Address review: reserve_byte, varint(0), field_ifdef, getattr guard

esphome/components/api/api_pb2.cpp

@@ -2333,7 +2333,8 @@ uint8_t *BluetoothLERawAdvertisementsResponse::encode(ProtoWriteBuffer &buffer P
   for (uint16_t i = 0; i < this->advertisements_len; i++) {
     auto &sub_msg = this->advertisements[i];
     ProtoEncode::write_raw_byte(pos PROTO_ENCODE_DEBUG_ARG, 10);
-    uint8_t *len_pos = pos++;
+    uint8_t *len_pos = pos;
+    ProtoEncode::reserve_byte(pos PROTO_ENCODE_DEBUG_ARG);
     ProtoEncode::write_raw_byte(pos PROTO_ENCODE_DEBUG_ARG, 8);
     ProtoEncode::encode_varint_raw_64(pos PROTO_ENCODE_DEBUG_ARG, sub_msg.address);
     ProtoEncode::write_raw_byte(pos PROTO_ENCODE_DEBUG_ARG, 16);

esphome/components/api/proto.h

@@ -352,6 +352,12 @@ class ProtoEncode {
     PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
     *pos++ = b;
   }
+  /// Reserve one byte for later backpatch (e.g., sub-message length).
+  /// Advances pos past the reserved byte without writing a value.
+  static inline void ESPHOME_ALWAYS_INLINE reserve_byte(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM) {
+    PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
+    pos++;
+  }
   /// Write raw bytes to the buffer (no tag, no length prefix).
   static inline void ESPHOME_ALWAYS_INLINE encode_raw(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
                                                       const void *data, size_t len) {

script/api_protobuf/api_protobuf.py

@@ -446,7 +446,7 @@ class TypeInfo(ABC):
 
 def _varint_max_size(bits: int) -> int:
     """Return the maximum varint encoding size for a value with the given number of bits."""
-    return (bits + 6) // 7  # ceil(bits / 7)
+    return (max(bits, 1) + 6) // 7  # ceil(bits / 7), min 1 byte for varint(0)
 
 
 TYPE_INFO: dict[int, TypeInfo] = {}
@@ -1615,7 +1615,8 @@ def _generate_inline_encode_block(
     lines = []
     lines.append(f"auto &sub_msg = {element};")
     lines.append(f"ProtoEncode::write_raw_byte(pos, {tag});")
-    lines.append("uint8_t *len_pos = pos++;")
+    lines.append("uint8_t *len_pos = pos;")
+    lines.append("ProtoEncode::reserve_byte(pos);")
 
     # Generate inline field encoding for each sub-message field
     for field in sub_desc.field:
@@ -1625,7 +1626,13 @@ def _generate_inline_encode_block(
         encode_line = ti.encode_content
         # Replace this-> with sub_msg reference for the sub-message fields
         encode_line = encode_line.replace("this->", "sub_msg.")
-        lines.extend(encode_line.split("\n"))
+        # Honor per-field ifdef guards
+        field_ifdef = (
+            get_field_opt(field, pb.field_ifdef, None)
+            if field.options.HasExtension(pb.field_ifdef)
+            else None
+        )
+        lines.extend(wrap_with_ifdef(encode_line, field_ifdef))
 
     lines.append("*len_pos = static_cast<uint8_t>(pos - len_pos - 1);")
     return "\n".join(lines)
@@ -1659,7 +1666,13 @@ def _generate_inline_size_block(
         size_line = ti.get_size_calculation(f"sub_msg.{ti.field_name}", force)
         # Replace hardcoded this-> references (e.g., FixedArrayBytesType uses this->field_len)
         size_line = size_line.replace("this->", "sub_msg.")
-        lines.extend(size_line.split("\n"))
+        # Honor per-field ifdef guards
+        field_ifdef = (
+            get_field_opt(field, pb.field_ifdef, None)
+            if field.options.HasExtension(pb.field_ifdef)
+            else None
+        )
+        lines.extend(wrap_with_ifdef(size_line, field_ifdef))
 
     return "\n".join(lines)
 
@@ -2686,16 +2699,21 @@ def build_message_type(
 
     # Check if this message uses inline_encode — if so, skip generating standalone
     # encode/calculate_size methods since the encoding is inlined into the parent.
+    inline_opt = getattr(pb, "inline_encode", None)
     is_inline_only = (
         message_id is None  # Not a service message (no id)
-        and get_opt(desc, getattr(pb, "inline_encode", None), False)
+        and inline_opt is not None
+        and get_opt(desc, inline_opt, False)
     )
 
     # Only generate encode method if this message needs encoding and has fields
     if needs_encode and encode and not is_inline_only:
         # Add PROTO_ENCODE_DEBUG_ARG after pos in all proto_* calls
         encode_debug = [
-            line.replace("(pos,", "(pos PROTO_ENCODE_DEBUG_ARG,") for line in encode
+            line.replace("(pos,", "(pos PROTO_ENCODE_DEBUG_ARG,").replace(
+                "(pos)", "(pos PROTO_ENCODE_DEBUG_ARG)"
+            )
+            for line in encode
         ]
         o = f"uint8_t *{desc.name}::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {{\n"
         o += "  uint8_t *__restrict__ pos = buffer.get_pos();\n"