Add nicer validation for repo config

sdk/python/docs/index.rst

@@ -41,3 +41,10 @@ Constants
 .. automodule:: feast.constants
     :members:
     :exclude-members: AuthProvider, ConfigMeta
+
+Config
+==================
+
+.. automodule:: feast.repo_config
+    :members:
+    :exclude-members: load_repo_config

sdk/python/feast/repo_config.py

@@ -3,29 +3,98 @@
 
 import yaml
 from bindr import bind
+from jsonschema import ValidationError, validate
 
 
 class LocalOnlineStoreConfig(NamedTuple):
+    """ Online store config for local (SQLite-based) online store """
     path: str
+    """ str: Path to sqlite db """
 
 
 class DatastoreOnlineStoreConfig(NamedTuple):
+    """ Online store config for GCP Datastore """
     project_id: str
+    """ str: GCP Project Id """
 
 
 class OnlineStoreConfig(NamedTuple):
     datastore: Optional[DatastoreOnlineStoreConfig] = None
+    """ DatastoreOnlineStoreConfig: Optional DatastoreConfig """
     local: Optional[LocalOnlineStoreConfig] = None
+    """ LocalOnlineStoreConfig: Optional local online store config """
 
 
 class RepoConfig(NamedTuple):
+    """ Repo config. Typically loaded from `feature_store.yaml` """
     metadata_store: str
+    """ str: Path to metadata store. Can be a local path, or remote object storage path """
     project: str
+    """ str: Feast project id. This can be any alphanumeric string up to 16 characters. """
     provider: str
+    """ str: local or gcp """
     online_store: OnlineStoreConfig
+    """ OnlineStoreConfig: Online store configuration (optional depending on provider) """
+
+
+# This is the JSON Schema for config validation. We use this to have nice detailed error messages
+# for config validation, something that bindr unfortunately doesn't provide out of the box.
+#
+# The schema should match the namedtuple structure above. It could technically even be inferred from
+# the types above automatically; but for now we choose a more tedious but less magic path of
+# providing the schema manually.
+
+config_schema = {
+    "type": "object",
+    "properties": {
+        "project": {"type": "string"},
+        "metadata_store": {"type": "string"},
+        "provider": {"type": "string"},
+        "online_store": {
+            "type": "object",
+            "properties": {
+                "local": {
+                    "type": "object",
+                    "properties": {"path": {"type": "string"}},
+                    "additionalProperties": False,
+                },
+                "datastore": {
+                    "type": "object",
+                    "properties": {"project_id": {"type": "string"}},
+                    "additionalProperties": False,
+                },
+            },
+            "additionalProperties": False,
+        },
+    },
+    "required": ["project"],
+    "additionalProperties": False,
+}
+
+
+class FeastConfigError(Exception):
+    def __init__(self, error_message, error_path, config_path):
+        self._error_message = error_message
+        self._error_path = error_path
+        self._config_path = config_path
+        super().__init__(self._error_message)
+
+    def __str__(self) -> str:
+        if self._error_path:
+            return f'{self._error_message} under {"->".join(self._error_path)} in {self._config_path}'
+        else:
+            return f"{self._error_message} in {self._config_path}"
+
+    def __repr__(self) -> str:
+        return f"FeastConfigError({repr(self._error_message)}, {repr(self._error_path)}, {repr(self._config_path)})"
 
 
 def load_repo_config(repo_path: Path) -> RepoConfig:
-    with open(repo_path / "feature_store.yaml") as f:
+    config_path = repo_path / "feature_store.yaml"
+    with open(config_path) as f:
         raw_config = yaml.safe_load(f)
-        return bind(RepoConfig, raw_config)
+        try:
+            validate(raw_config, config_schema)
+            return bind(RepoConfig, raw_config)
+        except ValidationError as e:
+            raise FeastConfigError(e.message, e.absolute_path, config_path)

sdk/python/setup.py

@@ -48,6 +48,7 @@
     "kubernetes==12.0.*",
     "bindr",
     "mmh3",
+    "jsonschema",
 ]
 
 # README file from Feast repo root directory

sdk/python/tests/test_repo_config.py

@@ -0,0 +1,88 @@
+import re
+import tempfile
+from pathlib import Path
+from textwrap import dedent
+from typing import Optional
+
+from feast.repo_config import FeastConfigError, load_repo_config
+
+
+class TestRepoConfig:
+    def _test_config(self, config_text, expect_error: Optional[str]):
+        """
+        Try loading a repo config and check raised error against a regex.
+        """
+        with tempfile.TemporaryDirectory() as repo_dir_name:
+
+            repo_path = Path(repo_dir_name)
+
+            repo_config = repo_path / "feature_store.yaml"
+
+            repo_config.write_text(config_text)
+            error = None
+            try:
+                load_repo_config(repo_path)
+            except FeastConfigError as e:
+                error = e
+
+            if expect_error is not None:
+                assert re.search(expect_error, str(error)) is not None
+            else:
+                assert error is None
+
+    def test_basic(self) -> None:
+        self._test_config(
+            dedent(
+                """
+            project: foo
+            metadata_store: "metadata.db"
+            provider: local
+            online_store:
+                local:
+                    path: "online_store.db"
+            """
+            ),
+            expect_error=None,
+        )
+
+        self._test_config(
+            dedent(
+                """
+            project: foo
+            metadata_store: "metadata.db"
+            provider: local
+            online_store:
+                local:
+                    that_field_should_not_be_here: yes
+                    path: "online_store.db"
+            """
+            ),
+            expect_error=r"'that_field_should_not_be_here' was unexpected.*online_store->local",
+        )
+
+        self._test_config(
+            dedent(
+                """
+            project: foo
+            metadata_store: "metadata.db"
+            provider: local
+            online_store:
+                local:
+                    path: 100500
+            """
+            ),
+            expect_error=r"100500 is not of type 'string'",
+        )
+
+        self._test_config(
+            dedent(
+                """
+            metadata_store: "metadata.db"
+            provider: local
+            online_store:
+                local:
+                    path: foo
+            """
+            ),
+            expect_error=r"'project' is a required property",
+        )