[CLI] Report errors for command line options that have no effect

[cameel]

Abstract

The compiler is pretty lax about command-line options whose values it does not use and just ignores many of them. It should report errors instead.

Over time we've started adding checks against this (e.g. #9075, #9364) they they're still very incomplete.

Motivation

Not getting an error when an option is invalid makes it harder for the user to realize that. It's especially problematic with options that seem to make sense together:

• --pretty-json sounds like it would affect --standard-json but it only works with --combined-json (Make --pretty-json work with Standard JSON output #11583.)
• --bin should be supported in the assembler mode but currently isn't ([CLI] Do not ignore the output selection in assembler mode #3870).

Specification

• There are several input modes (compiler, linker, assembler, standard JSON) and many options are not valid in one of these modes. The invalid ones should produce an error.
  • Take a look at tests for input modes in CommandLineParser. Basically, all options do not result in a change in CommandLineOptions in a specific mode should be invalid in that mode.
• Options that have equivalents and Standard JSON should be errors when --standard-json is used. For example:
  • Model checker settings.
  • Remappings.
  • --color/--no-color - Standard JSON output is not colorized and even when it will be (Support coloured messages in standard json #11507), this option should not affect it.
  • --libraries.
  • --error-codes.
• Please also check options whose values are not ignored by CommandLineParser but are still not used by CommandLineInterface.

Backwards Compatibility

This does not introduce any backwards-incompatible changes to the language itself but any command-line tools relying on the current behavior of options being ignored will be affected.

[Midhun07]

Hi @cameel I would like to work on this issue.
Also, Kindly point me to a good starting point. Thank you.

[cameel]

Great! There are many options so maybe it would be best to start with a PR that does this for only one of them and then, when you get the hang of it, continue with the rest in subsequent PRs. I think that --experimental-via-ir might be a good one to start with.

Start by running solc --help and looking at the option description and at the "Alternative Input Modes" section. These modes map to the InputMode enum in CommandLineParser. The only modes where the option makes sense are Compiler and CompilerWithASTImport. You can find that out by looking at solc/CommandLineInterface.cpp - there's only a single place in compile() that uses its value. In any other mode the option is ignored. The task is to modify CommandLineParser to return an error if the option is used in those other modes.

After you do this, tests in test/solc/CommandLineParser.cpp will start failing. Remove the option from them and instead add a new test case that loops over the modes where the option is invalid and checks the error message. You can use the existing no_options test case as a base.

Finally, don't forget to mention your change in the changelog.

If you need more help, drop by at the #solidity-dev Matrix/Gitter channel.

[Midhun07]

Thank you for the detailed explanation, It is really helpful. I will start with the said option.

[Midhun07]

@cameel I have made a pull request. #11853. Please check.