Expand make variables in env

examples/WORKSPACE.bazel

@@ -35,6 +35,10 @@ load("@rules_foreign_cc_examples_third_party//:repositories.bzl", examples_third
 
 examples_third_party_repositories()
 
+load("@rules_foreign_cc_examples_third_party//:setup.bzl", examples_third_party_setup = "setup")
+
+examples_third_party_setup()
+
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(

examples/third_party/openssl/BUILD.openssl.bazel

@@ -60,7 +60,7 @@ configure_make_variant(
     env = {
         # The Zi flag must be set otherwise OpenSSL fails to build due to missing .pdb files
         "CFLAGS": "-Zi",
-        "PATH": "$(dirname $(execpath @nasm//:nasm)):$PATH",
+        "PATH": "$$(dirname $(execpath @nasm//:nasm)):$$PATH",
         "PERL": "$(execpath @perl//:perl)",
     },
     lib_name = LIB_NAME,
@@ -79,8 +79,13 @@ configure_make(
     configure_in_place = True,
     configure_options = CONFIGURE_OPTIONS,
     env = select({
-        "@platforms//os:macos": {"AR": ""},
-        "//conditions:default": {},
+        "@platforms//os:macos": {
+            "AR": "",
+            "PERL": "$$EXT_BUILD_ROOT$$/$(PERL)",
+        },
+        "//conditions:default": {
+            "PERL": "$$EXT_BUILD_ROOT$$/$(PERL)",
+        },
     }),
     lib_name = LIB_NAME,
     lib_source = ":all_srcs",
@@ -91,6 +96,7 @@ configure_make(
         "libcrypto.a",
     ],
     targets = MAKE_TARGETS,
+    toolchains = ["@rules_perl//:current_toolchain"],
 )
 
 filegroup(

examples/third_party/openssl/openssl_repositories.bzl

@@ -28,7 +28,18 @@ def openssl_repositories():
             "https://www.nasm.us/pub/nasm/releasebuilds/2.15.05/win64/nasm-2.15.05-win64.zip",
         ],
     )
+    maybe(
+        http_archive,
+        name = "rules_perl",
+        sha256 = "55fbe071971772758ad669615fc9aac9b126db6ae45909f0f36de499f6201dd3",
+        strip_prefix = "rules_perl-2f4f36f454375e678e81e5ca465d4d497c5c02da",
+        urls = [
+            "https://github.com/bazelbuild/rules_perl/archive/2f4f36f454375e678e81e5ca465d4d497c5c02da.tar.gz",
+        ],
+    )
 
+    # rules_perl doesn't currently support Windows, so we need to bring along our own Perl.
+    # https://github.com/bazelbuild/rules_perl/issues/30
     maybe(
         http_archive,
         name = "perl",

examples/third_party/openssl/openssl_setup.bzl

@@ -0,0 +1,7 @@
+"""A module initialising the third party dependencies OpenSSL"""
+
+load("@rules_perl//perl:deps.bzl", "perl_register_toolchains", "perl_rules_dependencies")
+
+def openssl_setup():
+    perl_rules_dependencies()
+    perl_register_toolchains()

examples/third_party/setup.bzl

@@ -0,0 +1,6 @@
+"""A centralized module initializing repositories required for third party examples of rules_foreign_cc which require loading from repositories which themselves were loaded in repositories.bzl."""
+
+load("//openssl:openssl_setup.bzl", "openssl_setup")
+
+def setup():
+    openssl_setup()

foreign_cc/built_tools/private/built_tools_framework.bzl

@@ -8,7 +8,7 @@ load("//foreign_cc/private/framework:helpers.bzl", "convert_shell_script", "sheb
 # Common attributes for all built_tool rules
 FOREIGN_CC_BUILT_TOOLS_ATTRS = {
     "env": attr.string_dict(
-        doc = "Environment variables to set during the build.",
+        doc = "Environment variables to set during the build. This attribute is subject to make variable substitution.",
         default = {},
     ),
     "srcs": attr.label(

foreign_cc/cmake.bzl

@@ -143,6 +143,7 @@ load(
     "cc_external_rule_impl",
     "create_attrs",
     "expand_locations",
+    "expand_locations_and_make_variables",
 )
 load("//foreign_cc/private:transitions.bzl", "make_variant")
 load(
@@ -262,7 +263,7 @@ def _create_configure_script(configureParameters):
         root = root,
         no_toolchain_file = no_toolchain_file,
         user_cache = dict(ctx.attr.cache_entries),
-        user_env = expand_locations(ctx, ctx.attr.env, data),
+        user_env = expand_locations_and_make_variables(ctx, "env", data),
         options = attrs.generate_args,
         cmake_commands = cmake_commands,
         cmake_prefix = prefix,

foreign_cc/configure.bzl

@@ -17,6 +17,7 @@ load(
     "cc_external_rule_impl",
     "create_attrs",
     "expand_locations",
+    "expand_locations_and_make_variables",
 )
 load("//foreign_cc/private:transitions.bzl", "make_variant")
 load("//foreign_cc/private/framework:platform.bzl", "os_name")
@@ -74,7 +75,7 @@ def _create_configure_script(configureParameters):
         for arg in ctx.attr.args
     ])
 
-    user_env = expand_locations(ctx, ctx.attr.env, data)
+    user_env = expand_locations_and_make_variables(ctx, "env", data)
 
     make_commands = []
     prefix = "{} ".format(expand_locations(ctx, attrs.tool_prefix, data)) if attrs.tool_prefix else ""

foreign_cc/private/framework.bzl

@@ -103,6 +103,7 @@ CC_EXTERNAL_RULE_ATTRIBUTES = {
             "`$(execpath)` macros may be used to point at files which are listed as `data`, `deps`, or `build_data`, " +
             "but unlike with other rules, these will be replaced with absolute paths to those files, " +
             "because the build does not run in the exec root. " +
+            "This attribute is subject to make variable substitution. " +
             "No other macros are supported." +
             "Variables containing `PATH` (e.g. `PATH`, `LD_LIBRARY_PATH`, `CPATH`) entries will be prepended to the existing variable."
         ),
@@ -306,7 +307,7 @@ def get_env_prelude(ctx, lib_name, data_dependencies, target_root):
         env.update({"PATH": _normalize_path(linker_path) + ":" + env.get("PATH")})
 
     # Add all user defined variables
-    user_vars = expand_locations(ctx, ctx.attr.env, data_dependencies)
+    user_vars = expand_locations_and_make_variables(ctx, "env", data_dependencies)
     env.update(user_vars)
 
     # If user has defined a PATH variable (e.g. PATH, LD_LIBRARY_PATH, CPATH) prepend it to the existing variable
@@ -388,7 +389,7 @@ def cc_external_rule_impl(ctx, attrs):
     installdir_copy = copy_directory(ctx.actions, "$$INSTALLDIR$$", "copy_{}/{}".format(lib_name, lib_name))
     target_root = paths.dirname(installdir_copy.file.dirname)
 
-    data_dependencies = ctx.attr.data + ctx.attr.build_data
+    data_dependencies = ctx.attr.data + ctx.attr.build_data + ctx.attr.toolchains
 
     # Also add legacy dependencies while they're still available
     data_dependencies += ctx.attr.tools_deps + ctx.attr.additional_tools
@@ -915,6 +916,15 @@ def _expand_command_path(binary, path, command):
     else:
         return command
 
+def expand_locations_and_make_variables(ctx, attr_name, data):
+    unexpanded = getattr(ctx.attr, attr_name)
+    location_expanded = expand_locations(ctx, unexpanded, data)
+
+    # Make variable expansion will treat $$ as escaped values for $ and strip the second one.
+    # Double-escape $s which we insert in expand_locations.
+    make_variable_expanded = {k: ctx.expand_make_variables(attr_name, v.replace("$$EXT_BUILD_ROOT$$", "$$$$EXT_BUILD_ROOT$$$$"), {}) for k, v in location_expanded.items()}
+    return make_variable_expanded
+
 def expand_locations(ctx, expandable, data):
     """Expand locations on a dictionary while ensuring `execpath` is always set to an absolute path