Added the fix to add missing project length validation.

 Addressing the issue - #4626

sdk/python/feast/repo_config.py

@@ -158,9 +158,9 @@ class RepoConfig(FeastBaseModel):
     """Repo config. Typically loaded from `feature_store.yaml`"""
 
     project: StrictStr
-    """ str: Feast project id. This can be any alphanumeric string up to 16 characters.
+    """ str: This acts as a unique project identifier. This can be any alphanumeric string up to 16 characters and can have '_' but can not start with '_'.
         You can have multiple independent feature repositories deployed to the same cloud
-        provider account, as long as they have different project ids.
+        provider account, as long as they have different project identifier.
     """
 
     provider: StrictStr = "local"

sdk/python/feast/repo_operations.py

@@ -395,7 +395,7 @@ def apply_total(repo_config: RepoConfig, repo_path: Path, skip_source_validation
         store, registry = _get_store_and_registry(repo_config)
         if not is_valid_name(project.name):
             print(
-                f"{project.name} is not valid. Project name should only have "
+                f"{project.name} is not valid. Project name should not be more than 16 characters, should only have "
                 f"alphanumerical values and underscores but not start with an underscore."
             )
             sys.exit(1)
@@ -503,7 +503,11 @@ def init_repo(repo_name: str, template: str):
 
 def is_valid_name(name: str) -> bool:
     """A name should be alphanumeric values and underscores but not start with an underscore"""
-    return not name.startswith("_") and re.compile(r"\W+").search(name) is None
+    return (
+            len(name) <= 16 and  # the name is not greater than 16 characters
+            not name.startswith("_") and  # name does not start with an underscore
+            re.match(r"^[a-zA-Z0-9_]+$", name) is not None  # Ensures it only contains alphanumeric and _
+        )
 
 
 def generate_project_name() -> str:

sdk/python/tests/unit/sdk/python/feast/test_repo_operations_validate_feast_project_name.py

@@ -0,0 +1,25 @@
+from sdk.python.feast.repo_operations import is_valid_name
+
+
+def test_is_valid_name():
+    test_cases = [
+        # Valid project name cases
+        ("valid_name1", True),
+        ("username_1234", True),
+        ("valid123", True),
+        ("1234567890123456", True),
+        ("invalid_name_", True),
+
+        # Invalid project name cases
+        ("_invalidName", False),
+        ("invalid-Name", False),
+        ("too_long_name_123", False),
+        ("invalid name", False),
+        ("invalid@name", False),
+        ("invalid$name", False),
+        ("__", False),
+        ("12345678901234567", False),
+    ]
+
+    for name, expected in test_cases:
+        assert is_valid_name(name) == expected, f"Failed for project invalid name: {name}"