From beb8a72d0d94bf1f2afe8bb7886c4b5544442b53 Mon Sep 17 00:00:00 2001
From: eric <eric@dgren.dev>
Date: Wed, 4 Mar 2026 14:21:45 +0100
Subject: [PATCH] feat: add option for process cwd (.env support)

---
 MODULE.bazel.lock                   |  4 ++--
 README.md                           | 14 ++++++++++++++
 bun/defs.bzl                        |  1 +
 internal/bun_binary.bzl             | 14 +++++++++++++-
 internal/bun_bundle.bzl             |  1 +
 internal/bun_dev.bzl                | 29 ++++++++++++++++++++---------
 internal/bun_install.bzl            |  4 ++--
 internal/bun_test.bzl               |  8 ++++----
 tests/binary_test/BUILD.bazel       | 14 ++++++++++++++
 tests/binary_test/env.ts            |  2 ++
 tests/binary_test/run_env_binary.sh | 10 ++++++++++
 11 files changed, 83 insertions(+), 18 deletions(-)
 create mode 100644 tests/binary_test/env.ts
 create mode 100755 tests/binary_test/run_env_binary.sh

diff --git a/MODULE.bazel.lock b/MODULE.bazel.lock
index 51c7a9a..45dfc91 100644
--- a/MODULE.bazel.lock
+++ b/MODULE.bazel.lock
@@ -189,8 +189,8 @@
   "moduleExtensions": {
     "//bun:extensions.bzl%bun": {
       "general": {
-        "bzlTransitiveDigest": "Q0uQOwFAgAU+etePCZ4TUDO+adLX7Z0EmRLaEsKgncw=",
-        "usagesDigest": "UC4zk8kEwWRiDG5FVQOCFysXcrZ757Jehf3sZgG893w=",
+        "bzlTransitiveDigest": "oLR98WtKDCc+zh7Tvu9jtakNg8q/T1IPE38QR1FEQtI=",
+        "usagesDigest": "9s+/cJR+wTifjBrio71E10Knd41B08/GmW4I9zJmU64=",
         "recordedInputs": [
           "REPO_MAPPING:,bazel_tools bazel_tools"
         ],
diff --git a/README.md b/README.md
index e5ad3c2..d90ae50 100644
--- a/README.md
+++ b/README.md
@@ -103,6 +103,8 @@ Run one of your bun-backed targets, for example:
 bazel test //path/to:your_bun_test
 ```
 
+All `rules_bun` rule-driven Bun invocations pass `--bun`.
+
 ## Development mode (`bun_dev`)
 
 Use `bun_dev` for long-running local development with Bun watch mode.
@@ -113,6 +115,8 @@ load("@rules_bun//bun:defs.bzl", "bun_dev")
 bun_dev(
 	name = "web_dev",
 	entry_point = "src/main.ts",
+	# Optional: run from the entry point directory so Bun auto-loads colocated .env files.
+	# working_dir = "entry_point",
 )
 ```
 
@@ -127,6 +131,16 @@ bazel run //path/to:web_dev
 - `watch_mode = "watch"` (default) for `bun --watch`
 - `watch_mode = "hot"` for `bun --hot`
 - `restart_on = [...]` to force full process restarts when specific files change
+- `working_dir = "workspace" | "entry_point"` (default: `workspace`)
+
+## Runtime working directory (`bun_binary`, `bun_dev`)
+
+`bun_binary` and `bun_dev` support `working_dir`:
+
+- `"workspace"` (default): runs from the Bazel runfiles workspace root.
+- `"entry_point"`: runs from the entry point file's directory.
+
+Use `"entry_point"` when Bun should resolve local files such as colocated `.env` files relative to the program directory.
 
 ### Hybrid Go + Bun + protobuf workflow
 
diff --git a/bun/defs.bzl b/bun/defs.bzl
index 739e89a..baf4960 100644
--- a/bun/defs.bzl
+++ b/bun/defs.bzl
@@ -16,3 +16,4 @@ js_library = _js_library
 ts_library = _ts_library
 BunToolchainInfo = _BunToolchainInfo
 bun_toolchain = _bun_toolchain
+ 
\ No newline at end of file
diff --git a/internal/bun_binary.bzl b/internal/bun_binary.bzl
index f5e76bb..59b6162 100644
--- a/internal/bun_binary.bzl
+++ b/internal/bun_binary.bzl
@@ -17,10 +17,18 @@ runfiles_dir="${{RUNFILES_DIR:-$0.runfiles}}"
 bun_bin="${{runfiles_dir}}/_main/{bun_short_path}"
 entry_point="${{runfiles_dir}}/_main/{entry_short_path}"
 
-exec "${{bun_bin}}" run "${{entry_point}}" "$@"
+working_dir="{working_dir}"
+if [[ "${{working_dir}}" == "entry_point" ]]; then
+    cd "$(dirname "${{entry_point}}")"
+else
+    cd "${{runfiles_dir}}/_main"
+fi
+
+exec "${{bun_bin}}" --bun run "${{entry_point}}" "$@"
 """.format(
             bun_short_path = bun_bin.short_path,
             entry_short_path = entry_point.short_path,
+            working_dir = ctx.attr.working_dir,
         ),
     )
 
@@ -50,6 +58,10 @@ bun_binary = rule(
         ),
         "node_modules": attr.label(),
         "data": attr.label_list(allow_files = True),
+        "working_dir": attr.string(
+            default = "workspace",
+            values = ["workspace", "entry_point"],
+        ),
     },
     executable = True,
     toolchains = ["//bun:toolchain_type"],
diff --git a/internal/bun_bundle.bzl b/internal/bun_bundle.bzl
index 56b6aee..0b45a3f 100644
--- a/internal/bun_bundle.bzl
+++ b/internal/bun_bundle.bzl
@@ -27,6 +27,7 @@ def _bun_bundle_impl(ctx):
         outputs.append(output)
 
         args = ctx.actions.args()
+        args.add("--bun")
         args.add("build")
         args.add(entry.path)
         args.add("--outfile")
diff --git a/internal/bun_dev.bzl b/internal/bun_dev.bzl
index deb9245..5a45c09 100644
--- a/internal/bun_dev.bzl
+++ b/internal/bun_dev.bzl
@@ -1,6 +1,5 @@
 """Rule for running JS/TS scripts with Bun in watch mode for development."""
 
-
 def _bun_dev_impl(ctx):
     toolchain = ctx.toolchains["//bun:toolchain_type"]
     bun_bin = toolchain.bun.bun_bin
@@ -18,7 +17,13 @@ set -euo pipefail
 runfiles_dir="${{RUNFILES_DIR:-$0.runfiles}}"
 bun_bin="${{runfiles_dir}}/_main/{bun_short_path}"
 entry_point="${{runfiles_dir}}/_main/{entry_short_path}"
-cd "${{runfiles_dir}}/_main"
+
+working_dir="{working_dir}"
+if [[ "${{working_dir}}" == "entry_point" ]]; then
+    cd "$(dirname "${{entry_point}}")"
+else
+    cd "${{runfiles_dir}}/_main"
+fi
 
 watch_mode="{watch_mode}"
 if [[ "${{watch_mode}}" == "hot" ]]; then
@@ -28,7 +33,7 @@ else
 fi
 
 run_dev() {{
-    exec "${{bun_bin}}" "${{dev_flag}}" run "${{entry_point}}" "$@"
+    exec "${{bun_bin}}" --bun "${{dev_flag}}" run "${{entry_point}}" "$@"
 }}
 
 if [[ {restart_count} -eq 0 ]]; then
@@ -50,8 +55,9 @@ file_mtime() {{
 
 declare -A mtimes
 for rel in "${{restart_paths[@]}}"; do
-    if [[ -e "${{rel}}" ]]; then
-        mtimes["${{rel}}"]="$(file_mtime "${{rel}}")"
+    path="${{runfiles_dir}}/_main/${{rel}}"
+    if [[ -e "${{path}}" ]]; then
+        mtimes["${{rel}}"]="$(file_mtime "${{path}}")"
     else
         mtimes["${{rel}}"]="missing"
     fi
@@ -63,7 +69,7 @@ restart_child() {{
         kill "${{child_pid}}"
         wait "${{child_pid}}" || true
     fi
-    "${{bun_bin}}" "${{dev_flag}}" run "${{entry_point}}" "$@" &
+    "${{bun_bin}}" --bun "${{dev_flag}}" run "${{entry_point}}" "$@" &
     child_pid=$!
 }}
 
@@ -82,8 +88,9 @@ while true; do
     sleep 1
     changed=0
     for rel in "${{restart_paths[@]}}"; do
-        if [[ -e "${{rel}}" ]]; then
-            current="$(file_mtime "${{rel}}")"
+        path="${{runfiles_dir}}/_main/${{rel}}"
+        if [[ -e "${{path}}" ]]; then
+            current="$(file_mtime "${{path}}")"
         else
             current="missing"
         fi
@@ -100,6 +107,7 @@ done
             bun_short_path = bun_bin.short_path,
             entry_short_path = entry_point.short_path,
             watch_mode = ctx.attr.watch_mode,
+            working_dir = ctx.attr.working_dir,
             restart_count = len(ctx.files.restart_on),
             restart_watch_paths = restart_watch_paths,
         ),
@@ -121,7 +129,6 @@ done
         ),
     ]
 
-
 bun_dev = rule(
     implementation = _bun_dev_impl,
     attrs = {
@@ -136,6 +143,10 @@ bun_dev = rule(
         "restart_on": attr.label_list(allow_files = True),
         "node_modules": attr.label(),
         "data": attr.label_list(allow_files = True),
+        "working_dir": attr.string(
+            default = "workspace",
+            values = ["workspace", "entry_point"],
+        ),
     },
     executable = True,
     toolchains = ["//bun:toolchain_type"],
diff --git a/internal/bun_install.bzl b/internal/bun_install.bzl
index db0a01e..f9a5617 100644
--- a/internal/bun_install.bzl
+++ b/internal/bun_install.bzl
@@ -36,14 +36,14 @@ def _bun_install_repository_impl(repository_ctx):
     repository_ctx.symlink(bun_lockfile, "bun.lockb")
 
     result = repository_ctx.execute(
-        [str(bun_bin), "install", "--frozen-lockfile", "--no-progress"],
+        [str(bun_bin), "--bun", "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`.
+        fail("""bun_install failed running `bun --bun install --frozen-lockfile`.
 stdout:
 {}
 stderr:
diff --git a/internal/bun_test.bzl b/internal/bun_test.bzl
index 29d311e..a08f1d3 100644
--- a/internal/bun_test.bzl
+++ b/internal/bun_test.bzl
@@ -24,15 +24,15 @@ bun_bin="${{runfiles_dir}}/_main/{bun_short_path}"
 cd "${{runfiles_dir}}/_main"
 
 if [[ -n "${{TESTBRIDGE_TEST_ONLY:-}}" && -n "${{COVERAGE_DIR:-}}" ]]; then
-    exec "${{bun_bin}}" test {src_args} --test-name-pattern "${{TESTBRIDGE_TEST_ONLY}}" --coverage "$@"
+    exec "${{bun_bin}}" --bun test {src_args} --test-name-pattern "${{TESTBRIDGE_TEST_ONLY}}" --coverage "$@"
 fi
 if [[ -n "${{TESTBRIDGE_TEST_ONLY:-}}" ]]; then
-    exec "${{bun_bin}}" test {src_args} --test-name-pattern "${{TESTBRIDGE_TEST_ONLY}}" "$@"
+    exec "${{bun_bin}}" --bun test {src_args} --test-name-pattern "${{TESTBRIDGE_TEST_ONLY}}" "$@"
 fi
 if [[ -n "${{COVERAGE_DIR:-}}" ]]; then
-    exec "${{bun_bin}}" test {src_args} --coverage "$@"
+    exec "${{bun_bin}}" --bun test {src_args} --coverage "$@"
 fi
-exec "${{bun_bin}}" test {src_args} "$@"
+exec "${{bun_bin}}" --bun test {src_args} "$@"
 """.format(
                         bun_short_path = bun_bin.short_path,
             src_args = src_args,
diff --git a/tests/binary_test/BUILD.bazel b/tests/binary_test/BUILD.bazel
index 980e2de..369b9c9 100644
--- a/tests/binary_test/BUILD.bazel
+++ b/tests/binary_test/BUILD.bazel
@@ -43,3 +43,17 @@ sh_test(
         "//tests/binary_test:BUILD.bazel",
     ],
 )
+
+bun_binary(
+    name = "env_cwd_bin",
+    entry_point = "env.ts",
+    data = [".env"],
+    working_dir = "entry_point",
+)
+
+sh_test(
+    name = "bun_binary_env_cwd_test",
+    srcs = ["run_env_binary.sh"],
+    args = ["$(location :env_cwd_bin)"],
+    data = [":env_cwd_bin"],
+)
diff --git a/tests/binary_test/env.ts b/tests/binary_test/env.ts
new file mode 100644
index 0000000..9ddbf89
--- /dev/null
+++ b/tests/binary_test/env.ts
@@ -0,0 +1,2 @@
+const value = process.env.BUN_ENV_CWD_TEST ?? "missing";
+console.log(value);
diff --git a/tests/binary_test/run_env_binary.sh b/tests/binary_test/run_env_binary.sh
new file mode 100755
index 0000000..09c8d25
--- /dev/null
+++ b/tests/binary_test/run_env_binary.sh
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+binary="$1"
+output="$(${binary})"
+
+if [[ ${output} != "from-dotenv" ]]; then
+  echo "Expected .env value from entry-point directory, got: ${output}" >&2
+  exit 1
+fi