[BUG] Use Daft s3 credentials chain for deltalake reads (#2486)

**Before:** Without user intervention (by passing in explicit
credentials), Daft would pass in `None` for credentials when
instantiating the `DeltaTable` objects, causing auth issues with S3.

**After:** We detect and special-case when there are no credentials
being passed in, and try to use Daft's credentials chain to override the
empty credentials before instantiating the `DeltaTable`

<img width="727" alt="image"
src="https://github.com/Eventual-Inc/Daft/assets/17691182/a45ac789-7f4d-4691-9f88-9b26089aeba6">

---------

Co-authored-by: Jay Chia <[email protected]@users.noreply.github.com>

daft/delta_lake/delta_lake_scan.py

@@ -7,10 +7,12 @@
 from deltalake.table import DeltaTable
 
 import daft
+import daft.exceptions
 from daft.daft import (
     FileFormatConfig,
     ParquetSourceConfig,
     Pushdowns,
+    S3Config,
     ScanTask,
     StorageConfig,
 )
@@ -24,8 +26,44 @@
 class DeltaLakeScanOperator(ScanOperator):
     def __init__(self, table_uri: str, storage_config: StorageConfig) -> None:
         super().__init__()
-        storage_options = io_config_to_storage_options(storage_config.config.io_config, table_uri)
-        self._table = DeltaTable(table_uri, storage_options=storage_options)
+
+        # Unfortunately delta-rs doesn't do very good inference of credentials for S3. Thus the current Daft behavior of passing
+        # in `None` for credentials will cause issues when instantiating the DeltaTable without credentials.
+        #
+        # Thus, if we don't detect any credentials being available, we attempt to detect it from the environment using our Daft credentials chain.
+        #
+        # See: https://github.com/delta-io/delta-rs/issues/2117
+        deltalake_sdk_io_config = storage_config.config.io_config
+        if any([deltalake_sdk_io_config.s3.key_id is None, deltalake_sdk_io_config.s3.region_name is None]):
+            try:
+                s3_config_from_env = S3Config.from_env()
+            # Sometimes S3Config.from_env throws an error, for example on CI machines with weird metadata servers.
+            except daft.exceptions.DaftCoreException:
+                pass
+            else:
+                if (
+                    deltalake_sdk_io_config.s3.key_id is None
+                    and deltalake_sdk_io_config.s3.access_key is None
+                    and deltalake_sdk_io_config.s3.session_token is None
+                ):
+                    deltalake_sdk_io_config = deltalake_sdk_io_config.replace(
+                        s3=deltalake_sdk_io_config.s3.replace(
+                            key_id=s3_config_from_env.key_id,
+                            access_key=s3_config_from_env.access_key,
+                            session_token=s3_config_from_env.session_token,
+                        )
+                    )
+                if deltalake_sdk_io_config.s3.region_name is None:
+                    deltalake_sdk_io_config = deltalake_sdk_io_config.replace(
+                        s3=deltalake_sdk_io_config.s3.replace(
+                            region_name=s3_config_from_env.region_name,
+                        )
+                    )
+
+        self._table = DeltaTable(
+            table_uri, storage_options=io_config_to_storage_options(deltalake_sdk_io_config, table_uri)
+        )
+
         self._storage_config = storage_config
         self._schema = Schema.from_pyarrow_schema(self._table.schema().to_pyarrow())
         partition_columns = set(self._table.metadata().partition_columns)