Close sphinx-doc#6837: LaTeX: Support a nested table

CHANGES

@@ -31,6 +31,7 @@ Features added
 * #1331: Add new config variable: :confval:`user_agent`
 * #6000: LaTeX: have backslash also be an inline literal word wrap break
   character
+* #6837: LaTeX: Support a nested table
 * #6812: Improve a warning message when extensions are not parallel safe
 * #6818: Improve Intersphinx performance for multiple remote inventories.
 

sphinx/writers/latex.py

@@ -657,7 +657,7 @@ def __init__(self, document, builder):
                                                        latex_engine=self.config.latex_engine)
         self.context = []                   # type: List[Any]
         self.descstack = []                 # type: List[str]
-        self.table = None                   # type: Table
+        self.tables = []                    # type: List[Table]
         self.next_table_colspec = None      # type: str
         self.bodystack = []                 # type: List[List[str]]
         self.footnote_restricted = None     # type: nodes.Element
@@ -806,6 +806,15 @@ def render(self, template_name, variables):
 
         return renderer.render(template_name, variables)
 
+    @property
+    def table(self):
+        # type: () -> Table
+        """Get current table."""
+        if self.tables:
+            return self.tables[-1]
+        else:
+            return None
+
     def visit_document(self, node):
         # type: (nodes.Element) -> None
         self.curfilestack.append(node.get('docname', ''))
@@ -1161,11 +1170,21 @@ def visit_tabular_col_spec(self, node):
 
     def visit_table(self, node):
         # type: (nodes.Element) -> None
-        if self.table:
+        if len(self.tables) == 1:
+            if self.table.get_table_type() == 'longtype':
+                raise UnsupportedError(
+                    '%s:%s: longtype does not support nesting a table.' %
+                    (self.curfilestack[-1], node.line or ''))
+            else:
+                # change type of parent table to tabular
+                # see https://groups.google.com/d/msg/sphinx-users/7m3NeOBixeo/9LKP2B4WBQAJ
+                self.table.has_problematic = True
+        elif len(self.tables) > 2:
             raise UnsupportedError(
-                '%s:%s: nested tables are not yet implemented.' %
+                '%s:%s: deeply nested tables are not yet implemented.' %
                 (self.curfilestack[-1], node.line or ''))
-        self.table = Table(node)
+
+        self.tables.append(Table(node))
         if self.next_table_colspec:
             self.table.colspec = '{%s}\n' % self.next_table_colspec
             if 'colwidths-given' in node.get('classes', []):
@@ -1183,7 +1202,7 @@ def depart_table(self, node):
         self.body.append(table)
         self.body.append("\n")
 
-        self.table = None
+        self.tables.pop()
 
     def visit_colspec(self, node):
         # type: (nodes.Element) -> None