From 9b53eca317e52dffa1ba8972981af7b40392e323 Mon Sep 17 00:00:00 2001
From: Alex Sweet <asweet@ss8.com>
Date: Tue, 29 Jun 2021 07:13:20 -0700
Subject: CPack/RPM: Fix weak dep support

RPM 4.11.3 for el7 contains backported support for the RPM weak dep tags.
It only supports querying those tags, but rpmbuild can not make use of them.
Since CPack relies on rpmbuild --querytags to check for support, this
commit switches to rpm --suggests to check for support of weak
dependencies.

Fixes: #22350
---
 Help/cpack_gen/rpm.rst                             |  6 ++++--
 Modules/Internal/CPack/CPackRPM.cmake              | 15 +++++++++++++++
 .../CPack/tests/SUGGESTS/VerifyResult.cmake        | 20 +++++++++-----------
 .../CPack/tests/SUGGESTS/test_suggests.spec        | 22 ++++++++++++++++++++++
 4 files changed, 50 insertions(+), 13 deletions(-)
 create mode 100644 Tests/RunCMake/CPack/tests/SUGGESTS/test_suggests.spec

diff --git a/Help/cpack_gen/rpm.rst b/Help/cpack_gen/rpm.rst
index 5260a1d..322ab68 100644
--- a/Help/cpack_gen/rpm.rst
+++ b/Help/cpack_gen/rpm.rst
@@ -394,8 +394,10 @@ List of CPack RPM generator specific variables:
  * Mandatory : NO
  * Default   : -
 
- May be used to set weak RPM dependencies (suggests). Note that you must
- enclose the complete requires string between quotes.
+ May be used to set weak RPM dependencies (suggests). If ``rpmbuild`` doesn't
+ support the ``Suggests`` tag, CPack will emit a warning and ignore this
+ variable. Note that you must enclose the complete requires string between
+ quotes.
 
 .. variable:: CPACK_RPM_PACKAGE_PROVIDES
               CPACK_RPM_<component>_PACKAGE_PROVIDES
diff --git a/Modules/Internal/CPack/CPackRPM.cmake b/Modules/Internal/CPack/CPackRPM.cmake
index bece2dd..47d2a5c 100644
--- a/Modules/Internal/CPack/CPackRPM.cmake
+++ b/Modules/Internal/CPack/CPackRPM.cmake
@@ -1074,6 +1074,21 @@ function(cpack_rpm_generate_package)
     OUTPUT_STRIP_TRAILING_WHITESPACE)
   string(REPLACE "\n" ";" RPMBUILD_TAG_LIST "${RPMBUILD_TAG_LIST}")
 
+  # In some versions of RPM, weak dependency tags are present in the --querytags
+  # list, but unsupported by rpmbuild. A different method must be used to check
+  # if they are supported.
+
+  execute_process(
+    COMMAND ${RPM_EXECUTABLE} --suggests
+    ERROR_QUIET
+    RESULT_VARIABLE RPMBUILD_SUGGESTS_RESULT)
+
+  if(NOT RPMBUILD_SUGGESTS_RESULT EQUAL 0)
+    foreach(_WEAK_DEP SUGGESTS RECOMMENDS SUPPLEMENTS ENHANCES)
+      list(REMOVE_ITEM RPMBUILD_TAG_LIST ${_WEAK_DEP})
+    endforeach()
+  endif()
+
   if(CPACK_RPM_PACKAGE_EPOCH)
     set(TMP_RPM_EPOCH "Epoch: ${CPACK_RPM_PACKAGE_EPOCH}")
   endif()
diff --git a/Tests/RunCMake/CPack/tests/SUGGESTS/VerifyResult.cmake b/Tests/RunCMake/CPack/tests/SUGGESTS/VerifyResult.cmake
index 61ce752..d1d615b 100644
--- a/Tests/RunCMake/CPack/tests/SUGGESTS/VerifyResult.cmake
+++ b/Tests/RunCMake/CPack/tests/SUGGESTS/VerifyResult.cmake
@@ -1,15 +1,13 @@
-execute_process(COMMAND ${RPMBUILD_EXECUTABLE} --querytags
-                OUTPUT_VARIABLE RPMBUILD_CAPS
-                RESULT_VARIABLE RPMBUILD_CAPS_RESULT)
+# CPack uses `rpm --suggests` to check if rpmbuild supports the "Suggests:" tag.
+# This test intentionally uses a different method (build a test .spec) so any
+# problems will be caught early if functionality should change in the future.
+execute_process(
+  COMMAND ${RPMBUILD_EXECUTABLE} --nobuild test_suggests.spec
+  ERROR_QUIET
+  RESULT_VARIABLE RPMBUILD_SUGGESTS_RESULT)
 
-if(NOT RPMBUILD_CAPS_RESULT)
-  string(REPLACE "\n" ";" RPMBUILD_CAPS "${RPMBUILD_CAPS}")
-  cmake_policy(PUSH)
-    cmake_policy(SET CMP0057 NEW)
-    if(SUGGESTS IN_LIST RPMBUILD_CAPS)
-      set(should_contain_suggests_tag_ true)
-    endif()
-  cmake_policy(POP)
+if(RPMBUILD_SUGGESTS_RESULT EQUAL 0)
+  set(should_contain_suggests_tag_ true)
 endif()
 
 # Only verify that suggests tag is present only if that tag is supported.
diff --git a/Tests/RunCMake/CPack/tests/SUGGESTS/test_suggests.spec b/Tests/RunCMake/CPack/tests/SUGGESTS/test_suggests.spec
new file mode 100644
index 0000000..e766fa9
--- /dev/null
+++ b/Tests/RunCMake/CPack/tests/SUGGESTS/test_suggests.spec
@@ -0,0 +1,22 @@
+# This spec file is used to check if the provided version of rpmbuild supports the "Suggests:" tag
+
+Name:           test
+Version:        0
+Release:        1
+Summary:        test
+License:        test
+
+Suggests: suggested_package
+
+%description
+
+
+%prep
+
+%build
+%configure
+%install
+%clean
+%files
+%doc
+%changelog
-- 
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