CPack/DEB: Append .deb to CPACK_DEBIAN_FILE_NAME if missing

Previously we issued an error when the `.deb` or `.ipk` suffix
is missing. Instead, append the suffix `.deb` automatically.
This matches the behavior of `CPACK_ARCHIVE_FILE_NAME`, to
which the archive format suffix is automatically appended.

Help/cpack_gen/deb.rst

@@ -82,8 +82,13 @@ List of CPack DEB generator specific variables:
    Duplicate files get overwritten and it is up to the packager to set
    the variables in a manner that will prevent such errors.
 
- ``<file-name>.deb``
+ ``<file-name>[.deb]``
-   Use the given file name.  The ``.deb`` suffix is required.
+   Use the given file name.
+
+   .. versionchanged:: 3.29
+
+     The ``.deb`` suffix will be automatically added if the file name does
+     not end in ``.deb`` or ``.ipk``.  Previously the suffix was required.
 
  ``<file-name>.ipk``
    .. versionadded:: 3.10

Help/release/dev/cpack-auto-suffixes.rst

@@ -0,0 +1,6 @@
+cpack-auto-suffixes
+-------------------
+
+* The :cpack_gen:`CPack DEB Generator` :variable:`CPACK_DEBIAN_FILE_NAME`
+  variable may now be set without any suffix, and the ``.deb`` suffix
+  will be added automatically.

Modules/Internal/CPack/CPackDeb.cmake

@@ -710,7 +710,7 @@ function(cpack_deb_prepare_package_vars)
         "${CPACK_DEBIAN_PACKAGE_NAME}-dbgsym_${CPACK_DEBIAN_PACKAGE_VERSION}_${CPACK_DEBIAN_PACKAGE_ARCHITECTURE}.ddeb")
     else()
       if(NOT CPACK_DEBIAN_FILE_NAME MATCHES ".*\\.(deb|ipk)")
-        message(FATAL_ERROR "'${CPACK_DEBIAN_FILE_NAME}' is not a valid DEB package file name as it must end with '.deb' or '.ipk'!")
+        set(CPACK_DEBIAN_FILE_NAME "${CPACK_DEBIAN_FILE_NAME}.deb")
       endif()
 
       set(CPACK_OUTPUT_FILE_NAME "${CPACK_DEBIAN_FILE_NAME}")

Tests/RunCMake/CMakeLists.txt

@@ -959,6 +959,7 @@ if("${CMAKE_GENERATOR}" MATCHES "Make|Ninja")
 endif()
 
 set(cpack_tests
+  DEB.AUTO_SUFFIXES
   DEB.CUSTOM_NAMES
   DEB.DEBUGINFO
   DEB.DEFAULT_PERMISSIONS

Tests/RunCMake/CPack/RunCMakeTest.cmake

@@ -9,6 +9,7 @@ find_program(DEBUGEDIT debugedit)
 # run_cpack_test args: TEST_NAME "GENERATORS" RUN_CMAKE_BUILD_STEP "PACKAGING_TYPES"
 run_cpack_test(CUSTOM_BINARY_SPEC_FILE "RPM.CUSTOM_BINARY_SPEC_FILE" false "MONOLITHIC;COMPONENT")
 run_cpack_test(CUSTOM_NAMES "RPM.CUSTOM_NAMES;DEB.CUSTOM_NAMES;TGZ;DragNDrop" true "COMPONENT")
+run_cpack_test(AUTO_SUFFIXES "DEB.AUTO_SUFFIXES" false "MONOLITHIC")
 run_cpack_test(DEBUGINFO "DEB.DEBUGINFO" true "COMPONENT")
 if(NOT "${DEBUGEDIT}" STREQUAL "DEBUGEDIT-NOTFOUND")
   run_cpack_test(DEBUGINFO "RPM.DEBUGINFO" true "COMPONENT")

Tests/RunCMake/CPack/tests/AUTO_SUFFIXES/ExpectedFiles.cmake

@@ -0,0 +1,8 @@
+set(EXPECTED_FILES_COUNT "1")
+set(EXPECTED_FILES_NAME_GENERATOR_SPECIFIC_FORMAT TRUE)
+set(EXPECTED_FILE_CONTENT_1_LIST "/foo;/foo/CMakeLists.txt")
+
+if(GENERATOR_TYPE STREQUAL "DEB")
+  string(TOLOWER "${GENERATOR_TYPE}" file_extension_)
+  set(EXPECTED_FILE_1 "autosuffixpackage.${file_extension_}")
+endif()

Tests/RunCMake/CPack/tests/AUTO_SUFFIXES/test.cmake

@@ -0,0 +1,4 @@
+install(FILES CMakeLists.txt DESTINATION foo COMPONENT test)
+
+# if the filename doesn't have the expected deb suffix, test that it is appended automatically
+set(CPACK_DEBIAN_FILE_NAME "autosuffixpackage")