Add :confval:epub_css_files

CHANGES

@@ -59,7 +59,8 @@ Features added
 * LaTeX: new key ``'fvset'`` for :confval:`latex_elements`. For
   XeLaTeX/LuaLaTeX its default sets ``fanvyvrb`` to use normal, not small,
   fontsize in code-blocks (refs: #4793)
-* Add :confval:`html_css_files` for adding CSS files from configuration
+* Add :confval:`html_css_files` and :confval:`epub_css_files` for adding CSS
+  files from configuration
 
 Bugs fixed
 ----------

doc/config.rst

@@ -1524,6 +1524,14 @@ the `Dublin Core metadata <http://dublincore.org/>`_.
 
    .. versionadded:: 1.1
 
+.. confval:: epub_css_files
+
+   A list of CSS files.  The entry must be a *filename* string or a tuple
+   containing the *filename* string and the *attributes* dictionary.  For more
+   information, see :confval:`html_css_files`.
+
+   .. versionadded:: 1.8
+
 .. confval:: epub_guide
 
    Meta data for the guide element of :file:`content.opf`. This is a

sphinx/builders/epub3.py

@@ -247,6 +247,7 @@ def setup(app):
     app.add_config_value('epub_guide', (), 'env')
     app.add_config_value('epub_pre_files', [], 'env')
     app.add_config_value('epub_post_files', [], 'env')
+    app.add_config_value('epub_css_files', lambda config: config.html_css_files, 'epub')
     app.add_config_value('epub_exclude_files', [], 'env')
     app.add_config_value('epub_tocdepth', 3, 'env')
     app.add_config_value('epub_tocdup', True, 'env')

tests/test_build_epub.py

@@ -317,6 +317,34 @@ def test_epub_writing_mode(app):
     assert 'writing-mode: vertical-rl;' in css
 
 
+@pytest.mark.sphinx('epub', testroot='html_assets')
+def test_epub_assets(app):
+    app.builder.build_all()
+
+    # epub_sytlesheets (same as html_css_files)
+    content = (app.outdir / 'index.xhtml').text()
+    assert ('<link rel="stylesheet" type="text/css" href="_static/css/style.css" />'
+            in content)
+    assert ('<link media="print" rel="stylesheet" title="title" type="text/css" '
+            'href="https://example.com/custom.css" />' in content)
+
+
+@pytest.mark.sphinx('epub', testroot='html_assets',
+                    confoverrides={'epub_css_files': ['css/epub.css']})
+def test_epub_css_files(app):
+    app.builder.build_all()
+
+    # epub_css_files
+    content = (app.outdir / 'index.xhtml').text()
+    assert '<link rel="stylesheet" type="text/css" href="_static/css/epub.css" />' in content
+
+    # files in html_css_files are not outputed
+    assert ('<link rel="stylesheet" type="text/css" href="_static/css/style.css" />'
+            not in content)
+    assert ('<link media="print" rel="stylesheet" title="title" type="text/css" '
+            'href="https://example.com/custom.css" />' not in content)
+
+
 @pytest.mark.sphinx('epub')
 def test_run_epubcheck(app):
     app.build()