Works with Bazel 0.24.1 and Bazel 0.25.2!

WORKSPACE

@@ -3,6 +3,11 @@ workspace(name = "upb")
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+load(":repository_defs.bzl", "bazel_version_repository")
+
+bazel_version_repository(
+    name = "bazel_version"
+)
 
 http_archive(
     name = "lua",

build_defs.bzl

@@ -1,6 +1,8 @@
 
 load("@bazel_skylib//lib:paths.bzl", "paths")
+load("@bazel_skylib//lib:versions.bzl", "versions")
 load("@bazel_tools//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")
+load("@bazel_version//:bazel_version.bzl", "bazel_version")
 
 _shell_find_runfiles = """
   # --- begin runfiles.bash initialization ---
@@ -272,19 +274,42 @@ def filter_none(elems):
 
 # upb_proto_library() rule
 
-def cc_library_func(ctx, name, hdrs, srcs, deps):
-    compilation_contexts = []
-    linking_contexts = []
-    for dep in deps:
-        if CcInfo in dep:
-            linking_contexts.append(dep[CcInfo].linking_context)
-            compilation_contexts.append(dep[CcInfo].compilation_context)
+def cc_library_func(ctx, name, hdrs, srcs, dep_ccinfos):
+    compilation_contexts = [info.compilation_context for info in dep_ccinfos]
+    linking_contexts = [info.linking_context for info in dep_ccinfos]
     toolchain = find_cpp_toolchain(ctx)
     feature_configuration = cc_common.configure_features(
         cc_toolchain = toolchain,
         requested_features = ctx.features,
         unsupported_features = ctx.disabled_features,
     )
+
+    if is_bazel:
+        if bazel_version == "0.24.1":
+            # Compatibility code until gRPC is on 0.25.2 or later.
+            compilation_info = cc_common.compile(
+                ctx = ctx,
+                feature_configuration = feature_configuration,
+                cc_toolchain = toolchain,
+                srcs = srcs,
+                hdrs = hdrs,
+                compilation_contexts = compilation_contexts,
+            )
+            linking_info = cc_common.link(
+                ctx = ctx,
+                feature_configuration = feature_configuration,
+                cc_toolchain = toolchain,
+                cc_compilation_outputs = compilation_info.cc_compilation_outputs,
+                linking_contexts = linking_contexts,
+            )
+            return CcInfo(
+                compilation_context = compilation_info.compilation_context,
+                linking_context = linking_info.linking_context,
+            )
+
+        if not versions.is_at_least("0.25.2", bazel_version):
+            fail("upb requires Bazel >=0.25.2 or 0.24.1")
+
     (compilation_context, compilation_outputs) = cc_common.compile(
         actions = ctx.actions,
         feature_configuration = feature_configuration,
@@ -354,12 +379,14 @@ def _upb_proto_rule_impl(ctx):
 def _upb_proto_aspect_impl(target, ctx):
     proto_info = target[ProtoInfo]
     files = _compile_upb_protos(ctx, proto_info, proto_info.direct_sources, ctx.attr._ext)
+    deps = ctx.rule.attr.deps + [ctx.attr._upb]
+    dep_ccinfos = [dep[CcInfo] for dep in deps if CcInfo in dep]
     cc_info = cc_library_func(
         ctx = ctx,
         name = ctx.rule.attr.name,
         hdrs = files.hdrs,
         srcs = files.srcs,
-        deps = ctx.rule.attr.deps + [ctx.attr._upb],
+        dep_ccinfos = dep_ccinfos,
     )
     return [cc_info]
 

repository_defs.bzl

@@ -0,0 +1,16 @@
+
+# A hacky way to work around the fact that native.bazel_version is only
+# available from WORKSPACE macros, not BUILD macros or rules.
+#
+# Hopefully we can remove this if/when this is fixed:
+#   https://github.com/bazelbuild/bazel/issues/8305
+
+def _impl(repository_ctx):
+    s = "bazel_version = \"" + native.bazel_version + "\""
+    repository_ctx.file("bazel_version.bzl", s)
+    repository_ctx.file("BUILD", "")
+
+bazel_version_repository = repository_rule(
+    implementation=_impl,
+    local=True,
+)

tools/make_cmakelists.py

@@ -175,6 +175,9 @@ class WorkspaceFileFunctions(object):
   def git_repository(self, **kwargs):
     pass
 
+  def bazel_version_repository(self, **kwargs):
+    pass
+
 
 class Converter(object):
   def __init__(self):