Traitlets unions of callables or values

conda-store-server/conda_store_server/app.py

@@ -12,6 +12,7 @@
     Bool,
     validate,
     TraitError,
+    Union,
 )
 from traitlets.config import LoggingConfigurable
 from sqlalchemy.pool import NullPool
@@ -277,12 +278,19 @@ def _default_celery_results_backend(self):
         config=True,
     )
 
-    default_docker_base_image = Unicode(
-        "registry-1.docker.io/library/debian:sid-slim",
-        help="default base image used for the Dockerized environments. Make sure to have a proper glibc within image.",
+    default_docker_base_image = Union(
+        [Unicode(), Callable()],
+        help="default base image used for the Dockerized environments. Make sure to have a proper glibc within image (highly discourage alpine/musl based images). Can also be callable function which takes the `orm.Build` object as input which has access to all attributes about the build such as install packages, requested packages, name, namespace, etc",
         config=True,
     )
 
+    @default("default_docker_base_image")
+    def _default_docker_base_image(self):
+        def _docker_base_image(build: orm.Build):
+            return "registry-1.docker.io/library/debian:sid-slim"
+
+        return _docker_base_image
+
     validate_specification = Callable(
         conda_store_validate_specification,
         help="callable function taking conda_store and specification as input arguments to apply for validating and modifying a given specification. If there are validation issues with the environment ValueError with message should be raised. If changed you may need to call the default function to preseve many of the trait effects e.g. `c.CondaStore.default_channels` etc",

conda-store-server/conda_store_server/build.py

@@ -291,7 +291,7 @@ def build_conda_docker(conda_store, build):
     precs = precs_from_environment_prefix(conda_prefix, download_dir, user_conda)
     records = fetch_precs(download_dir, precs)
     base_image = conda_store.container_registry.pull_image(
-        conda_store.default_docker_base_image
+        utils.callable_or_value(conda_store.default_docker_base_image, build)
     )
     image = build_docker_environment_image(
         base_image=base_image,

conda-store-server/conda_store_server/server/auth.py

@@ -13,7 +13,7 @@
 from sqlalchemy import or_, and_
 import yarl
 
-from conda_store_server import schema, orm
+from conda_store_server import schema, orm, utils
 from conda_store_server.server import dependencies
 
 
@@ -574,10 +574,7 @@ def _oauth_callback_url(request: Request):
         return _oauth_callback_url
 
     def get_oauth_callback_url(self, request: Request):
-        if callable(self.oauth_callback_url):
-            return self.oauth_callback_url(request)
-        else:
-            return self.oauth_callback_url
+        return utils.callable_or_value(self.oauth_callback_url, request)
 
     login_html = Unicode(
         """

conda-store-server/conda_store_server/utils.py

@@ -72,3 +72,9 @@ def sort_key(v):
 def datastructure_hash(v):
     json_blob = json.dumps(recursive_sort(v))
     return hashlib.sha256(json_blob.encode("utf-8")).hexdigest()
+
+
+def callable_or_value(v, *args, **kwargs):
+    if callable(v):
+        return v(*args, **kwargs)
+    return v

docs/administration.md

@@ -216,9 +216,13 @@ assign to all files and directories in a given built environment. This
 setting is useful if you want to protect environments from
 modification from certain users and groups.
 
-`CondaStore.default_docker_base_image` is the base image to use for
-docker builds of Conda environments. This package at a minimum should
-have the [following packages
+`CondaStore.default_docker_base_image` default base image used for the
+Dockerized environments. Make sure to have a proper glibc within image
+(highly discourage alpine/musl based images). Can also be callable
+function which takes the `orm.Build` object as input which has access
+to all attributes about the build such as installed packages, requested
+packages, name, namespace, etc. This package at a minimum should have
+the [following packages
 installed](https://docs.anaconda.com/anaconda/install/linux/). Often
 times for non-graphic and non-gpu environments glibc is enough. Hence
 the default docker image `library/debian:sid-slim`.