shields: scripts: cmake: use list_shields.py in shields.cmake

The logic to "guess" shield names/dirs was duplicated between
list_shields.py (which is used by e.g. west shields) and shields.cmake.
This commit moves the logic to list_shields.py, and updates
shields.cmake to call the script and process its JSON output.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

cmake/modules/shields.cmake

@@ -31,6 +31,7 @@
 include_guard(GLOBAL)
 
 include(extensions)
+include(python)
 
 # Check that SHIELD has not changed.
 zephyr_check_cache(SHIELD WATCH)
@@ -46,31 +47,42 @@ endif()
 # After processing all shields, only invalid shields will be left in this list.
 set(SHIELD-NOTFOUND ${SHIELD_AS_LIST})
 
-foreach(root ${BOARD_ROOT})
-  set(shield_dir ${root}/boards/shields)
-  # Match the Kconfig.shield files in the shield directories to make sure we are
-  # finding shields, e.g. x_nucleo_iks01a1/Kconfig.shield
-  file(GLOB_RECURSE shields_refs_list ${shield_dir}/*/Kconfig.shield)
-
-  # The above gives a list of Kconfig.shield files, like this:
-  #
-  # x_nucleo_iks01a1/Kconfig.shield;x_nucleo_iks01a2/Kconfig.shield
-  #
-  # we construct a list of shield names by extracting the directories
-  # from each file and looking for <shield>.overlay files in there.
-  # Each overlay corresponds to a shield. We obtain the shield name by
-  # removing the .overlay extension.
-  # We also create a SHIELD_DIR_${name} variable for each shield's directory.
-  foreach(shields_refs ${shields_refs_list})
-    get_filename_component(shield_path ${shields_refs} DIRECTORY)
-    file(GLOB shield_overlays RELATIVE ${shield_path} ${shield_path}/*.overlay)
-    foreach(overlay ${shield_overlays})
-      get_filename_component(shield ${overlay} NAME_WE)
-      list(APPEND SHIELD_LIST ${shield})
-      set(SHIELD_DIR_${shield} ${shield_path})
-    endforeach()
+# Prepare list shields command.
+# This command is used for locating the shield dir as well as printing all shields
+# in the system in the following cases:
+# - User specifies an invalid SHIELD
+# - User invokes '<build-command> shields' target
+list(TRANSFORM BOARD_ROOT PREPEND "--board-root=" OUTPUT_VARIABLE board_root_args)
+
+set(list_shields_commands
+  COMMAND ${PYTHON_EXECUTABLE} ${ZEPHYR_BASE}/scripts/list_shields.py
+  ${board_root_args} --json
+)
+
+# Get list of shields in JSON format
+execute_process(${list_shields_commands}
+  OUTPUT_VARIABLE shields_json
+  ERROR_VARIABLE err_shields
+  RESULT_VARIABLE ret_val
+)
+
+if(ret_val)
+  message(FATAL_ERROR "Error finding shields\nError message: ${err_shields}")
+endif()
+
+string(JSON shields_length LENGTH ${shields_json})
+
+if(shields_length GREATER 0)
+  math(EXPR shields_length "${shields_length} - 1")
+
+  foreach(i RANGE ${shields_length})
+    string(JSON shield GET "${shields_json}" "${i}")
+    string(JSON shield_name GET ${shield} name)
+    string(JSON shield_dir GET ${shield} dir)
+    list(APPEND SHIELD_LIST ${shield_name})
+    set(SHIELD_DIR_${shield_name} ${shield_dir})
   endforeach()
-endforeach()
+endif()
 
 # Process shields in-order
 if(DEFINED SHIELD)

scripts/list_shields.py

@@ -5,6 +5,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import argparse
+import json
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -57,6 +58,7 @@ def find_shields_in(root):
 def parse_args():
     parser = argparse.ArgumentParser(allow_abbrev=False)
     add_args(parser)
+    add_args_formatting(parser)
     return parser.parse_args()
 
 def add_args(parser):
@@ -66,9 +68,19 @@ def add_args(parser):
                         type=Path, action='append',
                         help='add a board root, may be given more than once')
 
+def add_args_formatting(parser):
+    parser.add_argument("--json", action='store_true',
+                        help='''output list of shields in JSON format''')
+
 def dump_shields(shields):
-    for shield in shields:
-        print(f'  {shield.name}')
+    if args.json:
+        print(
+            json.dumps([{'dir': shield.dir.as_posix(), 'name': shield.name} for shield in shields])
+        )
+    else:
+        for shield in shields:
+            print(f'  {shield.name}')
 
 if __name__ == '__main__':
-    dump_shields(find_shields(parse_args()))
+    args = parse_args()
+    dump_shields(find_shields(args))