2 files changed, 131 insertions, 0 deletions

diff --git a/src/bun.js/api/bun.zig b/src/bun.js/api/bun.zig
index 8a75c3653..f36549485 100644
--- a/src/bun.js/api/bun.zig
+++ b/src/bun.js/api/bun.zig
@@ -76,6 +76,7 @@ const Transpiler = @import("./transpiler.zig");
 const VirtualMachine = @import("../javascript.zig").VirtualMachine;
 const IOTask = JSC.IOTask;
 const zlib = @import("../../zlib.zig");
+const Which = @import("../../which.zig");
 
 const is_bindgen = JSC.is_bindgen;
 const max_addressible_memory = std.math.maxInt(u56);
@@ -129,6 +130,80 @@ pub fn getCSSImports() []ZigString {
     return css_imports_list_strings[0..tail];
 }
 
+pub fn which(
+    // this
+    _: void,
+    globalThis: js.JSContextRef,
+    // function
+    _: js.JSObjectRef,
+    // thisObject
+    _: js.JSObjectRef,
+    arguments_: []const js.JSValueRef,
+    exception: js.ExceptionRef,
+) js.JSValueRef {
+    var path_buf: [bun.MAX_PATH_BYTES]u8 = undefined;
+    var arguments = JSC.Node.ArgumentsSlice.from(globalThis.bunVM(), arguments_);
+    defer arguments.deinit();
+    const path_arg = arguments.nextEat() orelse {
+        JSC.throwInvalidArguments("which: expected 1 argument, got 0", .{}, globalThis, exception);
+        return JSC.JSValue.jsUndefined().asObjectRef();
+    };
+
+    var path_str: ZigString.Slice = ZigString.Slice.empty;
+    var bin_str: ZigString.Slice = ZigString.Slice.empty;
+    var cwd_str: ZigString.Slice = ZigString.Slice.empty;
+    defer {
+        path_str.deinit();
+        bin_str.deinit();
+        cwd_str.deinit();
+    }
+
+    if (path_arg.isEmptyOrUndefinedOrNull()) {
+        return JSC.JSValue.jsNull().asObjectRef();
+    }
+
+    bin_str = path_arg.toSlice(globalThis, globalThis.bunVM().allocator);
+
+    if (bin_str.len >= bun.MAX_PATH_BYTES) {
+        JSC.throwInvalidArguments("bin path is too long", .{}, globalThis, exception);
+        return JSC.JSValue.jsUndefined().asObjectRef();
+    }
+
+    if (bin_str.len == 0) {
+        return JSC.JSValue.jsNull().asObjectRef();
+    }
+
+    path_str = ZigString.Slice.fromUTF8(
+        globalThis.bunVM().bundler.env.map.get("PATH") orelse "",
+    );
+    cwd_str = ZigString.Slice.fromUTF8(
+        globalThis.bunVM().bundler.fs.top_level_dir,
+    );
+
+    if (arguments.nextEat()) |arg| {
+        if (!arg.isEmptyOrUndefinedOrNull() and arg.isObject()) {
+            if (arg.get(globalThis, "PATH")) |str_| {
+                path_str = str_.toSlice(globalThis, globalThis.bunVM().allocator);
+            }
+
+            if (arg.get(globalThis, "cwd")) |str_| {
+                cwd_str = str_.toSlice(globalThis, globalThis.bunVM().allocator);
+            }
+        }
+    }
+
+    if (Which.which(
+        &path_buf,
+        path_str.slice(),
+        cwd_str.slice(),
+        bin_str.slice(),
+    )) |bin_path| {
+        return ZigString.init(bin_path).withEncoding().toValueGC(globalThis).asObjectRef();
+    }
+
+    return JSC.JSValue.jsNull().asObjectRef();
+}
+
 pub fn inspect(
     // this
     _: void,
@@ -1116,6 +1191,10 @@ pub const Class = NewClass(
         .inflateSync = .{
             .rfn = JSC.wrapWithHasContainer(JSZlib, "inflateSync", false, false, true),
         },
+
+        .which = .{
+            .rfn = which,
+        },
     },
     .{
         .main = .{
diff --git a/test/bun.js/which.test.ts b/test/bun.js/which.test.ts
new file mode 100644
index 000000000..7fd4b8400
--- /dev/null
+++ b/test/bun.js/which.test.ts
@@ -0,0 +1,52 @@
+import { test, expect } from "bun:test";
+
+import { which } from "bun";
+
+test("which", () => {
+  writeFixture("/tmp/myscript.sh");
+
+  // Our cwd is not /tmp
+  expect(which("myscript.sh")).toBe(null);
+
+  // "bun" is in our PATH
+  expect(which("bun")?.length > 0).toBe(true);
+
+  expect(
+    // You can override PATH
+    which("myscript.sh", {
+      PATH: "/tmp",
+    })
+  ).toBe("/tmp/myscript.sh");
+
+  expect(
+    which("myscript.sh", {
+      PATH: "/not-tmp",
+    })
+  ).toBe(null);
+
+  expect(
+    // PATH works like the $PATH environment variable, respecting colons
+    which("myscript.sh", {
+      PATH: "/not-tmp:/tmp",
+    })
+  ).toBe("/tmp/myscript.sh");
+
+  expect(
+    // cwd is checked first
+    which("myscript.sh", {
+      cwd: "/tmp",
+    })
+  ).toBe("/tmp/myscript.sh");
+});
+
+function writeFixture(path) {
+  var fs = require("fs");
+  try {
+    fs.unlinkSync(path);
+  } catch (e) {}
+
+  var script_name = path;
+  var script_content = "echo Hello world!";
+  fs.writeFileSync(script_name, script_content);
+  fs.chmodSync(script_name, "755");
+}