From f03598407bede84a9d24f015f5235e2b273daf0d Mon Sep 17 00:00:00 2001
From: Eric <eric@dgren.dev>
Date: Wed, 4 Mar 2026 03:30:07 +0000
Subject: [PATCH] feat: implement phase 5 bun_bundle bootstrap

---
 README.md                          |  6 +++
 bun/defs.bzl                       |  2 +
 internal/bun_bundle.bzl            | 78 +++++++++++++++++++++++++++++-
 tests/bundle_test/BUILD.bazel      | 48 ++++++++++++++++++
 tests/bundle_test/main.ts          |  5 ++
 tests/bundle_test/verify_bundle.sh | 14 ++++++
 tests/bundle_test/verify_minify.sh | 13 +++++
 7 files changed, 164 insertions(+), 2 deletions(-)
 create mode 100644 tests/bundle_test/BUILD.bazel
 create mode 100644 tests/bundle_test/main.ts
 create mode 100755 tests/bundle_test/verify_bundle.sh
 create mode 100755 tests/bundle_test/verify_minify.sh

diff --git a/README.md b/README.md
index e81d03f..4b178e5 100644
--- a/README.md
+++ b/README.md
@@ -28,3 +28,9 @@ Phase 4 bootstrap is in place:
 - Test rule `bun_test` (`/internal/bun_test.bzl`)
 - Public export via `bun/defs.bzl`
 - Focused passing/failing test targets (`//tests/bun_test_test:all`)
+
+Phase 5 bootstrap is in place:
+
+- Bundle rule `bun_bundle` (`/internal/bun_bundle.bzl`)
+- Public export via `bun/defs.bzl`
+- Focused output/minify tests (`//tests/bundle_test:all`)
diff --git a/bun/defs.bzl b/bun/defs.bzl
index 0664176..b19a324 100644
--- a/bun/defs.bzl
+++ b/bun/defs.bzl
@@ -1,4 +1,5 @@
 load("//internal:bun_binary.bzl", "bun_binary")
+load("//internal:bun_bundle.bzl", "bun_bundle")
 load("//internal:bun_install.bzl", "bun_install")
 load("//internal:bun_test.bzl", "bun_test")
 load(":repositories.bzl", "bun_register_toolchains", "bun_repositories")
@@ -7,6 +8,7 @@ load(":toolchain.bzl", "BunToolchainInfo", "bun_toolchain")
 __all__ = [
     "BunToolchainInfo",
     "bun_binary",
+    "bun_bundle",
     "bun_install",
     "bun_test",
     "bun_register_toolchains",
diff --git a/internal/bun_bundle.bzl b/internal/bun_bundle.bzl
index b430850..13af4bc 100644
--- a/internal/bun_bundle.bzl
+++ b/internal/bun_bundle.bzl
@@ -1,2 +1,76 @@
-def bun_bundle(**_kwargs):
-    fail("bun_bundle is not implemented yet")
+"""Rule for bundling JS/TS sources with Bun."""
+
+
+def _output_name(target_name, entry):
+    stem = entry.basename.rsplit(".", 1)[0]
+    return "{}__{}.js".format(target_name, stem)
+
+
+def _bun_bundle_impl(ctx):
+    toolchain = ctx.toolchains["//bun:toolchain_type"]
+    bun_bin = toolchain.bun.bun_bin
+
+    transitive_inputs = []
+    if ctx.attr.node_modules:
+        transitive_inputs.append(ctx.attr.node_modules[DefaultInfo].files)
+
+    outputs = []
+    for entry in ctx.files.entry_points:
+        output = ctx.actions.declare_file(_output_name(ctx.label.name, entry))
+        outputs.append(output)
+
+        args = ctx.actions.args()
+        args.add("build")
+        args.add(entry.path)
+        args.add("--outfile")
+        args.add(output.path)
+        args.add("--target")
+        args.add(ctx.attr.target)
+        args.add("--format")
+        args.add(ctx.attr.format)
+        if ctx.attr.minify:
+            args.add("--minify")
+        if ctx.attr.sourcemap:
+            args.add("--sourcemap")
+        for package in ctx.attr.external:
+            args.add("--external")
+            args.add(package)
+
+        ctx.actions.run(
+            executable = bun_bin,
+            arguments = [args],
+            inputs = depset(
+                direct = [entry] + ctx.files.data,
+                transitive = transitive_inputs,
+            ),
+            outputs = [output],
+            mnemonic = "BunBundle",
+            progress_message = "Bundling {} with Bun".format(entry.short_path),
+        )
+
+    return [DefaultInfo(files = depset(outputs))]
+
+
+bun_bundle = rule(
+    implementation = _bun_bundle_impl,
+    attrs = {
+        "entry_points": attr.label_list(
+            mandatory = True,
+            allow_files = [".js", ".ts", ".jsx", ".tsx", ".mjs", ".cjs"],
+        ),
+        "node_modules": attr.label(),
+        "data": attr.label_list(allow_files = True),
+        "target": attr.string(
+            default = "browser",
+            values = ["browser", "node", "bun"],
+        ),
+        "format": attr.string(
+            default = "esm",
+            values = ["esm", "cjs", "iife"],
+        ),
+        "minify": attr.bool(default = False),
+        "sourcemap": attr.bool(default = False),
+        "external": attr.string_list(),
+    },
+    toolchains = ["//bun:toolchain_type"],
+)
diff --git a/tests/bundle_test/BUILD.bazel b/tests/bundle_test/BUILD.bazel
new file mode 100644
index 0000000..2417e43
--- /dev/null
+++ b/tests/bundle_test/BUILD.bazel
@@ -0,0 +1,48 @@
+load("//bun:defs.bzl", "bun_bundle")
+
+bun_bundle(
+    name = "simple_bundle",
+    entry_points = ["main.ts"],
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+)
+
+bun_bundle(
+    name = "minified_bundle",
+    entry_points = ["main.ts"],
+    minify = True,
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+)
+
+sh_test(
+    name = "bundle_output_test",
+    srcs = ["verify_bundle.sh"],
+    args = ["$(location :simple_bundle)"],
+    data = [":simple_bundle"],
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+)
+
+sh_test(
+    name = "bundle_minify_test",
+    srcs = ["verify_minify.sh"],
+    args = [
+        "$(location :simple_bundle)",
+        "$(location :minified_bundle)",
+    ],
+    data = [
+        ":simple_bundle",
+        ":minified_bundle",
+    ],
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+)
diff --git a/tests/bundle_test/main.ts b/tests/bundle_test/main.ts
new file mode 100644
index 0000000..ff55828
--- /dev/null
+++ b/tests/bundle_test/main.ts
@@ -0,0 +1,5 @@
+export function greet(name: string): string {
+  return `Hello ${name}`;
+}
+
+console.log(greet("bundle"));
diff --git a/tests/bundle_test/verify_bundle.sh b/tests/bundle_test/verify_bundle.sh
new file mode 100755
index 0000000..b0122f9
--- /dev/null
+++ b/tests/bundle_test/verify_bundle.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+bundle="$1"
+
+if [[ ! -f "${bundle}" ]]; then
+  echo "Bundle output not found: ${bundle}" >&2
+  exit 1
+fi
+
+if [[ ! -s "${bundle}" ]]; then
+  echo "Bundle output is empty: ${bundle}" >&2
+  exit 1
+fi
diff --git a/tests/bundle_test/verify_minify.sh b/tests/bundle_test/verify_minify.sh
new file mode 100755
index 0000000..eab37d7
--- /dev/null
+++ b/tests/bundle_test/verify_minify.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+bundle="$1"
+minified="$2"
+
+bundle_size="$(wc -c < "${bundle}")"
+minified_size="$(wc -c < "${minified}")"
+
+if (( minified_size >= bundle_size )); then
+  echo "Expected minified bundle (${minified_size}) to be smaller than regular bundle (${bundle_size})" >&2
+  exit 1
+fi