cmake: extensions: Improve import_kconfig() bool/tristate parsing

This function has been working fine for parsing Kconfig fragments as
processed by Kconfiglib, but it can be made more robust for parsing
fragments from other sources, including handwritten ones.

Previously, Kconfig fragment lines of the form `# CONFIG_FOO is not set`
were ignored entirely, while lines of the form `CONFIG_FOO=n` would set
the corresponding CMake variable or target property to a literal `n`.
However, Kconfiglib treats both equivalently - as assignments to `n` -
so `import_kconfig()` should too.

Due to the fact that `.config` files output by Kconfiglib always show
disabled options as `# CONFIG_FOO is not set` (which was being ignored),
existing CMake code expects `CONFIG_FOO` to be unset. To avoid breakage,
the variable/property will now be unset explicitly by `import_kconfig()`
when it encounters either representation of `CONFIG_FOO=n`.

Moreover, for bool and tristate symbols, Kconfiglib accepts assignments
like `CONFIG_FOO=yeah`, `CONFIG_FOO=maybe`, or `CONFIG_FOO=nope`, and it
transforms the value of `CONFIG_FOO` into `y`, `m`, or `n` respectively.
This effect is now replicated in CMake.

Signed-off-by: Grzegorz Swiderski <[email protected]>

Author: 57300

cmake/modules/extensions.cmake

@@ -1552,40 +1552,62 @@ endfunction()
 #                     CMake namespace.
 function(import_kconfig prefix kconfig_fragment)
   cmake_parse_arguments(IMPORT_KCONFIG "" "TARGET" "" ${ARGN})
-  # Parse the lines prefixed with 'prefix' in ${kconfig_fragment}
   file(
     STRINGS
     ${kconfig_fragment}
     DOT_CONFIG_LIST
-    REGEX "^${prefix}"
     ENCODING "UTF-8"
   )
 
-  foreach (CONFIG ${DOT_CONFIG_LIST})
-    # CONFIG could look like: CONFIG_NET_BUF=y
-
-    # Match the first part, the variable name
-    string(REGEX MATCH "[^=]+" CONF_VARIABLE_NAME ${CONFIG})
+  foreach (LINE ${DOT_CONFIG_LIST})
+    if("${LINE}" MATCHES "^(${prefix}[^=]+)=([ymn]|.+$)")
+      # Matched a normal value assignment, like: CONFIG_NET_BUF=y
+      # Note: if the value starts with 'y', 'm', or 'n', then we assume it's a
+      # bool or tristate (we don't know the type from <kconfig_fragment> alone)
+      # and we only match the first character. This is to align with Kconfiglib.
+      set(CONF_VARIABLE_NAME "${CMAKE_MATCH_1}")
+      set(CONF_VARIABLE_VALUE "${CMAKE_MATCH_2}")
+    elseif("${LINE}" MATCHES "^# (${prefix}[^ ]+) is not set")
+      # Matched something like: # CONFIG_FOO is not set
+      # This is interpreted as: CONFIG_FOO=n
+      set(CONF_VARIABLE_NAME "${CMAKE_MATCH_1}")
+      set(CONF_VARIABLE_VALUE "n")
+    else()
+      # Ignore this line.
+      # Note: we also ignore assignments which don't have the desired <prefix>.
+      continue()
+    endif()
 
-    # Match the second part, variable value
-    string(REGEX MATCH "=(.+$)" CONF_VARIABLE_VALUE ${CONFIG})
-    # The variable name match we just did included the '=' symbol. To just get the
-    # part on the RHS we use match group 1
-    set(CONF_VARIABLE_VALUE ${CMAKE_MATCH_1})
+    # If the provided value is n, then the corresponding CMake variable or
+    # target property will be unset.
+    if("${CONF_VARIABLE_VALUE}" STREQUAL "n")
+      if(DEFINED IMPORT_KCONFIG_TARGET)
+        set_property(TARGET ${IMPORT_KCONFIG_TARGET} PROPERTY "${CONF_VARIABLE_NAME}")
+      else()
+        unset("${CONF_VARIABLE_NAME}" PARENT_SCOPE)
+      endif()
+      list(REMOVE_ITEM keys "${CONF_VARIABLE_NAME}")
+      continue()
+    endif()
 
-    if("${CONF_VARIABLE_VALUE}" MATCHES "^\"(.*)\"$") # Is surrounded by quotes
+    # Otherwise, the variable/property will be set to the provided value.
+    # For string values, we also remove the surrounding quotation marks.
+    if("${CONF_VARIABLE_VALUE}" MATCHES "^\"(.*)\"$")
       set(CONF_VARIABLE_VALUE ${CMAKE_MATCH_1})
     endif()
 
     if(DEFINED IMPORT_KCONFIG_TARGET)
-      set_property(TARGET ${IMPORT_KCONFIG_TARGET} APPEND PROPERTY "kconfigs" "${CONF_VARIABLE_NAME}")
       set_property(TARGET ${IMPORT_KCONFIG_TARGET} PROPERTY "${CONF_VARIABLE_NAME}" "${CONF_VARIABLE_VALUE}")
     else()
       set("${CONF_VARIABLE_NAME}" "${CONF_VARIABLE_VALUE}" PARENT_SCOPE)
     endif()
     list(APPEND keys "${CONF_VARIABLE_NAME}")
   endforeach()
 
+  if(DEFINED IMPORT_KCONFIG_TARGET)
+    set_property(TARGET ${IMPORT_KCONFIG_TARGET} PROPERTY "kconfigs" "${keys}")
+  endif()
+
   list(LENGTH IMPORT_KCONFIG_UNPARSED_ARGUMENTS unparsed_length)
   if(unparsed_length GREATER 0)
     if(unparsed_length GREATER 1)