nxgdb/utils: add has_field and fix ArrayIterator

1. Add method to check if an object has specified field.
2. Fix Array iterator that walrus expression should store result of the
   function, instead of the compare result.

Note that walrus operation has lowest priority except ','.

Signed-off-by: xuxingliang <xuxingliang@xiaomi.com>

tools/pynuttx/nxgdb/utils.py

@@ -441,6 +441,20 @@ def get_field(val, key, default=None):
         return default
 
 
+def has_field(obj: Union[gdb.Type, gdb.Value], key):
+    if isinstance(obj, gdb.Type):
+        t = obj
+    elif isinstance(obj, gdb.Value):
+        t = obj.type
+    else:
+        raise gdb.GdbError(f"Unsupported type {type(obj)}")
+
+    while t.code in (gdb.TYPE_CODE_PTR, gdb.TYPE_CODE_ARRAY, gdb.TYPE_CODE_TYPEDEF):
+        t = t.target()
+
+    return any(f.name == key for f in t.fields())
+
+
 def get_bytes(val, size):
     """Convert a gdb value to a bytes object"""
     try:
@@ -958,7 +972,7 @@ class ArrayIterator:
             raise gdb.error(f"Not an array: {array}, type: {array.type}")
 
         if type_code == gdb.TYPE_CODE_ARRAY:
-            if n := nitems(array) > 0:
+            if (n := nitems(array)) > 0:
                 maxlen = min(n, maxlen) if maxlen is not None else n
 
         if maxlen is None: