stable-3.6: fix: call transaction_order() to get deterministic install ordering

client/goal.c

@@ -391,6 +391,7 @@ TDNFSolv(
             BAIL_ON_TDNF_ERROR(dwError);
         }
 
+        transaction_order(pTrans, 0);
         if (pTdnf->pConf->ppszProtectedPkgs) {
             /* catch protected obsoleted packages, and double check for removals */
             dwError = TDNFSolvCheckProtectPkgsInTrans(pTdnf, pTrans, pTdnf->pSack->pPool);

pytests/repo/tdnf-test-prein-base.spec

@@ -0,0 +1,21 @@
+Summary:    Test package - prein ordering base dependency
+Name:       tdnf-test-prein-base
+Version:    1.0
+Release:    1
+Vendor:     VMware, Inc.
+Distribution:   Photon
+License:    VMware
+Url:        http://www.vmware.com
+Group:      Applications/tdnftest
+
+%description
+Base package required by tdnf-test-prein-dep-a to give it more graph
+weight than tdnf-test-prein-dep-b for transaction ordering tests.
+
+%prep
+%build
+%install
+%files
+%changelog
+*   Fri Aug 21 2026 tdnf team 1.0-1
+-   Initial package

pytests/repo/tdnf-test-prein-consumer.spec

@@ -0,0 +1,27 @@
+Summary:    Test package - prein ordering regression, consumer
+Name:       tdnf-test-prein-consumer
+Version:    1.0
+Release:    1
+Vendor:     VMware, Inc.
+Distribution:   Photon
+License:    VMware
+Url:        http://www.vmware.com
+Group:      Applications/tdnftest
+Requires(pre): tdnf-test-prein-cap
+
+%description
+Consumer of tdnf-test-prein-cap via Requires(pre). The %pre scriptlet
+ends with a never-taken if branch to verify POSIX sh exit-code semantics.
+
+%pre
+if [ "%{name}" = "not-this-name" ]; then
+    echo "unreachable"
+fi
+
+%prep
+%build
+%install
+%files
+%changelog
+*   Fri Aug 21 2026 tdnf team 1.0-1
+-   Initial package

pytests/repo/tdnf-test-prein-dep-a.spec

@@ -0,0 +1,24 @@
+Summary:    Test package - prein ordering regression, provider A
+Name:       tdnf-test-prein-dep-a
+Version:    1.0
+Release:    1
+Vendor:     VMware, Inc.
+Distribution:   Photon
+License:    VMware
+Url:        http://www.vmware.com
+Group:      Applications/tdnftest
+Provides:   tdnf-test-prein-cap
+Requires:   tdnf-test-prein-base
+
+%description
+Provider A of tdnf-test-prein-cap. Requires tdnf-test-prein-base to gain
+enough graph weight that transaction_order() consistently places it right
+before the consumer (and after dep-b) in the install sequence.
+
+%prep
+%build
+%install
+%files
+%changelog
+*   Fri Aug 21 2026 tdnf team 1.0-1
+-   Initial package

pytests/repo/tdnf-test-prein-dep-b.spec

@@ -0,0 +1,22 @@
+Summary:    Test package - prein ordering regression, provider B
+Name:       tdnf-test-prein-dep-b
+Version:    1.0
+Release:    1
+Vendor:     VMware, Inc.
+Distribution:   Photon
+License:    VMware
+Url:        http://www.vmware.com
+Group:      Applications/tdnftest
+Provides:   tdnf-test-prein-cap
+
+%description
+Provider B of tdnf-test-prein-cap. No dependencies, giving it less graph
+weight than dep-a so transaction_order() consistently places it earlier.
+
+%prep
+%build
+%install
+%files
+%changelog
+*   Fri Aug 21 2026 tdnf team 1.0-1
+-   Initial package

pytests/tests/test_transaction_order.py

@@ -0,0 +1,60 @@
+#
+# Copyright (C) 2026 VMware, Inc. All Rights Reserved.
+#
+# Licensed under the GNU General Public License v2 (the "License");
+# you may not use this file except in compliance with the License. The terms
+# of the License are located in the COPYING file of this distribution.
+#
+
+import pytest
+
+PREIN_BASE = "tdnf-test-prein-base"
+PREIN_DEP_A = "tdnf-test-prein-dep-a"
+PREIN_DEP_B = "tdnf-test-prein-dep-b"
+PREIN_CONSUMER = "tdnf-test-prein-consumer"
+PREIN_PKGS = [PREIN_BASE, PREIN_DEP_A, PREIN_DEP_B, PREIN_CONSUMER]
+
+
+@pytest.fixture(scope="function", autouse=True)
+def cleanup_prein_packages(utils):
+    utils.run(["tdnf", "remove", "-y"] + PREIN_PKGS)
+    yield
+    utils.run(["tdnf", "remove", "-y"] + PREIN_PKGS)
+
+
+def _install_and_get_order(utils, pkgs):
+    ret = utils.run(["tdnf", "install", "-y", "--nogpgcheck"] + pkgs)
+    assert ret["retval"] == 0, "tdnf install failed (retval={}):\n{}".format(
+        ret["retval"], "\n".join(ret["stdout"] + ret["stderr"])
+    )
+    return [line for line in ret["stdout"] if line.startswith("Installing/Updating:")]
+
+
+def _remove_prein_packages(utils):
+    ret = utils.run(["tdnf", "remove", "-y"] + PREIN_PKGS)
+    assert ret["retval"] == 0, "tdnf remove failed (retval={}):\n{}".format(
+        ret["retval"], "\n".join(ret["stdout"] + ret["stderr"])
+    )
+
+
+# Regression test for transaction_order() fix in client/goal.c:
+# without the fix, solver_create_transaction() leaves pTrans->steps in
+# CLI-argument order; rpmtsOrder() then picks whichever Requires(pre)
+# provider appears closest to the consumer as the ordering anchor, making
+# the install sequence depend on CLI argument order.
+def test_prein_install_order_is_deterministic(utils):
+    order_a_first = _install_and_get_order(
+        utils, [PREIN_DEP_A, PREIN_DEP_B, PREIN_CONSUMER]
+    )
+
+    _remove_prein_packages(utils)
+
+    order_b_first = _install_and_get_order(
+        utils, [PREIN_DEP_B, PREIN_DEP_A, PREIN_CONSUMER]
+    )
+
+    assert order_a_first == order_b_first, (
+        "Install order differed with different CLI argument order -- "
+        "transaction_order() may not be called after solver_create_transaction().\n"
+        "dep-a first: {}\ndep-b first: {}".format(order_a_first, order_b_first)
+    )