Port readthedocs/readthedocs-build#38 (#4461)

* Port readthedocs/readthedocs-build#38

* Fix test

readthedocs/config/tests/test_config.py

@@ -729,6 +729,26 @@ def test_requirements_file_respects_configuration(tmpdir):
     assert build.python.requirements == 'requirements.txt'
 
 
+def test_requirements_file_is_null(tmpdir):
+    build = get_build_config(
+        {'requirements_file': None},
+        get_env_config(),
+        source_file=str(tmpdir.join('readthedocs.yml')),
+    )
+    build.validate()
+    assert build.requirements_file is None
+
+
+def test_requirements_file_is_blank(tmpdir):
+    build = get_build_config(
+        {'requirements_file': ''},
+        get_env_config(),
+        source_file=str(tmpdir.join('readthedocs.yml')),
+    )
+    build.validate()
+    assert build.requirements_file is None
+
+
 def test_build_validate_calls_all_subvalidators(tmpdir):
     apply_fs(tmpdir, minimal_config)
     build = BuildConfigV1(

readthedocs/config/tests/test_parser.py

@@ -33,6 +33,24 @@ def test_parse_single_config():
     assert config[0]['base'] == 'path'
 
 
+def test_parse_null_value():
+    buf = StringIO(u'base: null')
+    config = parse(buf)
+    assert config[0]['base'] is None
+
+
+def test_parse_empty_value():
+    buf = StringIO(u'base:')
+    config = parse(buf)
+    assert config[0]['base'] is None
+
+
+def test_parse_empty_string_value():
+    buf = StringIO(u'base: ""')
+    config = parse(buf)
+    assert config[0]['base'] == ''
+
+
 def test_parse_empty_list():
     buf = StringIO(u'base: []')
     config = parse(buf)