fix: don't save lockfile if --frozen-lockfile or --no-save

src/install/install.zig

@@ -7562,6 +7562,7 @@ pub const PackageManager = struct {
                 if (cli.no_save) {
                     this.do.save_lockfile = false;
                     this.do.write_package_json = false;
+                    this.enable.frozen_lockfile = true;
                 }
 
                 if (cli.dry_run) {
@@ -15254,6 +15255,8 @@ pub const PackageManager = struct {
 
         // It's unnecessary work to re-save the lockfile if there are no changes
         const should_save_lockfile =
+            // never save if frozen
+            !manager.options.enable.frozen_lockfile and
             (load_result == .ok and ((load_result.ok.format == .binary and save_format == .text) or
 
             // make sure old versions are updated

test/regression/issue/16646/16646.test.ts

@@ -0,0 +1,58 @@
+import { expect, test } from "bun:test";
+import fs from "fs";
+import { bunEnv, bunExe, tmpdirSync } from "harness";
+import { join } from "path";
+
+test("bun install does create a new lockfile", async () => {
+  const testDir = tmpdirSync();
+  fs.cpSync(join(import.meta.dir), testDir, {
+    recursive: true,
+  });
+  const { exitCode, stderr } = Bun.spawnSync([bunExe(), "install"], {
+    env: bunEnv,
+    cwd: testDir,
+  });
+  const err = stderr.toString();
+  expect(err).toContain("Saved lockfile");
+
+  const bunLock = Bun.file(join(testDir, "bun.lock"));
+  expect(await bunLock.exists()).toBeTrue();
+
+  expect(exitCode).toBe(0);
+});
+
+test("bun install --frozen-lockfile does not create a new lockfile", async () => {
+  const testDir = tmpdirSync();
+  fs.cpSync(join(import.meta.dir), testDir, {
+    recursive: true,
+  });
+  const { exitCode, stderr } = Bun.spawnSync([bunExe(), "install", "--frozen-lockfile"], {
+    env: bunEnv,
+    cwd: testDir,
+  });
+  const err = stderr.toString();
+  expect(err).not.toContain("Saved lockfile");
+
+  const bunLock = Bun.file(join(testDir, "bun.lock"));
+  expect(await bunLock.exists()).toBeFalse();
+
+  expect(exitCode).toBe(0);
+});
+
+test("bun install --no-save does not create a new lockfile", async () => {
+  const testDir = tmpdirSync();
+  fs.cpSync(join(import.meta.dir), testDir, {
+    recursive: true,
+  });
+  const { exitCode, stderr } = Bun.spawnSync([bunExe(), "install", "--no-save"], {
+    env: bunEnv,
+    cwd: testDir,
+  });
+  const err = stderr.toString();
+  expect(err).not.toContain("Saved lockfile");
+
+  const bunLock = Bun.file(join(testDir, "bun.lock"));
+  expect(await bunLock.exists()).toBeFalse();
+
+  expect(exitCode).toBe(0);
+});