt.index is False:
+                    row_levels = 0
                 ins_col = row_levels + self.fmt.tr_col_num
                 col_row.insert(ins_col, '...')
 
@@ -342,8 +344,21 @@ def _write_body(self, indent):
             else:
                 self._write_regular_rows(fmt_values, indent)
         else:
-            for i in range(min(len(self.frame), self.max_rows)):
-                row = [fmt_values[j][i] for j in range(len(self.columns))]
+            truncate_h = self.fmt.truncate_h
+            truncate_v = self.fmt.truncate_v
+            ncols = len(self.fmt.tr_frame.columns)
+            nrows = len(self.fmt.tr_frame)
+
+            row = []
+            for i in range(nrows):
+                if truncate_v and i == (self.fmt.tr_row_num):
+                    str_sep_row = ['...'] * len(row)
+                    self.write_tr(str_sep_row, indent,
+                                  self.indent_delta, tags=None)
+                row = [fmt_values[j][i] for j in range(ncols)]
+                if truncate_h:
+                    dot_col_ix = self.fmt.tr_col_num
+                    row.insert(dot_col_ix, '...')
                 self.write_tr(row, indent, self.indent_delta, tags=None)
 
         indent -= self.indent_delta

pandas/tests/io/formats/data/gh15019_expected_output.html

@@ -0,0 +1,30 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th>0</th>
+      <th>1</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>1.764052</td>
+      <td>0.400157</td>
+    </tr>
+    <tr>
+      <td>0.978738</td>
+      <td>2.240893</td>
+    </tr>
+    <tr>
+      <td>...</td>
+      <td>...</td>
+    </tr>
+    <tr>
+      <td>0.950088</td>
+      <td>-0.151357</td>
+    </tr>
+    <tr>
+      <td>-0.103219</td>
+      <td>0.410599</td>
+    </tr>
+  </tbody>
+</table>

pandas/tests/io/formats/data/gh22783_expected_output.html

@@ -0,0 +1,27 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th>0</th>
+      <th>1</th>
+      <th>...</th>
+      <th>3</th>
+      <th>4</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>1.764052</td>
+      <td>0.400157</td>
+      <td>...</td>
+      <td>2.240893</td>
+      <td>1.867558</td>
+    </tr>
+    <tr>
+      <td>-0.977278</td>
+      <td>0.950088</td>
+      <td>...</td>
+      <td>-0.103219</td>
+      <td>0.410599</td>
+    </tr>
+  </tbody>
+</table>

pandas/tests/io/formats/test_to_html.py

@@ -22,6 +22,28 @@
     pass
 
 
+def expected_html(datapath, name):
+    """
+    Read HTML file from formats data directory.
+
+    Parameters
+    ----------
+    datapath : pytest fixture
+        The datapath fixture injected into a test by pytest.
+    name : str
+        The name of the HTML file without the suffix.
+
+    Returns
+    -------
+    str : contents of HTML file.
+    """
+    filename = '.'.join([name, 'html'])
+    filepath = datapath('io', 'formats', 'data', filename)
+    with open(filepath) as f:
+        html = f.read()
+    return html.rstrip()
+
+
 class TestToHTML(object):
 
     def test_to_html_with_col_space(self):
@@ -1881,6 +1903,22 @@ def test_to_html_multiindex_max_cols(self):
         </table>""")
         assert result == expected
 
+    def test_to_html_truncation_index_false_max_rows(self, datapath):
+        # GH 15019
+        np.random.seed(seed=0)
+        df = pd.DataFrame(np.random.randn(5, 2))
+        result = df.to_html(max_rows=4, index=False)
+        expected = expected_html(datapath, 'gh15019_expected_output')
+        assert result == expected
+
+    def test_to_html_truncation_index_false_max_cols(self, datapath):
+        # GH 22783
+        np.random.seed(seed=0)
+        df = pd.DataFrame(np.random.randn(2, 5))
+        result = df.to_html(max_cols=4, index=False)
+        expected = expected_html(datapath, 'gh22783_expected_output')
+        assert result == expected
+
     def test_to_html_notebook_has_style(self):
         df = pd.DataFrame({"A": [1, 2, 3]})
         result = df.to_html(notebook=True)