Adds support for header_value for export header

Author: 5tefan

django_tables2/columns/base.py

@@ -338,6 +338,26 @@ def header(self):
         """
         return self.verbose_name
 
+    @property
+    def header_value(self):
+        """
+        The value used for the column heading in exports.
+
+        By default this returns `~.Column.header`.
+
+        :returns: `unicode` or `None`
+
+        .. note::
+
+            This property typically is not accessed directly when a table is
+            rendered. Instead, `.BoundColumn.header_value` is accessed which
+            in turn accesses this property. This allows the header to fallback
+            to the column name (it is only available on a `.BoundColumn` object
+            hence accessing that first) when this property doesn't return something
+            useful.
+        """
+        return self.header
+
     def footer(self, bound_column, table):
         """Return the content of the footer, if specified."""
         footer_kwargs = {"column": self, "bound_column": bound_column, "table": table}
@@ -556,6 +576,14 @@ def header(self):
         # fall back to automatic best guess
         return self.verbose_name
 
+    @property
+    def header_value(self):
+        """The contents of the header for this column in an export."""
+        column_header_value = self.column.header_value
+        if column_header_value:
+            return column_header_value
+        return self.header
+
     @property
     def footer(self):
         """The contents of the footer cell for this column."""

django_tables2/tables.py

@@ -493,7 +493,7 @@ def value_name(self, value):
             if not (column.column.exclude_from_export or column.name in exclude_columns)
         ]
 
-        yield [force_str(column.header, strings_only=True) for column in columns]
+        yield [force_str(column.header_value, strings_only=True) for column in columns]
 
         for row in self.rows:
             yield [

docs/pages/custom-data.rst

@@ -151,9 +151,9 @@ Please refer to `.Table.as_values` for an example.
 Subclassing `.Column`
 ---------------------
 
-Defining a column subclass allows functionality to be reused across tables.
-Columns have a `render` method that behaves the same as :ref:`table.render_foo`
-methods on tables::
+Defining a column subclass allows further customization and functionality to
+be reused across tables. Columns have a `render` method that behaves the same
+as :ref:`table.render_foo` methods on tables::
 
     >>> import django_tables2 as tables
     >>>
@@ -186,3 +186,19 @@ For complicated columns, you may want to return HTML from the
     ...     def render(self, value):
     ...         return format_html('<img src="/media/img/{}.jpg" />', value)
     ...
+
+When subclassing a column, the header in the html table can be customized by
+overriding :meth:`~Column.header`. The header value for exports can be independently
+customized using  :meth:`~Column.render_value`.
+
+
+    >>> from django.utils.html import format_html
+    >>>
+    >>> class PartyColumn(tables.Column):
+    ...     @property
+    ...     def header(self):
+    ...         return format_html('<div><marquee>PaRtY!</marquee></div>')
+    ...
+    ...     @property
+    ...     def header_value(self):
+    ...         return "party"

docs/pages/export.rst

@@ -80,6 +80,10 @@ By default, it just calls the `render()` method on that column.
 If your custom column produces HTML, you should override this method and return
 the actual value.
 
+For column headers, similarly sometimes :ref:Column.header`-may include html which
+would be inappropriate to include in an export. For this case, the `:ref:Column.header_value`
+can be used to override the column header only in exports.
+
 
 Including and excluding columns
 -------------------------------

tests/test_core.py

@@ -661,6 +661,22 @@ def value_country(self, value):
 
         self.assertEqual(list(Table(self.AS_VALUES_DATA).as_values()), expected)
 
+    def test_as_value_header_value(self):
+        class CustomColumn(tables.Column):
+
+            @property
+            def header_value(self):
+                return "CUSTOM"
+
+        class Table(tables.Table):
+            name = tables.Column()
+            country = CustomColumn()
+
+        expected = [["Name", "CUSTOM"]] + [[r["name"], r["country"]] for r in self.AS_VALUES_DATA]
+        table = Table(self.AS_VALUES_DATA)
+
+        self.assertEqual(list(table.as_values()), expected)
+
     def test_as_values_accessor_relation(self):
         programmer = Occupation.objects.create(name="Programmer")
         henk = Person.objects.create(