load("//go/private:sdk.bzl", "detect_host_platform", "go_download_sdk_rule", "go_host_sdk_rule", "go_multiple_toolchains") load("//go/private:repositories.bzl", "go_rules_dependencies") def host_compatible_toolchain_impl(ctx): ctx.file("BUILD.bazel") ctx.file("defs.bzl", content = """ HOST_COMPATIBLE_SDK = Label({}) """.format(repr(ctx.attr.toolchain))) host_compatible_toolchain = repository_rule( implementation = host_compatible_toolchain_impl, attrs = { # We cannot use attr.label for the `toolchain` attribute since the module extension cannot # refer to the repositories it creates by their apparent repository names. "toolchain": attr.string( doc = "The apparent label of a `ROOT` file in the repository of a host compatible toolchain created by the `go_sdk` extension", mandatory = True, ), }, doc = "An external repository to expose the first host compatible toolchain", ) _download_tag = tag_class( attrs = { "name": attr.string(), "goos": attr.string(), "goarch": attr.string(), "sdks": attr.string_list_dict(), "urls": attr.string_list(default = ["https://dl.google.com/go/{}"]), "version": attr.string(), "strip_prefix": attr.string(default = "go"), }, ) _host_tag = tag_class( attrs = { "name": attr.string(), "version": attr.string(), }, ) # This limit can be increased essentially arbitrarily, but doing so will cause a rebuild of all # targets using any of these toolchains due to the changed repository name. _MAX_NUM_TOOLCHAINS = 9999 _TOOLCHAIN_INDEX_PAD_LENGTH = len(str(_MAX_NUM_TOOLCHAINS)) def _go_sdk_impl(ctx): multi_version_module = {} for module in ctx.modules: if module.name in multi_version_module: multi_version_module[module.name] = True else: multi_version_module[module.name] = False # We remember the first host compatible toolchain declared by the download and host tags. # The order follows bazel's iteration over modules (the toolchains declared by the root module are considered first). # We know that at least `go_default_sdk` (which is declared by the `rules_go` module itself) is host compatible. first_host_compatible_toolchain = None host_detected_goos, host_detected_goarch = detect_host_platform(ctx) toolchains = [] for module in ctx.modules: for index, download_tag in enumerate(module.tags.download): # SDKs without an explicit version are fetched even when not selected by toolchain # resolution. This is acceptable if brought in by the root module, but transitive # dependencies should not slow down the build in this way. if not module.is_root and not download_tag.version: fail("go_sdk.download: version must be specified in non-root module " + module.name) # SDKs with an explicit name are at risk of colliding with those from other modules. # This is acceptable if brought in by the root module as the user is responsible for any # conflicts that arise. rules_go itself provides "go_default_sdk", which is used by # Gazelle to bootstrap itself. # TODO(https://github.com/bazelbuild/bazel-gazelle/issues/1469): Investigate whether # Gazelle can use the first user-defined SDK instead to prevent unnecessary downloads. if (not module.is_root and not module.name == "rules_go") and download_tag.name: fail("go_sdk.download: name must not be specified in non-root module " + module.name) name = download_tag.name or _default_go_sdk_name( module = module, multi_version = multi_version_module[module.name], tag_type = "download", index = index, ) go_download_sdk_rule( name = name, goos = download_tag.goos, goarch = download_tag.goarch, sdks = download_tag.sdks, urls = download_tag.urls, version = download_tag.version, ) if (not download_tag.goos or download_tag.goos == host_detected_goos) and (not download_tag.goarch or download_tag.goarch == host_detected_goarch): first_host_compatible_toolchain = first_host_compatible_toolchain or "@{}//:ROOT".format(name) toolchains.append(struct( goos = download_tag.goos, goarch = download_tag.goarch, sdk_repo = name, sdk_type = "remote", sdk_version = download_tag.version, )) for index, host_tag in enumerate(module.tags.host): # Dependencies can rely on rules_go providing a default remote SDK. They can also # configure a specific version of the SDK to use. However, they should not add a # dependency on the host's Go SDK. if not module.is_root: fail("go_sdk.host: cannot be used in non-root module " + module.name) name = host_tag.name or _default_go_sdk_name( module = module, multi_version = multi_version_module[module.name], tag_type = "host", index = index, ) go_host_sdk_rule( name = name, version = host_tag.version, ) toolchains.append(struct( goos = "", goarch = "", sdk_repo = name, sdk_type = "host", sdk_version = host_tag.version, )) first_host_compatible_toolchain = first_host_compatible_toolchain or "@{}//:ROOT".format(name) host_compatible_toolchain(name = "go_host_compatible_sdk_label", toolchain = first_host_compatible_toolchain) if len(toolchains) > _MAX_NUM_TOOLCHAINS: fail("more than {} go_sdk tags are not supported".format(_MAX_NUM_TOOLCHAINS)) # Toolchains in a BUILD file are registered in the order given by name, not in the order they # are declared: # https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/packages/Package.java;drc=8e41dce65b97a3d466d6b1e65005abc52a07b90b;l=156 # We pad with an index that lexicographically sorts in the same order as if these toolchains # were registered using register_toolchains in their MODULE.bazel files. go_multiple_toolchains( name = "go_toolchains", prefixes = [ _toolchain_prefix(index, toolchain.sdk_repo) for index, toolchain in enumerate(toolchains) ], geese = [toolchain.goos for toolchain in toolchains], goarchs = [toolchain.goarch for toolchain in toolchains], sdk_repos = [toolchain.sdk_repo for toolchain in toolchains], sdk_types = [toolchain.sdk_type for toolchain in toolchains], sdk_versions = [toolchain.sdk_version for toolchain in toolchains], ) def _default_go_sdk_name(*, module, multi_version, tag_type, index): # Keep the version out of the repository name if possible to prevent unnecessary rebuilds when # it changes. return "{name}_{version}_{tag_type}_{index}".format( name = module.name, version = module.version if multi_version else "", tag_type = tag_type, index = index, ) def _toolchain_prefix(index, name): """Prefixes the given name with the index, padded with zeros to ensure lexicographic sorting. Examples: _toolchain_prefix( 2, "foo") == "_0002_foo_" _toolchain_prefix(2000, "foo") == "_2000_foo_" """ return "_{}_{}_".format(_left_pad_zero(index, _TOOLCHAIN_INDEX_PAD_LENGTH), name) def _left_pad_zero(index, length): if index < 0: fail("index must be non-negative") return ("0" * length + str(index))[-length:] go_sdk = module_extension( implementation = _go_sdk_impl, tag_classes = { "download": _download_tag, "host": _host_tag, }, ) def _non_module_dependencies_impl(_ctx): go_rules_dependencies(force = True) non_module_dependencies = module_extension( implementation = _non_module_dependencies_impl, )