Standard JSON compilation cannot find or read files.

[pipermerriam]

The compiler throws an error when trying to compile using the --standard-json flag when reading from a file.

echo '{"language": "Solidity", "sources": {"Greeter.sol": {"urls": ["file:///Users/piper/sites/py-solc/tmp/Greeter.sol"]}}}' | solc --standard-json
{"contracts":{},"errors":[{"component":"general","formattedMessage":"Cannot import url (\"file:///Users/piper/sites/py-solc/tmp/Greeter.sol\"): Unknown exception in read callback.","message":"Cannot import url (\"file:///Users/piper/sites/py-solc/tmp/Greeter.sol\"): Unknown exception in read callback.","severity":"error","type":"IOError"}],"sources":{}}

I've also tried the following formats for the file path just in case I was formatting something a little wrong:

• file:///Users/piper/sites/py-solc/tmp/Greeter.sol
• file://Users/piper/sites/py-solc/tmp/Greeter.sol
• file://tmp/Greeter.sol
• file://./tmp/Greeter.sol
• tmp/Greeter.sol
• /Users/piper/sites/py-solc/tmp/Greeter.sol

Help please

[axic]

solc at the moment doesn't support URL prefixes, such as file:// (tracked in #2157), but using it in for example browser-solidity should be possible.

For regular paths, the paths must first be whitelisted via --allow-paths <path1>,<path2>,... So for your use case, it should be echo .. | solc --allow-paths tmp --standard-json.

Also --allow-paths cannot handle trailing forward slashes yet (see #2147).

[pipermerriam]

That got things working, though I had to use absolute paths for everything as I wasn't able to get any form of relative path to work for either the allow-paths value or the paths passed in via standard json.

[MicahZoltu]

Workaround is to provide an absolute path to to some ancestor directory as an --allow-paths parameter and then include a full path to the file as one of the urls in --standard-json.

echo '{"language": "Solidity", "sources": { "file.sol": { "urls": [ "/full/path/to/file.sol" ] } } }' | solc --allow-paths /full/path --standard-json