From 9e9e2e5a833c9c3e07532f200df2edf86baa2515 Mon Sep 17 00:00:00 2001
From: David Stosik <816901+davidstosik@users.noreply.github.com>
Date: Wed, 1 Jul 2026 22:04:55 +0900
Subject: [PATCH] Respect Gemfile lockfile in `bundle lock`

Use the lockfile path resolved from the definition when no explicit `--lockfile` option is passed.
---
 lib/bundler/cli/lock.rb    |  2 +-
 spec/commands/lock_spec.rb | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/lib/bundler/cli/lock.rb b/lib/bundler/cli/lock.rb
index 2f78868936c1..a1359f63715a 100644
--- a/lib/bundler/cli/lock.rb
+++ b/lib/bundler/cli/lock.rb
@@ -69,7 +69,7 @@ def run
           puts definition.to_lock
         else
           file = options[:lockfile]
-          file = file ? Pathname.new(file).expand_path : Bundler.default_lockfile
+          file = file ? Pathname.new(file).expand_path : definition.lockfile
 
           puts "Writing lockfile to #{file}"
           definition.write_lock(file, false)
diff --git a/spec/commands/lock_spec.rb b/spec/commands/lock_spec.rb
index 4914c11cc3f8..fde728a2675f 100644
--- a/spec/commands/lock_spec.rb
+++ b/spec/commands/lock_spec.rb
@@ -177,6 +177,23 @@
     expect(read_lockfile).to eq(expected_lockfile)
   end
 
+  it "writes the lockfile configured in the Gemfile" do
+    build_repo4 do
+      build_gem "foo", "1.0"
+    end
+
+    gemfile <<-G
+      source "https://gem.repo4"
+      gem "foo", "1.0"
+      lockfile "custom.lock"
+    G
+
+    bundle "lock"
+
+    expect(bundled_app("Gemfile.lock")).not_to exist
+    expect(bundled_app("custom.lock")).to exist
+  end
+
   it "prints a lockfile without fetching new checksums if the existing lockfile had no checksums" do
     gemfile_with_rails_weakling_and_foo_from_repo4