Not obvious compilation error in Slither

[disconnect3d]

Running slither <contract id> when we don't have proper solc version installed via solc-select may result in an unambiguous error of Invalid solc compilation which does not describe what shall we do.

Example:

$ slither 0xB8c77482e45F1F44dE1745F52C74426C631bDD52
Expecting value: line 1 column 1 (char 0)
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/solc.py", line 412, in _run_solc
    ret = json.loads(stdout)
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/slither/__main__.py", line 721, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/usr/local/lib/python3.6/dist-packages/slither/__main__.py", line 71, in process_all
    compilations = compile_all(target, **vars(args))
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 1076, in compile_all
    compilations.append(CryticCompile(target, **kwargs))
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 137, in __init__
    self._compile(**kwargs)
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 987, in _compile
    self._platform.compile(self, **kwargs)
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/etherscan.py", line 273, in compile
    working_dir=working_dir,
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/solc.py", line 417, in _run_solc
    raise InvalidCompilation(f"Invalid solc compilation {stderr}")
crytic_compile.platform.exceptions.InvalidCompilation: Invalid solc compilation
ERROR:root:None
ERROR:root:Error in 0xB8c77482e45F1F44dE1745F52C74426C631bDD52
ERROR:root:Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/solc.py", line 412, in _run_solc
    ret = json.loads(stdout)
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/slither/__main__.py", line 721, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/usr/local/lib/python3.6/dist-packages/slither/__main__.py", line 71, in process_all
    compilations = compile_all(target, **vars(args))
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 1076, in compile_all
    compilations.append(CryticCompile(target, **kwargs))
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 137, in __init__
    self._compile(**kwargs)
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/crytic_compile.py", line 987, in _compile
    self._platform.compile(self, **kwargs)
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/etherscan.py", line 273, in compile
    working_dir=working_dir,
  File "/usr/local/lib/python3.6/dist-packages/crytic_compile/platform/solc.py", line 417, in _run_solc
    raise InvalidCompilation(f"Invalid solc compilation {stderr}")
crytic_compile.platform.exceptions.InvalidCompilation: Invalid solc compilation

I investigated that by adding additional prints of stdout/stderr and process.returncode in

crytic-compile/crytic_compile/platform/solc.py

Lines 402 to 409 in d99e5a7

	stdout, stderr = process.communicate()
	stdout, stderr = (stdout.decode(), stderr.decode()) # convert bytestrings to unicode strings
	if stderr and (not solc_disable_warnings):
	LOGGER.info("Compilation warnings/errors on %s:\n%s", filename, stderr)
	try:
	ret = json.loads(stdout)

It turns out that the information that solc is not installed is printed out on stdout and so is not passed further to the user:

STDOUT: Version '0.4.12' not installed (set by SOLC_VERSION). Run `solc-select install 0.4.12`.
STDERR:
RETCODE 1

I think we should either make solc-select to print info on stdout, or, make crytic-compile to take such stdout into account, or, make so it respects return code? I didn't check that but shouldn't return code be a good indicator whether the command succeeded?

[montyly]

I think this is a good idea. However, it should be done when we will refactor our solc-select integration to use the new python version (#157)

[0xalpharush]

We improved this in #353