fix: display correct help in the idf_size.py wrapper

Currently the wrapper tries to figure out which version of
the esp-idf-size should be started. The legacy version is
used if explicitly requested by the -l/--legacy option or
if json format is specified. This works fine, but if help
is requested, it is printed for the wrapper as shown bellow

$ idf_size.py -h
usage: idf_size.py [-h] [--format FORMAT] [-l]

options:
  -h, --help       show this help message and exit
  --format FORMAT
  -l, --legacy

This is not convenient and the full help from the underlying
version should be displayed.

Fix this by only peeking into the args to figure out if legacy or
refactored version should be started and always spawn the underlying
esp_idf_size python module. This is done by using exit_on_error=False and
add_help=False for the ArgumentParser. When help for refactored version
is requested a note as following is printed to notify users that the
legacy version can still be used.

$ idf_size.py -h
Note: legacy esp_idf_size version can be invoked by specifying the -l/--legacy
option or by setting the ESP_IDF_SIZE_LEGACY environment variable.

Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>

Author: fhrbata

tools/idf_size.py

@@ -1,32 +1,40 @@
 #!/usr/bin/env python
 #
-# SPDX-FileCopyrightText: 2017-2023 Espressif Systems (Shanghai) CO LTD
+# SPDX-FileCopyrightText: 2017-2024 Espressif Systems (Shanghai) CO LTD
 #
 # SPDX-License-Identifier: Apache-2.0
 #
-
 import argparse
 import os
 import subprocess
 import sys
 
 if __name__ == '__main__':
-    parser = argparse.ArgumentParser()
+    # Here the argparse is used only to "peek" into arguments if
+    # legacy version is requested or if old json format is specified.
+    # In these two cases the esp_idf_size legacy version is spawned.
+    parser = argparse.ArgumentParser(exit_on_error=False, add_help=False)
     parser.add_argument('--format')
     parser.add_argument('-l', '--legacy', action='store_true', default=os.environ.get('ESP_IDF_SIZE_LEGACY', '0') == '1')
+
+    # The sys.argv is parsed with "exit_on_error", but the argparse.ArgumentError
+    # exception should never occur, because unknown args should be put into
+    # the rest variable, since the parse_known_args() method is used.
     args, rest = parser.parse_known_args()
 
     if not args.legacy and args.format != 'json':
+        # By default start the refactored version, unless legacy version is explicitly requested with
+        # -l/--legacy option or if old json format is specified.
         try:
             import esp_idf_size.ng  # noqa: F401
         except ImportError:
             print('warning: refactored esp-idf-size not installed, using legacy mode', file=sys.stderr)
             args.legacy = True
         else:
             os.environ['ESP_IDF_SIZE_NG'] = '1'
-
-    if args.legacy and args.format in ['json2', 'raw', 'tree']:
-        sys.exit(f'Legacy esp-idf-size does not support {args.format} format')
+            if not rest or '-h' in rest or '--help' in rest:
+                print(('Note: legacy esp_idf_size version can be invoked by specifying the -l/--legacy '
+                       'option or by setting the ESP_IDF_SIZE_LEGACY environment variable.'))
 
     if args.format is not None:
         rest = ['--format', args.format] + rest