switch esbuild to a toolchain

ts/esbuild.bzl

@@ -3,11 +3,6 @@ load("//ts/esbuild:upstream.bzl", _esbuild = "esbuild_macro")
 def esbuild(name, **kwargs):
     _esbuild(
         name = name,
-        tool = select({
-            "@bazel_tools//src/conditions:darwin": "@esbuild_darwin//:bin/esbuild",
-            "@bazel_tools//src/conditions:windows": "@esbuild_windows//:esbuild.exe",
-            "@bazel_tools//src/conditions:linux_x86_64": "@esbuild_linux//:bin/esbuild",
-        }),
         minify = select({
             "//:release": True,
             "//conditions:default": False,

ts/esbuild/BUILD.bazel

@@ -0,0 +1,8 @@
+load(":toolchain.bzl", "define_default_toolchains", "esbuild_toolchain")
+
+toolchain_type(
+    name = "toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+define_default_toolchains()

ts/esbuild/esbuild_repo.bzl

@@ -5,6 +5,7 @@ Helper macro for fetching esbuild versions for internal tests and examples in ru
 """
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load(":toolchain.bzl", "register_default_toolchains")
 
 _VERSION = "0.11.5"
 
@@ -40,3 +41,5 @@ def esbuild_dependencies():
         build_file_content = """exports_files(["bin/esbuild"])""",
         sha256 = "113c2e84895f4422a3676db4e15d9f01b2b4fac041edab25284fdb9574ba58a0",
     )
+
+    register_default_toolchains()

ts/esbuild/toolchain.bzl

@@ -0,0 +1,42 @@
+def _esbuild_toolchain_impl(ctx):
+    return [platform_common.ToolchainInfo(
+        binary = ctx.executable.binary,
+    )]
+
+esbuild_toolchain = rule(
+    implementation = _esbuild_toolchain_impl,
+    attrs = {
+        "binary": attr.label(allow_single_file = True, executable = True, cfg = "exec"),
+    },
+)
+
+_package_path = "@net_ankiweb_anki//ts/esbuild"
+
+TOOLCHAIN = _package_path + ":toolchain_type"
+
+_default_toolchains = [
+    ["@esbuild_darwin//:bin/esbuild", "macos"],
+    ["@esbuild_linux//:bin/esbuild", "linux"],
+    ["@esbuild_windows//:esbuild.exe", "windows"],
+]
+
+def define_default_toolchains():
+    for repo_path, platform in _default_toolchains:
+        esbuild_toolchain(
+            name = "esbuild_" + platform,
+            binary = repo_path,
+        )
+
+        native.toolchain(
+            name = "esbuild_{}_toolchain".format(platform),
+            exec_compatible_with = [
+                "@platforms//os:" + platform,
+                "@platforms//cpu:x86_64",
+            ],
+            toolchain = ":esbuild_" + platform,
+            toolchain_type = ":toolchain_type",
+        )
+
+def register_default_toolchains():
+    for _, platform in _default_toolchains:
+        native.register_toolchains(_package_path + ":esbuild_{}_toolchain".format(platform))

ts/esbuild/upstream.bzl

@@ -5,6 +5,7 @@ esbuild rule
 load("@build_bazel_rules_nodejs//:providers.bzl", "JSEcmaScriptModuleInfo", "JSModuleInfo", "NpmPackageInfo", "node_modules_aspect")
 load("@build_bazel_rules_nodejs//internal/linker:link_node_modules.bzl", "MODULE_MAPPINGS_ASPECT_RESULTS_NAME", "module_mappings_aspect")
 load(":helpers.bzl", "filter_files", "generate_path_mapping", "resolve_js_input", "write_jsconfig_file")
+load(":toolchain.bzl", "TOOLCHAIN")
 
 def _esbuild_impl(ctx):
     # For each dep, JSEcmaScriptModuleInfo is used if found, then JSModuleInfo and finally
@@ -128,7 +129,7 @@ def _esbuild_impl(ctx):
     ctx.actions.run(
         inputs = inputs,
         outputs = outputs,
-        executable = ctx.executable.tool,
+        executable = ctx.toolchains[TOOLCHAIN].binary,
         arguments = [args],
         progress_message = "%s Javascript %s [esbuild]" % ("Bundling" if not ctx.attr.output_dir else "Splitting", entry_point.short_path),
         execution_requirements = execution_requirements,
@@ -268,19 +269,15 @@ edge16, node10, default esnext)
 See https://esbuild.github.io/api/#target for more details
             """,
         ),
-        "tool": attr.label(
-            allow_single_file = True,
-            mandatory = True,
-            executable = True,
-            cfg = "exec",
-            doc = "An executable for the esbuild binary",
-        ),
     },
     implementation = _esbuild_impl,
     doc = """Runs the esbuild bundler under Bazel
 
 For further information about esbuild, see https://esbuild.github.io/
     """,
+    toolchains = [
+        TOOLCHAIN,
+    ],
 )
 
 def esbuild_macro(name, output_dir = False, output_css = False, **kwargs):