solidity compiler settings in project.json don't work as expected

[voith]

• Populus Version: on master
• OS: OSx

What was wrong?

providing any command_line option like evm_version in the example below doesn't work

"SolcAutoBackend": {
        "class": "populus.compilation.backends.SolcAutoBackend",
        "settings": {
          "optimize": true,
          "command_line_options": {
            "allow_paths": "/",
            "evm_version": "homestead"
          }
}

This is because populus uses standard-json as input to py-solc:

populus/populus/compilation/backends/solc_standard_json.py

Lines 134 to 145 in c256cba

	std_input = {
	'language': 'Solidity',
	'sources': sources,
	'settings': {
	'remappings': import_remappings,
	'outputSelection': {
	'*': {
	'*': REQUIRED_OUTPUT_SELECTION
	}
	}
	}
	}

Whenever standard-json is passed to py-solc all other options are ignored.

$solc --help
...
 --standard-json      Switch to Standard JSON input / output mode, ignoring
                       all options. It reads from standard input and provides
                       the result on the standard output.
...

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[voith]

However, populus provides another way to configure settings in standard-json. Use stdin instead of command_line_options

"SolcAutoBackend": {
        "class": "populus.compilation.backends.SolcAutoBackend",
        "settings": {
          "optimize": true,
          "output_values": [
            "abi",
            "bin",
            "bin-runtime",
            "metadata"
          ],
          "command_line_options": {
            "allow_paths": "/"
          },
          "stdin": {
            "evmVersion": "homestead"
          }
}

However, allow_paths seems to work for some reason.