BUG: no label render in Styler.to_latex if caption and "longtable" (pandas-dev#43399)

Author: attack68

pandas/io/formats/templates/latex_longtable.tpl

@@ -23,6 +23,11 @@
 {%- if label is not none %}
  \label{{label}}
 {%- endif %} \\
+{% else %}
+{%- set label = parse_table(table_styles, 'label') %}
+{%- if label is not none %}
+\label{{label}} \\
+{% endif %}
 {% endif %}
 {% set toprule = parse_table(table_styles, 'toprule') %}
 {% if toprule is not none %}

pandas/tests/io/formats/style/test_to_latex.py

@@ -109,10 +109,11 @@ def test_position(styler):
     assert "\\end{table}" in styler.to_latex()
 
 
-def test_label(styler):
-    assert "\\label{text}" in styler.to_latex(label="text")
+@pytest.mark.parametrize("env", [None, "longtable"])
+def test_label(styler, env):
+    assert "\n\\label{text}" in styler.to_latex(label="text", environment=env)
     styler.set_table_styles([{"selector": "label", "props": ":{more §text}"}])
-    assert "\\label{more :text}" in styler.to_latex()
+    assert "\n\\label{more :text}" in styler.to_latex(environment=env)
 
 
 def test_position_float_raises(styler):