1 files changed, 108 insertions, 0 deletions
diff --git a/src/which_npm_client.zig b/src/which_npm_client.zig
new file mode 100644
index 000000000..86683a368
--- /dev/null
+++ b/src/which_npm_client.zig
@@ -0,0 +1,108 @@
+usingnamespace @import("./global.zig");
+
+const which = @import("./which.zig").which;
+const std = @import("std");
+
+pub const NPMClient = struct {
+    bin: string,
+    tag: Tag,
+
+    pub const Tag = enum {
+        npm,
+        yarn,
+        pnpm,
+    };
+
+    pub fn isYarnBerry(allocator: *std.mem.Allocator, yarn_path: string) bool {
+        var args = [_]string{ yarn_path, "--version" };
+        var child_process = std.ChildProcess.init(&args, allocator) catch return true;
+        defer child_process.deinit();
+        child_process.cwd_dir = std.fs.cwd();
+        child_process.expand_arg0 = .no_expand;
+        child_process.stdout_behavior = .Pipe;
+        child_process.stderr_behavior = .Pipe;
+        child_process.spawn() catch return true;
+        defer _ = child_process.kill() catch undefined;
+
+        var path_buf: [512]u8 = undefined;
+        var path_len = child_process.stdout.?.read(&path_buf) catch return true;
+
+        if (path_len == 0) {
+            return true;
+        }
+
+        return path_buf[0] != '1';
+    }
+
+    pub fn detect(allocator: *std.mem.Allocator, realpath_buf: *[std.fs.MAX_PATH_BYTES]u8, PATH: string, cwd: string, comptime allow_yarn: bool) !?NPMClient {
+
+        // We say:
+        // - pnpm if it exists, is the default. its most esoteric, so if you have it installed, you prob want it.
+        // - yarn if it exists and it is yarn 1, its the default (yarn 2 or later is not supported)
+        // - else npm
+        var path_buf: [std.fs.MAX_PATH_BYTES]u8 = undefined;
+
+        const path: [:0]const u8 = brk: {
+            if (comptime allow_yarn) {
+                break :brk which(
+                    &path_buf,
+                    PATH,
+                    cwd,
+                    "pnpm",
+                ) orelse which(
+                    &path_buf,
+                    PATH,
+                    cwd,
+                    "yarn",
+                ) orelse which(
+                    &path_buf,
+                    PATH,
+                    cwd,
+                    "npm",
+                ) orelse "";
+            } else {
+                break :brk which(
+                    &path_buf,
+                    PATH,
+                    cwd,
+                    "pnpm",
+                ) orelse which(
+                    &path_buf,
+                    PATH,
+                    cwd,
+                    "npm",
+                ) orelse "";
+            }
+            unreachable;
+        };
+
+        var basename = std.fs.path.basename(path);
+        if (basename.len == 0) return null;
+
+        if (comptime allow_yarn) {
+            if (std.mem.indexOf(u8, basename, "yarn") != null) {
+                if (isYarnBerry(allocator, path)) {
+                    return try detect(allocator, realpath_buf, PATH, cwd, false);
+                }
+            }
+        }
+
+        var file = std.fs.openFileAbsoluteZ(path, .{ .read = true }) catch return null;
+        defer file.close();
+        const out_path = std.os.getFdPath(file.handle, realpath_buf) catch return null;
+
+        if (strings.contains(basename, "pnpm")) {
+            return NPMClient{ .bin = out_path, .tag = .pnpm };
+        }
+
+        if (strings.contains(basename, "yarn")) {
+            return NPMClient{ .bin = out_path, .tag = .yarn };
+        }
+
+        if (strings.contains(basename, "npm")) {
+            return NPMClient{ .bin = out_path, .tag = .npm };
+        }
+
+        return null;
+    }
+};