Add Better error message for lists in config file

readthedocs/config/config.py

@@ -110,16 +110,24 @@ class InvalidConfig(ConfigError):
     message_template = 'Invalid "{key}": {error}'
 
     def __init__(self, key, code, error_message, source_file=None):
-        self.key = key
+        self.key = self._get_display_key(key)
         self.code = code
         self.source_file = source_file
         message = self.message_template.format(
-            key=key,
+            key=self.key,
             code=code,
             error=error_message,
         )
         super().__init__(message, code=code)
 
+    @staticmethod
+    def _get_display_key(key):
+        # Checks for patterns similar to `python.install.0.requirements`
+        # if matched change to `python.install[0].requirements` using backreference.
+        return re.sub(
+            r'^(python\.install)(\.)(\d+)(\.\w+)$', r'\1[\3]\4', key
+        )
+
 
 class BuildConfigBase:
 

readthedocs/config/tests/test_config.py

@@ -1062,7 +1062,7 @@ def test_python_install_method_check_invalid(self, value, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.method'
+        assert excinfo.value.key == 'python.install[0].method'
 
     def test_python_install_requirements_check_valid(self, tmpdir):
         apply_fs(tmpdir, {'requirements.txt': ''})
@@ -1096,7 +1096,24 @@ def test_python_install_requirements_does_not_allow_null(self, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.requirements'
+        assert excinfo.value.key == 'python.install[0].requirements'
+
+    def test_python_install_requirements_error_msg(self, tmpdir):
+        build = self.get_build_config(
+            {
+                'python': {
+                    'install': [{
+                        'path': '.',
+                        'requirements': None,
+                    }],
+                },
+            },
+            source_file=str(tmpdir.join('readthedocs.yml')),
+        )
+        with raises(InvalidConfig) as excinfo:
+            build.validate()
+
+        assert str(excinfo.value) == 'Invalid "python.install[0].requirements": expected string'
 
     def test_python_install_requirements_does_not_allow_empty_string(self, tmpdir):
         build = self.get_build_config(
@@ -1112,7 +1129,7 @@ def test_python_install_requirements_does_not_allow_empty_string(self, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.requirements'
+        assert excinfo.value.key == 'python.install[0].requirements'
 
     def test_python_install_requirements_ignores_default(self, tmpdir):
         apply_fs(tmpdir, {'requirements.txt': ''})
@@ -1157,7 +1174,7 @@ def test_python_install_requirements_check_invalid_types(self, value, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.requirements'
+        assert excinfo.value.key == 'python.install[0].requirements'
 
     def test_python_install_path_is_required(self, tmpdir):
         build = self.get_build_config(
@@ -1307,7 +1324,7 @@ def test_python_install_extra_requirements_and_setuptools(self, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.extra_requirements'
+        assert excinfo.value.key == 'python.install[0].extra_requirements'
 
     @pytest.mark.parametrize('value', [2, 'invalid', {}, '', None])
     def test_python_install_extra_requirements_check_type(self, value, tmpdir):
@@ -1325,7 +1342,7 @@ def test_python_install_extra_requirements_check_type(self, value, tmpdir):
         )
         with raises(InvalidConfig) as excinfo:
             build.validate()
-        assert excinfo.value.key == 'python.install.0.extra_requirements'
+        assert excinfo.value.key == 'python.install[0].extra_requirements'
 
     def test_python_install_extra_requirements_allow_empty(self, tmpdir):
         build = self.get_build_config(
@@ -1852,7 +1869,7 @@ def test_submodules_recursive_explicit_default(self):
                     }]
                 }
             },
-            'python.install.1.invalid'
+            'python.install[1].invalid'
         )
     ])
     def test_strict_validation(self, value, key):