refactor(readline): better FindReadline module

The readline library is now searched with pkg-config first.
If pkg-config is not installed, the search is manual.
In both cases, the Readline::readline target is created,
embedding transitive requirements.

FindReadline module was written with the help of Le Chat AI (https://chat.mistral.ai/chat)

Author: aollier

cmake/FindReadline.cmake

@@ -1,49 +1,88 @@
-# Code copied from sethhall@github
+#.rst:
+# FindReadline
+# ------------
 #
-# - Try to find readline include dirs and libraries
+# Find the readline library.
 #
 # Usage of this module as follows:
 #
-#     find_package(Readline)
+#     find_package(Readline [REQUIRED] [QUIET])
+#     target_link_libraries(<target> PRIVATE Readline::readline)
 #
-# Variables used by this module, they can change the default behaviour and need
-# to be set before calling find_package:
+# Variables used by this module:
 #
-#  Readline_ROOT_DIR         Set this variable to the root installation of
-#                            readline if the module has problems finding the
-#                            proper installation path.
+#   Readline_ROOT              - Root directory to search for readline (e.g., /usr/local or the vcpkg installation path).
+#                               If not set, the module will search in standard system paths.
 #
-# Variables defined by this module:
+# Imported Targets
+# ^^^^^^^^^^^^^^^
 #
-#  READLINE_FOUND            System has readline, include and lib dirs found
-#  Readline_INCLUDE_DIR      The readline include directories.
-#  Readline_LIBRARY          The readline library.
+# This module defines the following :prop_tgt:`IMPORTED` target:
+#
+# ``Readline::readline``
+#   The readline library, if found.
+#
+# Result Variables
+# ^^^^^^^^^^^^^^
+#
+# ``Readline_FOUND``           - True if readline is found.
+# ``Readline_INCLUDE_DIRS``    - The readline include directories.
+# ``Readline_LIBRARIES``      - The readline libraries.
 
-find_path(Readline_ROOT_DIR
-    NAMES include/readline/readline.h
-)
+# --- Step 1: Try pkg-config first ---
+find_package(PkgConfig)
+if(PkgConfig_FOUND)
+    pkg_check_modules(Readline IMPORTED_TARGET readline)
+    if(Readline_FOUND)
+        # pkg-config found readline
+        add_library(Readline::readline ALIAS PkgConfig::Readline)
+        return()
+    endif()
+endif()
+
+# --- Step 2: Manual search if pkg-config fails ---
+# Uses Readline_ROOT if defined (CMake convention: <PackageName>_ROOT)
+set(_Readline_SEARCH_PATHS)
+if(Readline_ROOT)
+    list(APPEND _Readline_SEARCH_PATHS "${Readline_ROOT}")
+endif()
 
 find_path(Readline_INCLUDE_DIR
-    NAMES readline/readline.h
-    HINTS ${Readline_ROOT_DIR}/include
+        NAMES readline/readline.h
+        PATHS ${_Readline_SEARCH_PATHS}
+        PATH_SUFFIXES include
+        DOC "readline include directory"
 )
 
 find_library(Readline_LIBRARY
-    NAMES readline
-    HINTS ${Readline_ROOT_DIR}/lib
+        NAMES readline
+        PATHS ${_Readline_SEARCH_PATHS}
+        PATH_SUFFIXES lib lib64
+        DOC "readline library"
+)
+
+# Managing results with FindPackageHandleStandardArgs
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Readline
+        DEFAULT_MSG Readline_INCLUDE_DIR Readline_LIBRARY
 )
 
-if(Readline_INCLUDE_DIR AND Readline_LIBRARY AND Ncurses_LIBRARY)
-  set(READLINE_FOUND TRUE)
-else(Readline_INCLUDE_DIR AND Readline_LIBRARY AND Ncurses_LIBRARY)
-  find_library(Readline_LIBRARY NAMES readline)
-  include(FindPackageHandleStandardArgs)
-  find_package_handle_standard_args(Readline DEFAULT_MSG Readline_INCLUDE_DIR Readline_LIBRARY )
-  mark_as_advanced(Readline_INCLUDE_DIR Readline_LIBRARY)
-endif(Readline_INCLUDE_DIR AND Readline_LIBRARY AND Ncurses_LIBRARY)
+if(Readline_FOUND)
+    set(Readline_INCLUDE_DIRS ${Readline_INCLUDE_DIR})
+    set(Readline_LIBRARIES ${Readline_LIBRARY})
+
+    if(NOT TARGET Readline::readline)
+        add_library(Readline::readline UNKNOWN IMPORTED)
+        set_target_properties(Readline::readline PROPERTIES
+                IMPORTED_LOCATION "${Readline_LIBRARY}"
+                INTERFACE_INCLUDE_DIRECTORIES "${Readline_INCLUDE_DIRS}"
+        )
+    endif()
+endif()
 
+# Hide internal variables
 mark_as_advanced(
-    Readline_ROOT_DIR
-    Readline_INCLUDE_DIR
-    Readline_LIBRARY
+        Readline_INCLUDE_DIR
+        Readline_LIBRARY
+        Readline_ROOT
 )

src/cli/CMakeLists.txt

@@ -21,9 +21,9 @@ target_link_libraries(text_stream PUBLIC Qt6::Core)
 add_library(line_reader STATIC LineReader.cpp)
 target_link_libraries(line_reader PUBLIC Qt6::Core)
 find_package(Readline MODULE)
-if(READLINE_FOUND)
+if(Readline_FOUND)
     target_compile_definitions(line_reader PRIVATE "USE_READLINE")
-    target_link_libraries(line_reader PRIVATE ${Readline_LIBRARY})
+    target_link_libraries(line_reader PRIVATE Readline::readline)
 else()
     target_link_libraries(line_reader PRIVATE text_stream)
 endif()