From d271e4bde6ec976661454c297f4442f65724e43c Mon Sep 17 00:00:00 2001
From: Eric <eric@dgren.dev>
Date: Wed, 4 Mar 2026 07:52:24 +0000
Subject: [PATCH] feat: add phase 7 bun_install module extension

---
 README.md                                     |  5 ++++
 bun/BUILD.bazel                               |  5 +++-
 bun/extensions.bzl                            | 25 +++++++++++++++++++
 tests/install_extension_test/BUILD.bazel      |  8 ++++++
 .../extension_shape_test.sh                   |  9 +++++++
 5 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 tests/install_extension_test/BUILD.bazel
 create mode 100755 tests/install_extension_test/extension_shape_test.sh

diff --git a/README.md b/README.md
index 43598c1..f65b7fc 100644
--- a/README.md
+++ b/README.md
@@ -40,3 +40,8 @@ Phase 6 bootstrap is in place:
 - Source grouping rules `js_library` / `ts_library` (`/internal/js_library.bzl`)
 - Transitive `deps` propagation wired into `bun_bundle` and `bun_test`
 - Focused dependency-propagation tests (`//tests/library_test:all`)
+
+Phase 7 bootstrap is in place:
+
+- Bzlmod `bun_install` module extension (`/bun/extensions.bzl`) using Bazel 9-compatible extension/tag syntax
+- Focused module-extension shape test (`//tests/install_extension_test:all`)
diff --git a/bun/BUILD.bazel b/bun/BUILD.bazel
index ba771e6..c1895c7 100644
--- a/bun/BUILD.bazel
+++ b/bun/BUILD.bazel
@@ -1,7 +1,10 @@
 load(":toolchain.bzl", "bun_toolchain")
 load(":version.bzl", "BUN_VERSION")
 
-exports_files(["defs.bzl"])
+exports_files([
+    "defs.bzl",
+    "extensions.bzl",
+])
 
 toolchain_type(name = "toolchain_type")
 
diff --git a/bun/extensions.bzl b/bun/extensions.bzl
index bb9ea75..cb25371 100644
--- a/bun/extensions.bzl
+++ b/bun/extensions.bzl
@@ -1,4 +1,5 @@
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("//internal:bun_install.bzl", _bun_install_repository = "_bun_install_repository")
 load(":version.bzl", "BUN_VERSION")
 
 _BUN_ARCHIVES = {
@@ -53,3 +54,27 @@ filegroup(
 bun = module_extension(
     implementation = _bun_repos_impl,
 )
+
+_install = tag_class(
+    attrs = {
+        "name": attr.string(default = "node_modules"),
+        "package_json": attr.string(mandatory = True),
+        "bun_lockfile": attr.string(mandatory = True),
+    },
+)
+
+
+def _bun_install_impl(ctx):
+    for mod in ctx.modules:
+        for install in mod.tags.install:
+            _bun_install_repository(
+                name = install.name,
+                package_json = install.package_json,
+                bun_lockfile = install.bun_lockfile,
+            )
+
+
+bun_install = module_extension(
+    implementation = _bun_install_impl,
+    tag_classes = {"install": _install},
+)
diff --git a/tests/install_extension_test/BUILD.bazel b/tests/install_extension_test/BUILD.bazel
new file mode 100644
index 0000000..bdf75d8
--- /dev/null
+++ b/tests/install_extension_test/BUILD.bazel
@@ -0,0 +1,8 @@
+load("@rules_shell//shell:sh_test.bzl", "sh_test")
+
+sh_test(
+    name = "bun_install_extension_shape_test",
+    srcs = ["extension_shape_test.sh"],
+    args = ["$(location //bun:extensions.bzl)"],
+    data = ["//bun:extensions.bzl"],
+)
diff --git a/tests/install_extension_test/extension_shape_test.sh b/tests/install_extension_test/extension_shape_test.sh
new file mode 100755
index 0000000..a2f9aa1
--- /dev/null
+++ b/tests/install_extension_test/extension_shape_test.sh
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+extension_file="$1"
+
+grep -q 'bun_install = module_extension(' "${extension_file}"
+grep -q 'tag_classes = {"install": _install}' "${extension_file}"
+grep -q '"package_json": attr.string(mandatory = True)' "${extension_file}"
+grep -q '"bun_lockfile": attr.string(mandatory = True)' "${extension_file}"