Tools - upload.py exception handling fixes (#9186)

- don't check exc_info() in `finally`, it only works without `except` with just `try` and `finally`
  see https://docs.python.org/3/reference/compound_stmts.html#try
  after `except Exception as e:` block, `e` is already deleted

- handle a rare case when esptool code does not close 'erase_file'.
  printing paths may cause encoding issues, so just fall through silently

- simplify ordering of write_flash & erase_region arguments
  since we always end up in write_flash, prefer to think of it as argument pairs 'addr' + 'path'. actual binaries go first, erase 
  temporaries go last. construct write args beforehand and apply when finishing with the command line.

  both commands can appear multiple times, for manual or scripting cases, where multiple regions should be erased / written to

tools/upload.py

@@ -1,74 +1,126 @@
 #!/usr/bin/env python3
 
 # Wrapper for Arduino core / others that can call esptool.py possibly multiple times
-# Adds pyserial to sys.path automatically based on the path of the current file
-
-# First parameter is pyserial path, second is esptool path, then a series of command arguments
-# i.e. upload.py tools/pyserial tools/esptool write_flash file 0x0
+# Adds pyserial & esptool that are in the same directory as the script to sys.path
 
 import os
+import atexit
+import pathlib
 import sys
 import tempfile
+import traceback
 
-sys.argv.pop(0) # Remove executable name
-toolspath = os.path.dirname(os.path.realpath(__file__))
+from typing import List
+
+# Add neighbouring pyserial & esptool to search path
+MODULES = [
+    "pyserial",
+    "esptool",
+]
+
+PWD = pathlib.Path(__file__).resolve().parent
+for m in MODULES:
+    sys.path.insert(0, (PWD / m).as_posix())
+
+# If this fails, we can't continue and will bomb below
 try:
-    sys.path.insert(0, os.path.join(toolspath, "pyserial")) # Add pyserial dir to search path
-    sys.path.insert(0, os.path.join(toolspath, "esptool")) # Add esptool dir to search path
-    import esptool # If this fails, we can't continue and will bomb below
+    import esptool
 except ImportError:
-    sys.stderr.write("pyserial or esptool directories not found next to this upload.py tool.\n")
+    sys.stderr.write(
+        "\n*** pyserial or esptool directories not found next to upload.py tool (this script) ***\n"
+    )
+    traceback.print_exc(file=sys.stderr)
+    sys.stderr.flush()
+
     sys.exit(1)
 
-cmdline = []
-write_option = ''
-write_addr = '0x0'
-erase_addr = ''
-erase_len = ''
 
-while sys.argv:
-    thisarg = sys.argv.pop(0)
+def make_erase_pair(addr: str, dest_size: int, block_size=2**16):
+    dest, path = tempfile.mkstemp()
 
-    # We silently replace the 921kbaud setting with 460k to enable backward
+    buffer = bytearray(b"\xff" * block_size)
+    while dest_size:
+        remainder = dest_size % block_size
+
+        if remainder:
+            src = buffer[:remainder]
+            src_size = remainder
+        else:
+            src = buffer
+            src_size = block_size
+
+        os.write(dest, src)
+        dest_size -= src_size
+
+    os.close(dest)
+
+    def maybe_remove(path):
+        try:
+            os.remove(path)
+        except Exception:
+            pass
+
+    atexit.register(maybe_remove, path)
+    return [addr, path]
+
+
+argv = sys.argv[1:]  # Remove executable name
+
+cmdline: List[str] = []
+write_options: List[str] = ["--flash_size", "detect"]
+erase_options: List[str] = []
+
+thisarg = ""
+lastarg = ""
+while argv:
+    lastarg = thisarg
+    thisarg = argv.pop(0)
+
+    # We silently replace the high-speed setting with 460k to enable backward
     # compatibility with the old esptool-ck.exe.  Esptool.py doesn't seem
-    # work reliably at 921k, but is still significantly faster at 460kbaud.
-    if thisarg == "921600":
+    # work reliably, but 460kbaud is still plenty fast.
+    if lastarg == "--baud" and thisarg in ("921600", "3000000"):
         thisarg = "460800"
 
     # 'erase_flash' command is translated to the write_flash --erase-all option
     # https://github.com/esp8266/Arduino/issues/6755#issuecomment-553208688
     if thisarg == "erase_flash":
-        write_option = '--erase-all'
-    elif thisarg == 'erase_region':
-        erase_addr = sys.argv.pop(0)
-        erase_len = sys.argv.pop(0)
-    elif thisarg == 'write_flash':
-        write_addr = sys.argv.pop(0)
-        binary = sys.argv.pop(0)
+        write_options.append("--erase-all")
+
+    # instead of providing esptool with separate targets,
+    # everything below becomes 'write_flash' [<addr> <path>] pairs
+
+    # 'erase_region' becomes a temporary file filled with 0xff
+    # this pair is appended *after* 'write_flash' pairs
+    elif thisarg == "erase_region":
+        addr = argv.pop(0)
+        size = int(argv.pop(0), 0)
+        erase_options.extend(make_erase_pair(addr, size))
+
+    # 'write_flash' pair taken in order it was specified
+    elif thisarg == "write_flash":
+        addr = argv.pop(0)
+        path = argv.pop(0)
+        write_options.extend([addr, path])
+
+    # everything else is used as-is
     elif thisarg:
-        cmdline = cmdline + [thisarg]
+        cmdline.append(thisarg)
 
-cmdline = cmdline + ['write_flash']
-if write_option:
-    cmdline = cmdline + [write_option]
-cmdline = cmdline + ['--flash_size', 'detect']
-cmdline = cmdline + [write_addr, binary]
 
-erase_file = ''
-if erase_addr:
-    # Generate temporary empty (0xff) file
-    eraser = tempfile.mkstemp()
-    erase_file = eraser[1]
-    os.write(eraser[0], bytearray([0xff] * int(erase_len, 0)))
-    os.close(eraser[0])
-    cmdline = cmdline + [erase_addr, erase_file]
+cmdline.append("write_flash")
+for opts in (write_options, erase_options):
+    if opts:
+        cmdline.extend(opts)
 
 try:
     esptool.main(cmdline)
-except Exception as e:
-    sys.stderr.write('\nA fatal esptool.py error occurred: %s' % e)
-finally:
-    if erase_file:
-        os.remove(erase_file)
-    if any(sys.exc_info()):
-        sys.exit(2)
+except Exception:
+    etype, evalue, _ = sys.exc_info()
+    estring = "\n".join(traceback.format_exception_only(etype, value=evalue))
+
+    sys.stderr.write("\n*** upload.py fatal error ***\n")
+    sys.stderr.write(estring)
+    sys.stderr.flush()
+
+    sys.exit(2)