Support per-target Ruby toolchain

ruby/private/binary.bzl

@@ -43,6 +43,10 @@ Supports `$(location)` expansion for targets from `srcs`, `data` and `deps`.
     "env_inherit": attr.string_list(
         doc = "List of environment variable names to be inherited by the test runner.",
     ),
+    "ruby": attr.label(
+        doc = "Override Ruby toolchain to use when running the script.",
+        providers = [platform_common.ToolchainInfo],
+    ),
     "_binary_cmd_tpl": attr.label(
         allow_single_file = True,
         default = "@rules_ruby//ruby/private/binary:binary.cmd.tpl",
@@ -63,6 +67,8 @@ Supports `$(location)` expansion for targets from `srcs`, `data` and `deps`.
 # buildifier: disable=function-docstring
 def generate_rb_binary_script(ctx, binary, bundler = False, args = [], env = {}, java_bin = ""):
     toolchain = ctx.toolchains["@rules_ruby//ruby:toolchain_type"]
+    if ctx.attr.ruby != None:
+        toolchain = ctx.attr.ruby[platform_common.ToolchainInfo]
 
     binary_path = ""
     locate_binary_in_runfiles = ""

ruby/private/bundle_fetch.bzl

@@ -23,6 +23,7 @@ _GEM_INSTALL_BUILD_FRAGMENT = """
 rb_gem_install(
     name = "{name}",
     gem = "{cache_path}/{gem}",
+    ruby = {ruby},
 )
 """
 
@@ -31,6 +32,7 @@ rb_binary(
     name = "{name}",
     main = "{path}/{name}",
     deps = ["//:{repository_name}"],
+    ruby = {ruby},
 )
 """
 
@@ -136,6 +138,7 @@ def _rb_bundle_fetch_impl(repository_ctx):
     gem_fragments = []
     gem_install_fragments = []
     gem_checksums = {}
+    ruby_toolchain_attr = "None" if repository_ctx.attr.ruby == None else '"{}"'.format(repository_ctx.attr.ruby)
     repository_name = _normalize_bzlmod_repository_name(repository_ctx.name)
 
     # Fetch gems and expose them as `rb_gem()` targets.
@@ -164,6 +167,7 @@ def _rb_bundle_fetch_impl(repository_ctx):
             name = gemfile_lock.bundler.full_name,
             gem = gemfile_lock.bundler.filename,
             cache_path = cache_path,
+            ruby = ruby_toolchain_attr,
         ),
     )
 
@@ -178,6 +182,7 @@ def _rb_bundle_fetch_impl(repository_ctx):
                 name = executable,
                 repository_name = repository_name,
                 path = BINSTUBS_LOCATION.partition("/")[-1],
+                ruby = ruby_toolchain_attr,
             ),
         )
     repository_ctx.template(
@@ -203,6 +208,7 @@ def _rb_bundle_fetch_impl(repository_ctx):
             "{gem_fragments}": "".join(gem_fragments),
             "{gem_install_fragments}": "".join(gem_install_fragments),
             "{env}": repr(repository_ctx.attr.env),
+            "{ruby}": ruby_toolchain_attr,
         },
     )
 
@@ -250,6 +256,10 @@ rb_bundle_fetch = repository_rule(
             default = {},
             doc = "SHA-256 checksums for remote gems. Keys are gem names (e.g. foobar-1.2.3), values are SHA-256 checksums.",
         ),
+        "ruby": attr.label(
+            doc = "Override Ruby toolchain to use for installation.",
+            providers = [platform_common.ToolchainInfo],
+        ),
         "_build_tpl": attr.label(
             allow_single_file = True,
             default = "@rules_ruby//:ruby/private/bundle_fetch/BUILD.tpl",

ruby/private/bundle_fetch/BUILD.tpl

@@ -11,6 +11,7 @@ rb_bundle_install(
     gemfile = "{gemfile_path}",
     gemfile_lock = "{gemfile_lock_path}",
     gems = {gems},
+    ruby = {ruby},
 )
 
 {gem_fragments}

ruby/private/bundle_install.bzl

@@ -11,6 +11,8 @@ load(
 
 def _rb_bundle_install_impl(ctx):
     toolchain = ctx.toolchains["@rules_ruby//ruby:toolchain_type"]
+    if ctx.attr.ruby != None:
+        toolchain = ctx.attr.ruby[platform_common.ToolchainInfo]
 
     tools = []
     tools.extend(toolchain.files)
@@ -137,6 +139,10 @@ rb_bundle_install = rule(
         "env": attr.string_dict(
             doc = "Environment variables to use during installation.",
         ),
+        "ruby": attr.label(
+            doc = "Override Ruby toolchain to use when installing the gem.",
+            providers = [platform_common.ToolchainInfo],
+        ),
         "_runfiles_library": attr.label(
             allow_single_file = True,
             default = "@bazel_tools//tools/bash/runfiles",

ruby/private/gem_install.bzl

@@ -12,6 +12,8 @@ def _rb_gem_install_impl(ctx):
     gem = ctx.file.gem
     install_dir = ctx.actions.declare_directory(gem.basename[:-4])
     toolchain = ctx.toolchains["@rules_ruby//ruby:toolchain_type"]
+    if ctx.attr.ruby != None:
+        toolchain = ctx.attr.ruby[platform_common.ToolchainInfo]
 
     env = {}
     env.update(toolchain.env)
@@ -71,6 +73,10 @@ rb_gem_install = rule(
             mandatory = True,
             doc = "Gem file to install.",
         ),
+        "ruby": attr.label(
+            doc = "Override Ruby toolchain to use when installing the gem.",
+            providers = [platform_common.ToolchainInfo],
+        ),
         "_gem_install_cmd_tpl": attr.label(
             allow_single_file = True,
             default = "@rules_ruby//ruby/private/gem_install:gem_install.cmd.tpl",