Fix broken LaTeX code is generated if unknown language is given

CHANGES

@@ -51,6 +51,7 @@ Bugs fixed
 * #1899: Ensure list is sent to OptParse.
 * #2164: Fix wrong check for pdftex inside sphinx.sty (for graphicx package option).
 * #2165, #2218: Remove faulty and non-need conditional from sphinx.sty.
+* Fix broken LaTeX code is generated if unknown language is given
 
 Documentation
 -------------

sphinx/writers/latex.py

@@ -327,6 +327,7 @@ class LaTeXTranslator(nodes.NodeVisitor):
             else:
                 self.builder.warn('no Babel option known for language %r' %
                                   builder.config.language)
+                self.elements['classoptions'] += ',english'  # fallback to english
             self.elements['shorthandoff'] = babel.get_shorthandoff()
             self.elements['fncychap'] = '\\usepackage[Sonny]{fncychap}'
 
@@ -481,7 +482,7 @@ class LaTeXTranslator(nodes.NodeVisitor):
         else:
             if builder.config.language:
                 language = ExtBabel(builder.config.language).get_language()
-                if language is None:
+                if not language:
                     language = 'english'
             else:
                 language = 'english'

tests/roots/test-contentsname/conf.py

@@ -1,5 +0,0 @@
-# -*- coding: utf-8 -*-
-
-master_doc = 'index'
-html_theme = 'classic'
-exclude_patterns = ['_build']

tests/roots/test-latex-babel/conf.py

@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+
+master_doc = 'index'
+numfig_format = {
+    'figure': 'Fig. %s',
+    'table': 'Table. %s',
+    'code-block': 'List.',
+}

tests/test_build_latex.py

@@ -273,26 +273,94 @@ def test_latex_add_latex_package(app, status, warning):
     assert '\\usepackage[baz]{bar}' in result
 
 
-@with_app(buildername='latex', testroot='contentsname')
-def test_contentsname(app, status, warning):
+@with_app(buildername='latex', testroot='latex-babel')
+def test_babel_with_no_language_settings(app, status, warning):
     app.builder.build_all()
     result = (app.outdir / 'Python.tex').text(encoding='utf8')
     print(result)
     print(status.getvalue())
     print(warning.getvalue())
-    assert ('\\addto\\captionsenglish{\\renewcommand{\\contentsname}{Table of content}}'
+    assert '\\documentclass[letterpaper,10pt,english]{sphinxmanual}' in result
+    assert '\\usepackage{babel}' in result
+    assert '\\usepackage{times}' in result
+    assert '\\usepackage[Bjarne]{fncychap}' in result
+    assert ('\\addto\\captionsenglish{\\renewcommand{\\contentsname}{Table of content}}\n'
             in result)
+    assert '\\addto\\captionsenglish{\\renewcommand{\\figurename}{Fig. }}\n' in result
+    assert '\\addto\\captionsenglish{\\renewcommand{\\tablename}{Table. }}\n' in result
 
 
-@with_app(buildername='latex', testroot='contentsname',
-          confoverrides={'language': 'ja'})
-def test_contentsname_with_language_ja(app, status, warning):
+@with_app(buildername='latex', testroot='latex-babel',
+          confoverrides={'language': 'de'})
+def test_babel_with_language_de(app, status, warning):
     app.builder.build_all()
     result = (app.outdir / 'Python.tex').text(encoding='utf8')
     print(result)
     print(status.getvalue())
     print(warning.getvalue())
-    assert '\\renewcommand{\\contentsname}{Table of content}' in result
+    assert '\\documentclass[letterpaper,10pt,ngerman]{sphinxmanual}' in result
+    assert '\\usepackage{babel}' in result
+    assert '\\usepackage{times}' in result
+    assert '\\usepackage[Sonny]{fncychap}' in result
+    assert ('\\addto\\captionsngerman{\\renewcommand{\\contentsname}{Table of content}}\n'
+            in result)
+    assert '\\addto\\captionsngerman{\\renewcommand{\\figurename}{Fig. }}\n' in result
+    assert '\\addto\\captionsngerman{\\renewcommand{\\tablename}{Table. }}\n' in result
+
+
+@with_app(buildername='latex', testroot='latex-babel',
+          confoverrides={'language': 'ru'})
+def test_babel_with_language_ru(app, status, warning):
+    app.builder.build_all()
+    result = (app.outdir / 'Python.tex').text(encoding='utf8')
+    print(result)
+    print(status.getvalue())
+    print(warning.getvalue())
+    assert '\\documentclass[letterpaper,10pt,russian]{sphinxmanual}' in result
+    assert '\\usepackage{babel}' in result
+    assert '\\usepackage{times}' not in result
+    assert '\\usepackage[Sonny]{fncychap}' in result
+    assert ('\\addto\\captionsrussian{\\renewcommand{\\contentsname}{Table of content}}\n'
+            in result)
+    assert '\\addto\\captionsrussian{\\renewcommand{\\figurename}{Fig. }}\n' in result
+    assert '\\addto\\captionsrussian{\\renewcommand{\\tablename}{Table. }}\n' in result
+
+
+@with_app(buildername='latex', testroot='latex-babel',
+          confoverrides={'language': 'ja'})
+def test_babel_with_language_ja(app, status, warning):
+    app.builder.build_all()
+    result = (app.outdir / 'Python.tex').text(encoding='utf8')
+    print(result)
+    print(status.getvalue())
+    print(warning.getvalue())
+    assert '\\documentclass[letterpaper,10pt,dvipdfmx]{sphinxmanual}' in result
+    assert '\\usepackage{babel}' not in result
+    assert '\\usepackage{times}' in result
+    assert '\\usepackage[Sonny]{fncychap}' not in result
+    assert '\\renewcommand{\\contentsname}{Table of content}\n' in result
+    assert '\\renewcommand{\\figurename}{Fig. }\n' in result
+    assert '\\renewcommand{\\tablename}{Table. }\n' in result
+
+
+@with_app(buildername='latex', testroot='latex-babel',
+          confoverrides={'language': 'unknown'})
+def test_babel_with_unknown_language(app, status, warning):
+    app.builder.build_all()
+    result = (app.outdir / 'Python.tex').text(encoding='utf8')
+    print(result)
+    print(status.getvalue())
+    print(warning.getvalue())
+    assert '\\documentclass[letterpaper,10pt,english]{sphinxmanual}' in result
+    assert '\\usepackage{babel}' in result
+    assert '\\usepackage{times}' in result
+    assert '\\usepackage[Sonny]{fncychap}' in result
+    assert ('\\addto\\captionsenglish{\\renewcommand{\\contentsname}{Table of content}}\n'
+            in result)
+    assert '\\addto\\captionsenglish{\\renewcommand{\\figurename}{Fig. }}\n' in result
+    assert '\\addto\\captionsenglish{\\renewcommand{\\tablename}{Table. }}\n' in result
+
+    assert "WARNING: no Babel option known for language 'unknown'" in warning.getvalue()
 
 
 @with_app(buildername='latex')