fix(merge_bin): treat files starting with colon as raw files

esptool/bin_image.py

@@ -13,7 +13,7 @@ import struct
 import tempfile
 from typing import BinaryIO, Optional
 
-from intelhex import IntelHex
+from intelhex import HexRecordError, IntelHex
 
 from .loader import ESPLoader
 from .targets import (
@@ -47,6 +47,7 @@ def intel_hex_to_bin(file: BinaryIO, start_addr: Optional[int] = None) -> Binary
     INTEL_HEX_MAGIC = b":"
     magic = file.read(1)
     file.seek(0)
+    try:
         if magic == INTEL_HEX_MAGIC:
             ih = IntelHex()
             ih.loadhex(file.name)
@@ -56,6 +57,9 @@ def intel_hex_to_bin(file: BinaryIO, start_addr: Optional[int] = None) -> Binary
             return bin
         else:
             return file
+    except HexRecordError:
+        # file started with HEX magic but the rest was not according to the standard
+        return file
 
 
 def LoadFirmwareImage(chip, image_file):

test/test_merge_bin.py

@@ -263,6 +263,16 @@ class TestMergeBin:
         # verify the file itself
         assert source == merged_bin[0x1000:]
 
+    def test_hex_header_raw_file(self):
+        # use raw binary file starting with colon
+        with tempfile.NamedTemporaryFile(delete=False) as f:
+            f.write(b":")
+        try:
+            merged = self.run_merge_bin("esp32", [(0x0, f.name)])
+            assert merged == b":"
+        finally:
+            os.unlink(f.name)
+
 
 class UF2Block(object):
     def __init__(self, bs):