feat: implement tars symlinks

MODULE.bazel

@@ -9,6 +9,7 @@ module(
 bazel_dep(name = "aspect_bazel_lib", version = "2.7.2")
 bazel_dep(name = "bazel_skylib", version = "1.5.0")
 bazel_dep(name = "platforms", version = "0.0.8")
+bazel_dep(name = "bazel_features", version = "1.10.0")
 
 oci = use_extension("//oci:extensions.bzl", "oci")
 oci.toolchains()

oci/dependencies.bzl

@@ -26,3 +26,10 @@ def rules_oci_dependencies():
         strip_prefix = "bazel-lib-2.7.2",
         url = "https://github.com/aspect-build/bazel-lib/releases/download/v2.7.2/bazel-lib-v2.7.2.tar.gz",
     )
+
+    http_archive(
+        name = "bazel_features",
+        sha256 = "95fb3cfd11466b4cad6565e3647a76f89886d875556a4b827c021525cb2482bb",
+        strip_prefix = "bazel_features-1.10.0",
+        url = "https://github.com/bazel-contrib/bazel_features/releases/download/v1.10.0/bazel_features-v1.10.0.tar.gz",
+    )

oci/private/image.bzl

@@ -1,5 +1,6 @@
 "Implementation details for image rule"
 
+load("@bazel_features//:features.bzl", "bazel_features")
 load("//oci/private:util.bzl", "util")
 
 _ACCEPTED_TAR_EXTENSIONS = [
@@ -139,6 +140,8 @@ def _oci_image_impl(ctx):
 
     output = ctx.actions.declare_directory(ctx.label.name)
 
+    use_symlinks = bazel_features.rules.permits_treeartifact_uplevel_symlinks
+
     # create the image builder
     builder = ctx.actions.declare_file("image_%s.sh" % ctx.label.name)
     ctx.actions.expand_template(
@@ -150,10 +153,12 @@ def _oci_image_impl(ctx):
             "{{jq_path}}": jq.jqinfo.bin.dirname,
             "{{coreutils_path}}": coreutils.coreutils_info.bin.dirname,
             "{{output}}": output.path,
+            "{{treeartifact_symlinks}}": str(int(use_symlinks)),
         },
     )
 
-    inputs = [builder] + ctx.files.tars
+    inputs = [builder]
+    transitive_inputs = []
 
     args = ctx.actions.args()
 
@@ -165,6 +170,12 @@ def _oci_image_impl(ctx):
         # create a scratch base image with given os/arch[/variant]
         args.add(_platform_str(ctx.attr.os, ctx.attr.architecture, ctx.attr.variant), format = "--scratch=%s")
 
+    # If tree artifact symlinks are supported just add tars into runfiles.
+    if use_symlinks:
+        transitive_inputs = transitive_inputs + ctx.files.tars
+    else:
+        inputs = inputs + ctx.files.tars
+
     # add layers
     for (i, layer) in enumerate(ctx.files.tars):
         descriptor = _calculate_descriptor(ctx, i, layer, zstd, jq, coreutils, regctl)
@@ -233,6 +244,7 @@ def _oci_image_impl(ctx):
     return [
         DefaultInfo(
             files = depset([output]),
+            runfiles = ctx.runfiles(transitive_inputs),
         ),
     ]
 

oci/private/image.sh

@@ -7,6 +7,7 @@ PATH="{{regctl_path}}:$PATH"
 PATH="{{coreutils_path}}:$PATH"
 
 # Constants
+readonly USE_TREEARTIFACT_SYMLINKS="{{treeartifact_symlinks}}"
 readonly OUTPUT="{{output}}"
 readonly REF="ocidir://$OUTPUT:intermediate"
 # shellcheck disable=SC2016
@@ -96,7 +97,12 @@ function add_layer() {
   local digest_path= 
   digest_path="$(jq -r '.digest | sub(":"; "/")' <<< "$desc")"
 
-  coreutils cat "$path" > "$OUTPUT/blobs/$digest_path"
+  if [[ "$USE_TREEARTIFACT_SYMLINKS" == "1" ]]; then
+    relative=$(coreutils realpath --relative-to="$OUTPUT/blobs/sha256" "$path" --no-symlinks)
+    coreutils ln -s "$relative" "$OUTPUT/blobs/$digest_path"
+  else
+    coreutils cat "$path" > "$OUTPUT/blobs/$digest_path"
+  fi
 }
 
 CONFIG="{}"

oci/repositories.bzl

@@ -8,6 +8,7 @@ load(
     "register_tar_toolchains",
     "register_zstd_toolchains",
 )
+load("@bazel_features//:deps.bzl", "bazel_features_deps")
 load("//oci/private:toolchains_repo.bzl", "PLATFORMS", "toolchains_repo")
 load("//oci/private:versions.bzl", "CRANE_VERSIONS", "REGCTL_VERSIONS")
 
@@ -100,6 +101,7 @@ def oci_register_toolchains(name, register = True):
         register: whether to call through to native.register_toolchains.
             Should be True for WORKSPACE users, but false when used under bzlmod extension
     """
+    bazel_features_deps()
     register_jq_toolchains(register = register)
     register_tar_toolchains(register = register)
     register_coreutils_toolchains(register = register)