fix: don't overwrite user base image

src/bentoml/_internal/bento/build_config.py

@@ -149,13 +149,13 @@ class DockerOptions:
     # always omit config values in case of default values got changed in future BentoML releases
     __omit_if_default__ = False
 
-    distro: str = attr.field(
+    distro: t.Optional[str] = attr.field(
         default=None,
         validator=attr.validators.optional(
             attr.validators.in_(CONTAINER_SUPPORTED_DISTROS)
         ),
     )
-    python_version: str = attr.field(
+    python_version: t.Optional[str] = attr.field(
         converter=_convert_python_version,
         default=None,
         validator=attr.validators.optional(

src/bentoml/_internal/container/generate.py

@@ -58,24 +58,27 @@ def get_templates_variables(
     """
     Returns a dictionary of variables to be used in BentoML base templates.
     """
-    spec = DistroSpec.from_options(docker, conda)
     conda_python_version = conda.get_python_version(bento_fs)
     if conda_python_version is None:
         conda_python_version = docker.python_version
 
-    python_version = docker.python_version
-    if docker.distro in ("ubi8"):
-        # ubi8 base images uses "py38" instead of "py3.8" in its image tag
-        python_version = python_version.replace(".", "")
-    base_image = spec.image.format(spec_version=python_version)
-    if docker.cuda_version is not None:
-        base_image = spec.image.format(spec_version=docker.cuda_version)
     if docker.base_image is not None:
         base_image = docker.base_image
         logger.info(
             "BentoML will not install Python to custom base images; ensure the base image '%s' has Python installed.",
             base_image,
         )
+    else:
+        spec = DistroSpec.from_options(docker, conda)
+        python_version = docker.python_version
+        assert docker.distro is not None and python_version is not None
+        if docker.distro in ("ubi8"):
+            # ubi8 base images uses "py38" instead of "py3.8" in its image tag
+            python_version = python_version.replace(".", "")
+        base_image = spec.image.format(spec_version=python_version)
+        if docker.cuda_version is not None:
+            base_image = spec.image.format(spec_version=docker.cuda_version)
+
     # bento__env
     default_env = {
         "uid_gid": BENTO_UID_GID,

src/bentoml/_internal/server/grpc/servicer/v1/__init__.py

@@ -7,6 +7,7 @@
 from typing import TYPE_CHECKING
 
 import anyio
+
 from .....utils import LazyLoader
 from ......exceptions import InvalidArgument
 from ......exceptions import BentoMLException
@@ -22,6 +23,7 @@
 
     import grpc
     from google.protobuf import struct_pb2
+
     from ......grpc.v1 import service_pb2 as pb
     from ......grpc.v1 import service_pb2_grpc as services
     from ......grpc.types import BentoServicerContext