CPack-deb: don't add a line with a dot to pkg desc

Currently, if the package description ends with a newline
(typically if it is read from a file) cpack -deb adds a single line
with a dot at the end which leads to a violation of the
`extended-description-contains-empty-paragraph` debian policy.

This commit fixes the above behaviour.

Fixes: #20763

Modules/Internal/CPack/CPackDeb.cmake

@@ -83,6 +83,16 @@ function(cpack_deb_format_package_description TEXT OUTPUT_VAR)
   string(REPLACE "\n" ";" _lines "${_text}")
   list(POP_FRONT _lines _summary)
 
+  # If the description ends with a newline (e.g. typically if it was read
+  # from a file) the last line will be empty. We drop it here, otherwise
+  # it would be replaced by a `.` which would lead to the package violating
+  # the extended-description-contains-empty-paragraph debian policy
+  list(POP_BACK _lines _last_line)
+  string(STRIP "${_last_line}" _last_line_strip)
+  if(_last_line_strip)
+    list(APPEND _lines "${_last_line_strip}")
+  endif()
+
   # Check if reformatting required
   cpack_deb_check_description("${_summary}" "${_lines}" _result)
   if(_result)

Tests/CPackComponentsDEB/MyLibCPackConfig-components-description1.cmake.in

@@ -16,7 +16,7 @@ set(CPACK_COMPONENTS_IGNORE_GROUPS 1)
 
 # overriding previous descriptions
 set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "main description") # This become a summary line (the first one) of all descriptions
-set(CPACK_COMPONENT_APPLICATIONS_DESCRIPTION "applications_description")
+set(CPACK_COMPONENT_APPLICATIONS_DESCRIPTION "applications_description\n")
 set(CPACK_COMPONENT_HEADERS_DESCRIPTION "headers_description")
 # libraries does not have any description and should inherit from CPACK_PACKAGE_DESCRIPTION_SUMMARY
 # plus content of the `CPACK_PACKAGE_DESCRIPTION_FILE`.

Tests/RunCMake/CPack/tests/DEB_DESCRIPTION/VerifyResult.cmake

@@ -46,17 +46,7 @@ set(_expected_description [[ Description: This is the summary line
   .
   See also: https://www.debian.org/doc/debian-policy/ch-controlfields.html#description]])
 
-# ATTENTION The code in `cmCPackGenerator.cxx` to read `CPACK_PACKAGE_DESCRIPTION_FILE`
-# has a BUG: it appends the `\n` character to every line of the
-# input, even if there was no EOL (e.g. at the last line of the file).
-# That is WHY for this sub-test the one more pre-formatted "empty"
-# line required!
-# NOTE For component based installers content of the file gonna read by
-# `CPackDeb` module and the `file(READ...)` command so no the mentioned
-# workaround required!
-if(RunCMake_SUBTEST_SUFFIX STREQUAL "CPACK_PACKAGE_DESCRIPTION_FILE" AND PACKAGING_TYPE STREQUAL "MONOLITHIC")
-  string(APPEND _expected_description "\n  ." )
-elseif(RunCMake_SUBTEST_SUFFIX STREQUAL "CPACK_NO_PACKAGE_DESCRIPTION")
+if(RunCMake_SUBTEST_SUFFIX STREQUAL "CPACK_NO_PACKAGE_DESCRIPTION")
   set(_expected_description [[ Description: This is the summary line]])
 elseif(RunCMake_SUBTEST_SUFFIX STREQUAL "CPACK_COMPONENT_COMP_DESCRIPTION")
   set(_expected_description [[ Description: One line description]])