[ABLD-395] Framework to create toolchains for OS provided tools

MODULE.bazel

@@ -127,6 +127,22 @@ archive_override(
     urls = ["https://github.com/bazel-contrib/toolchains_llvm/archive/ffe407ca2423f4d171b7a0f3897c23bbb7e40310.tar.gz"],
 )
 
+#################################
+## Tools that ship with the OS ##
+#################################
+
+find_macos_codesign = use_extension("//bazel/toolchains/codesign:configure.bzl", "find_macos_codesign", dev_dependency = True)
+use_repo(find_macos_codesign, "macos_codesign")
+
+find_macos_pkgbuild = use_extension("//bazel/toolchains/pkgbuild:configure.bzl", "find_macos_pkgbuild", dev_dependency = True)
+use_repo(find_macos_pkgbuild, "macos_pkgbuild")
+
+register_toolchains(
+    "@macos_codesign//:all",
+    "@macos_pkgbuild//:all",
+    dev_dependency = True,
+)
+
 #########################
 ## Prebuilt binaries   ##
 #########################

bazel/toolchains/codesign/BUILD.bazel

@@ -0,0 +1,9 @@
+"""toolchain to wrap the codesign binary.
+
+Type: @codesign//:codesign_toolchain_type
+
+Toolchains:
+- @codesign//:codesign_toolchain: provides the tool
+- @codesign//:codesign_missing_toolchain: provides a fallback toolchain for
+  exec platforms where codesign might not be available.
+"""

bazel/toolchains/codesign/configure.bzl

@@ -0,0 +1,12 @@
+"""Repository rule to autoconfigure a toolchain using the system codesign."""
+
+load("//bazel/toolchains/common:defs.bzl", "make_repo_builder")
+
+# This must match the name used by register_toolchains in consuming MODULE.bazel files.
+NAME = "macos_codesign"
+
+build_repo_for_toolchain = make_repo_builder(name = NAME)
+
+find_macos_codesign = module_extension(
+    implementation = lambda ctx: build_repo_for_toolchain(name = NAME),
+)

bazel/toolchains/common/BUILD.bazel

@@ -0,0 +1,12 @@
+# //bazel/toolchains.
+
+package(default_visibility = ["//visibility:private"])
+
+filegroup(
+    name = "common",
+    srcs = [
+        "toolchain_BUILD.tpl",
+        "toolchain_defs.bzl.tpl",
+    ],
+    visibility = ["//bazel/toolchains:__subpackages__"],
+)

bazel/toolchains/common/defs.bzl

@@ -0,0 +1,56 @@
+"""Utilitites for creating toolchains to wrap system provided tools."""
+
+def write_toolchain_repo(rctx, tool_name, tool_path, tool_version = "<unknown>"):
+    if not tool_path:
+        tool_path = ""
+    rctx.template(
+        "BUILD",
+        Label("@@//bazel/toolchains/common:toolchain_BUILD.tpl"),
+        substitutions = {
+            "{GENERATOR}": "@@//bazel/toolchains/{tool_name}/{tool_name}_configure.bzl%find_system_{tool_name}".format(
+                tool_name = tool_name,
+            ),
+            "{TOOL_NAME}": tool_name,
+            "{TOOL_PATH}": str(tool_path),
+            "{TOOL_VERSION}": tool_version,
+        },
+        executable = False,
+    )
+    rctx.template(
+        "defs.bzl",
+        Label("@@//bazel/toolchains/common:toolchain_defs.bzl.tpl"),
+        substitutions = {
+            "{GENERATOR}": "@@//bazel/toolchains/{tool_name}/{tool_name}_configure.bzl%find_system_{tool_name}".format(
+                tool_name = tool_name,
+            ),
+            "{TOOL_NAME}": tool_name,
+        },
+        executable = False,
+    )
+
+def _default_repo_builder_impl(rctx):
+    tool_name = rctx.original_name
+    tool_path = rctx.which(tool_name)
+    if rctx.attr.verbose:
+        if tool_path:
+            print("Found %s at '%s'" % (tool_name, tool_path))  # buildifier: disable=print
+        else:
+            print("No system %s found." % tool_name)  # buildifier: disable=print
+    write_toolchain_repo(
+        rctx = rctx,
+        tool_name = tool_name,
+        tool_path = tool_path,
+    )
+
+def make_repo_builder(name, impl = _default_repo_builder_impl):
+    return repository_rule(
+        implementation = impl,
+        doc = """Create a repository that defines an {name} toolchain based on the system {name}.""".format(name = name),
+        local = True,
+        environ = ["PATH"],
+        attrs = {
+            "verbose": attr.bool(
+                doc = "If true, print status messages.",
+            ),
+        },
+    )

bazel/toolchains/common/toolchain_BUILD.tpl

@@ -0,0 +1,49 @@
+# This content is generated by {GENERATOR}
+load(":defs.bzl", "is_{TOOL_NAME}_available", "{TOOL_NAME}_toolchain")
+
+toolchain_type(
+    name = "{TOOL_NAME}_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+{TOOL_NAME}_toolchain(
+    name = "{TOOL_NAME}_auto",
+    path = "{TOOL_PATH}",
+    version = "{TOOL_VERSION}",
+)
+
+toolchain(
+    name = "{TOOL_NAME}_toolchain",
+    toolchain = ":{TOOL_NAME}_auto",
+    toolchain_type = ":{TOOL_NAME}_toolchain_type",
+)
+
+# {TOOL_NAME}_missing_toolchain provides a fallback toolchain so that toolchain
+# resolution can succeed even on platforms that do not have that tool.
+# If this toolchain is selected, the constraint ":have_{TOOL_NAME}" will not be satistifed,
+# so that can be used with with exec_compatible_with clauses.
+{TOOL_NAME}_toolchain(
+    name = "no_{TOOL_NAME}",
+)
+
+toolchain(
+    name = "zzz_{TOOL_NAME}_missing_toolchain",  # keep name lexicographically last
+    toolchain = ":no_{TOOL_NAME}",
+    toolchain_type = ":{TOOL_NAME}_toolchain_type",
+)
+
+# Expose the availability of an actual otool as a feature flag, so we can
+# create a config_setting from it.
+is_{TOOL_NAME}_available(
+    name = "is_{TOOL_NAME}_available",
+)
+
+# Expose the availability of the toolchain as a config_setting, so we can
+# select() on it.
+config_setting(
+    name = "have_{TOOL_NAME}",
+    flag_values = {
+        ":is_{TOOL_NAME}_available": "1",
+    },
+    visibility = ["//visibility:public"],
+)

bazel/toolchains/common/toolchain_defs.bzl.tpl

@@ -0,0 +1,51 @@
+"""toolchain to provide the {TOOL_NAME} binary."""
+
+load("@@//bazel/toolchains:toolchain_info.bzl", "ToolInfo")
+
+def _{TOOL_NAME}_toolchain_impl(ctx):
+    if ctx.attr.label and ctx.attr.path:
+        fail("{TOOL_NAME}_toolchain must not specify both label and path.")
+    valid = bool(ctx.attr.label) or bool(ctx.attr.path)
+    toolchain_info = platform_common.ToolchainInfo(
+        {TOOL_NAME} = ToolInfo(
+            name = str(ctx.label),
+            valid = valid,
+            label = ctx.attr.label,
+            path = ctx.attr.path,
+            version = ctx.attr.version,
+        ),
+    )
+    return [toolchain_info]
+
+{TOOL_NAME}_toolchain = rule(
+    implementation = _{TOOL_NAME}_toolchain_impl,
+    attrs = {
+        "label": attr.label(
+            doc = "A valid label of a target to build or a prebuilt binary. Mutually exclusive with path.",
+            cfg = "exec",
+            executable = True,
+            allow_files = True,
+        ),
+        "path": attr.string(
+            doc = "The path to the executable. Mutually exclusive with label.",
+        ),
+        "version": attr.string(
+            doc = "The version string of the executable. This should be manually set.",
+        ),
+    },
+)
+
+# Expose the presence of {TOOL_NAME} in the resolved toolchain as a flag.
+# The signal is to look at the default toolchain of the {TOOL_NAME}_toolchan_type
+# and see that it is valid (that is, it has a path).
+def _is_{TOOL_NAME}_available_impl(ctx):
+    toolchain = ctx.toolchains["@{TOOL_NAME}//:{TOOL_NAME}_toolchain_type"].{TOOL_NAME}
+    return [config_common.FeatureFlagInfo(
+        value = ("1" if toolchain.valid else "0"),
+    )]
+
+is_{TOOL_NAME}_available = rule(
+    implementation = _is_{TOOL_NAME}_available_impl,
+    attrs = {},
+    toolchains = ["@{TOOL_NAME}//:{TOOL_NAME}_toolchain_type"],
+)

bazel/toolchains/pkgbuild/BUILD.bazel

@@ -0,0 +1,8 @@
+"""Toolchain to wrap the pkgbuild binary.
+
+Type: @macos_pkgbuild//:tool_toolchain_type
+
+Toolchains:
+- @macos_pkgbuild//:macos_pkgbuild_toolchain: provides the tool
+- @macos_pkgbuild//:macos_pkgbuild_missing_toolchain: provides a fallback toolchain for exec platforms where pkgbuild might not be available.
+"""

bazel/toolchains/pkgbuild/configure.bzl

@@ -0,0 +1,12 @@
+"""Repository rule to autoconfigure a toolchain using the system pkgbuild."""
+
+load("//bazel/toolchains/common:defs.bzl", "make_repo_builder")
+
+# This must match the name used by register_toolchains in MODULE.bazel.
+NAME = "macos_pkgbuild"
+
+build_repo_for_toolchain = make_repo_builder(name = NAME)
+
+find_macos_pkgbuild = module_extension(
+    implementation = lambda ctx: build_repo_for_toolchain(name = NAME),
+)