chore: Refactor digest targets into a private helper method

oci/defs.bzl

@@ -33,44 +33,53 @@ def _write_nl_seperated_file(name, kind, elems, forwarded_kwargs):
     )
     return label
 
-def oci_image_index(name, **kwargs):
-    """Macro wrapper around [oci_image_index_rule](#oci_image_index_rule).
-
-    Produces a target `[name].digest`, whose default output is a file containing the sha256 digest of the resulting image.
-    This is the same output as for the `oci_image` macro.
-
-    Args:
-        name: name of resulting oci_image_index_rule
-        **kwargs: other named arguments to [oci_image_index_rule](#oci_image_index_rule) and
-            [common rule attributes](https://bazel.build/reference/be/common-definitions#common-attributes).
-    """
-    forwarded_kwargs = propagate_common_rule_attributes(kwargs)
-
-    oci_image_index_rule(
-        name = name,
-        **kwargs
-    )
-
+def _digest(name, **kwargs):
+    # `oci_image_rule` and `oci_image_index_rule` produce a directory as default output.
+    # Label for the [name]/index.json file
     directory_path(
         name = "_{}_index_json".format(name),
         directory = name,
         path = "index.json",
-        **forwarded_kwargs
+        **kwargs
     )
 
     copy_file(
         name = "_{}_index_json_cp".format(name),
         src = "_{}_index_json".format(name),
         out = "_{}_index.json".format(name),
-        **forwarded_kwargs
+        **kwargs
     )
 
+    # Matches the [name].digest target produced by rules_docker container_image
     jq(
         name = name + ".digest",
         args = ["--raw-output"],
         srcs = ["_{}_index.json".format(name)],
         filter = """.manifests[0].digest""",
         out = name + ".json.sha256",  # path chosen to match rules_docker for easy migration
+        **kwargs
+    )
+
+def oci_image_index(name, **kwargs):
+    """Macro wrapper around [oci_image_index_rule](#oci_image_index_rule).
+
+    Produces a target `[name].digest`, whose default output is a file containing the sha256 digest of the resulting image.
+    This is the same output as for the `oci_image` macro.
+
+    Args:
+        name: name of resulting oci_image_index_rule
+        **kwargs: other named arguments to [oci_image_index_rule](#oci_image_index_rule) and
+            [common rule attributes](https://bazel.build/reference/be/common-definitions#common-attributes).
+    """
+    forwarded_kwargs = propagate_common_rule_attributes(kwargs)
+
+    oci_image_index_rule(
+        name = name,
+        **kwargs
+    )
+
+    _digest(
+        name = name,
         **forwarded_kwargs
     )
 
@@ -200,29 +209,8 @@ def oci_image(
         **kwargs
     )
 
-    # `oci_image_rule` produces a directory as default output.
-    # Label for the [name]/index.json file
-    directory_path(
-        name = "_{}_index_json".format(name),
-        directory = name,
-        path = "index.json",
-        **forwarded_kwargs
-    )
-
-    copy_file(
-        name = "_{}_index_json_cp".format(name),
-        src = "_{}_index_json".format(name),
-        out = "_{}_index.json".format(name),
-        **forwarded_kwargs
-    )
-
-    # Matches the [name].digest target produced by rules_docker container_image
-    jq(
-        name = name + ".digest",
-        args = ["--raw-output"],
-        srcs = ["_{}_index.json".format(name)],
-        filter = """.manifests[0].digest""",
-        out = name + ".json.sha256",  # path chosen to match rules_docker for easy migration
+    _digest(
+        name = name,
         **forwarded_kwargs
     )