feathr-ai · xiaoyongzhu · May 18, 2022 · May 8, 2022 · May 15, 2022 · May 15, 2022
diff --git a/feathr_project/feathr/__init__.py b/feathr_project/feathr/__init__.py
@@ -13,3 +13,4 @@
 from .lookup_feature import LookupFeature
 from .aggregation import Aggregation
 from .feathr_configurations import SparkExecutionConfiguration
+from .api.app.core.feathr_api_exception import *
diff --git a/feathr_project/feathr/api/app/core/feathr_api_exception.py b/feathr_project/feathr/api/app/core/feathr_api_exception.py
@@ -1,8 +1,17 @@
-from app.core.error_code import ErrorCode
-
+from feathr.api.app.core.error_code import ErrorCode
 
 class FeathrApiException(Exception):
     def __init__(self,message:str,code:ErrorCode):
         self.code = code
         self.message = message
 
+
+class FeatureNameValidationError(ValueError):
+    """An exception for feature name validation.
+       Feature names must consist of letters, number, or underscores,
+       and cannot begin with a number.
+       Periods are also disallowed, as some compute engines, such as Spark,
+       will consider them as operators in feature name.
+    """
+
+
diff --git a/feathr_project/feathr/feature.py b/feathr_project/feathr/feature.py
@@ -1,13 +1,15 @@
-from abc import ABC, abstractmethod
+import re
 from copy import deepcopy
 from typing import List, Optional, Union, Dict
 
 from jinja2 import Template
 
+from feathr.api.app.core.feathr_api_exception import FeatureNameValidationError
 from feathr.dtype import FeatureType
-from feathr.transformation import ExpressionTransformation, Transformation, WindowAggTransformation
-from feathr.typed_key import DUMMY_KEY, TypedKey
 from feathr.frameconfig import HoconConvertible
+from feathr.transformation import ExpressionTransformation, Transformation
+from feathr.typed_key import DUMMY_KEY, TypedKey
+
 
 class FeatureBase(HoconConvertible):
     """The base class for features
@@ -28,6 +30,7 @@ def __init__(self,
                  key: Optional[Union[TypedKey, List[TypedKey]]] = [DUMMY_KEY],
                  registry_tags: Optional[Dict[str, str]] = None,
                  ):
+        FeatureBase.validate_feature_name(name)
         self.name = name
         self.feature_type = feature_type
         self.registry_tags=registry_tags
@@ -45,6 +48,29 @@ def __init__(self,
         # self.key could be null, when getting features from registry.
         self.key_alias = [k.key_column_alias for k in self.key if k]
 
+    @classmethod
+    def validate_feature_name(cls, feature_name: str) -> bool:
+        """
+        Only alphabet, numbers, and '_' are allowed in the name.
+        It can not start with numbers. Note that '.' is NOT ALLOWED!
+        This is because some compute engines, such as Spark, will consider them as operators in feature name.
+        """
+        if not feature_name:
+            raise FeatureNameValidationError('Feature name rule violation: empty feature name detected')
+
+        feature_validator = re.compile(r"""^              # from the start of the string
+                                           [a-zA-Z_]{1}   # first character can only be a letter or underscore 
+                                           [a-zA-Z0-9_]+  # as many letters, numbers, or underscores as you like  
+                                           $""",          # to the end of the string
+                                       re.X)
+
+        if not feature_validator.match(feature_name):
+            raise FeatureNameValidationError(
+                'Feature name rule violation: only letters, numbers, and underscores are allowed in the name, ' +
+                f'and the name cannot start with a number. name={feature_name}')
+
+        return True
+
     def with_key(self, key_alias: Union[str, List[str]]):
         """Rename the feature key with the alias. This is useful in derived features that depends on
         the same feature with different keys."""

diff --git a/feathr_project/test/test_feature_name_validation.py b/feathr_project/test/test_feature_name_validation.py
@@ -0,0 +1,36 @@
+import string
+
+import pytest
+
+from feathr import FeatureBase, FeatureNameValidationError
+
+
+@pytest.mark.parametrize('bad_feature_name',
+                         [None,
+                          ''])
+def test_feature_name_fails_on_empty_name(bad_feature_name: str):
+    with pytest.raises(FeatureNameValidationError, match="empty feature name"):
+        FeatureBase.validate_feature_name(bad_feature_name)
+
+
+def test_feature_name_fails_on_leading_number():
+    with pytest.raises(FeatureNameValidationError, match="cannot start with a number"):
+        FeatureBase.validate_feature_name("4featurename")
+
+
+def test_feature_name_fails_on_punctuation_chars():
+    for char in set(string.punctuation) - set('_'):
+        with pytest.raises(FeatureNameValidationError,  match="only letters, numbers, and underscores are allowed"):
+            FeatureBase.validate_feature_name(f"feature_{char}_name")
+
+
+@pytest.mark.parametrize('feature_name',
+                         ["feature_name",
+                          "features4lyfe",
+                          "f_4_feature_",
+                          "_leading_underscores_are_ok",
+                          "CapitalizedFeature"
+                          ''])
+def test_feature_name_validates_ok(feature_name: str):
+    assert FeatureBase.validate_feature_name(feature_name)
+