feat: add phase 2 bun_install repository rule bootstrap

Co-authored-by: Eriyc <50216491+Eriyc@users.noreply.github.com>

internal/BUILD.bazel

@@ -0,0 +1 @@
+package(default_visibility = ["//visibility:public"])

internal/bun_install.bzl

@@ -1,2 +1,93 @@
-def bun_install(**_kwargs):
-    fail("bun_install is not implemented yet")
+"""Repository-rule based bun_install implementation."""
+
+def _select_bun_binary(repository_ctx):
+    os_name = repository_ctx.os.name.lower()
+    arch = repository_ctx.os.arch.lower()
+
+    if "linux" in os_name:
+        if arch in ["aarch64", "arm64"]:
+            return repository_ctx.path(repository_ctx.attr.bun_linux_aarch64)
+        return repository_ctx.path(repository_ctx.attr.bun_linux_x64)
+
+    if "mac" in os_name or "darwin" in os_name:
+        if arch in ["aarch64", "arm64"]:
+            return repository_ctx.path(repository_ctx.attr.bun_darwin_aarch64)
+        return repository_ctx.path(repository_ctx.attr.bun_darwin_x64)
+
+    if "windows" in os_name:
+        return repository_ctx.path(repository_ctx.attr.bun_windows_x64)
+
+    fail("Unsupported host platform: os={}, arch={}".format(repository_ctx.os.name, repository_ctx.os.arch))
+
+
+def _bun_install_repository_impl(repository_ctx):
+    package_json = repository_ctx.path(repository_ctx.attr.package_json)
+    bun_lockfile = repository_ctx.path(repository_ctx.attr.bun_lockfile)
+
+    if not package_json.exists:
+        fail("bun_install: package_json not found: {}".format(repository_ctx.attr.package_json))
+
+    if not bun_lockfile.exists:
+        fail("bun_install: bun_lockfile not found: {}".format(repository_ctx.attr.bun_lockfile))
+
+    bun_bin = _select_bun_binary(repository_ctx)
+
+    repository_ctx.symlink(package_json, "package.json")
+    repository_ctx.symlink(bun_lockfile, "bun.lockb")
+
+    result = repository_ctx.execute(
+        [str(bun_bin), "install", "--frozen-lockfile", "--no-progress"],
+        timeout = 600,
+        quiet = False,
+        environment = {"HOME": str(repository_ctx.path("."))},
+    )
+
+    if result.return_code:
+        fail("""bun_install failed running `bun install --frozen-lockfile`.
+stdout:
+{}
+stderr:
+{}
+""".format(result.stdout, result.stderr))
+
+    repository_ctx.file(
+        "BUILD.bazel",
+        """filegroup(
+    name = "node_modules",
+    srcs = glob(["node_modules/**"], allow_empty = False),
+    visibility = ["//visibility:public"],
+)
+""",
+    )
+
+
+_bun_install_repository = repository_rule(
+    implementation = _bun_install_repository_impl,
+    attrs = {
+        "package_json": attr.label(mandatory = True, allow_single_file = True),
+        "bun_lockfile": attr.label(mandatory = True, allow_single_file = True),
+        "bun_linux_x64": attr.label(default = "@bun_linux_x64//:bun", allow_single_file = True),
+        "bun_linux_aarch64": attr.label(default = "@bun_linux_aarch64//:bun", allow_single_file = True),
+        "bun_darwin_x64": attr.label(default = "@bun_darwin_x64//:bun", allow_single_file = True),
+        "bun_darwin_aarch64": attr.label(default = "@bun_darwin_aarch64//:bun", allow_single_file = True),
+        "bun_windows_x64": attr.label(default = "@bun_windows_x64//:bun", allow_single_file = True),
+    },
+)
+
+
+def bun_install(name, package_json, bun_lockfile):
+    """Create an external repository containing installed node_modules.
+
+    Usage (WORKSPACE):
+      bun_install(
+          name = "node_modules",
+          package_json = "//:package.json",
+          bun_lockfile = "//:bun.lockb",
+      )
+    """
+
+    _bun_install_repository(
+        name = name,
+        package_json = package_json,
+        bun_lockfile = bun_lockfile,
+    )