UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0: invalid start byte

[Step2Web]

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Hi all, we would need some help regarding an issue we've been seeing in our lupa related code:

  File "lupa/_lupa.pyx", line 308, in lupa._lupa.LuaRuntime.execute
  File "lupa/_lupa.pyx", line 1324, in lupa._lupa.run_lua
  File "lupa/_lupa.pyx", line 1333, in lupa._lupa.call_lua
  File "lupa/_lupa.pyx", line 1358, in lupa._lupa.execute_lua_call
  File "lupa/_lupa.pyx", line 281, in lupa._lupa.LuaRuntime.reraise_on_exception
  File "lupa/_lupa.pyx", line 1496, in lupa._lupa.py_call_with_gil
  File "lupa/_lupa.pyx", line 1459, in lupa._lupa.call_python
  File "lupa/_lupa.pyx", line 1144, in lupa._lupa.py_from_lua
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0: invalid start byte
'utf-8' codec can't decode byte 0x80 in position 0: invalid start byte

From what he have seen, this happens when the lua code calls a python function after having used string.sub on a string containing ’ (byte 153) or "”" (byte 226).

I've built a minimal repo that reproduces the issue: https://github.com/Step2Web/lupa-encoding-issue

We'd greatly appreciate some help in how to resolve this. Thank you in advance and please let me know if there's any other information you'll need.

[Step2Web]

Quick update here, I'm convinced now that this is actually a bug in Lua in how Unicode characters are handled. And using sub, we're splitting the unicode character, which breaks decoding in python later on.

[Le0Developer]

Minimal reproduction: lua.eval('("’"):sub(1,1)')

[Le0Developer]

´ is a compound and represented by multiple bytes.

string.sub ignores compounds and only takes the literal byte, which by itself are not valid UTF-8 (byte 153 or 226 are not valid).

You can set encoding=None when creating the LuaRuntime to disable decoding and get bytes instead.