Do not whitelist remapping targets

[cameel]

Originally requested in #11688 (comment).

Abstract

Normally, importing files from arbitrary directories requires whitelisting those directories using --allow-paths. That's not the case when the import contains a remapping. This automatic whitelisting should be removed.

Example

This causes an error:

mkdir /tmp/{dir,anotherdir}
touch /tmp/anotherdir/contract.sol
cd /tmp/dir/
echo "import '/tmp/anotherdir/contract.sol';" | solc -

Error: Source "/tmp/anotherdir/contract.sol" not found: File outside of allowed directories.
 --> <stdin>:1:1:
  |
1 | import '/tmp/anotherdir/contract.sol';
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

While this does not:

echo "import '/tmp/dir/contract.sol';" | solc - /tmp/dir/=/tmp/anotherdir/

This is especially weird when the remapping does not really do anything:

echo "import '/tmp/anotherdir/contract.sol';" | solc - /tmp/anotherdir/=/tmp/anotherdir/

Specification

Remapping prefixes, targets and contexts should not be added to allowed paths.

Backwards Compatibility

The change is not backwards-compatible. Users relying on this behavior will have to start adding --allowed-paths to their commands.

[soroosh-sdi]

I like to try this issue, if it's not urgent

[soroosh-sdi]

I think we also need a new test case; I don't know you add tests for this kind of issues or not. a downside comes to my mind is that adding tests for such small issues could make running our tests so time consuming after couple of years.
EDIT: we have lots of tests in CommandLineParser.cpp which tests this feature implicitly.

[cameel]

It's not urgent but this is not the best moment to start working on this because #11688 and #12007 have not been merged yet and they change a lot regarding --allow-paths. In particular #11688 adds a complete suite of tests so testing this should no longer be a problem.

It's also a breaking change so it should be based on breaking rather than develop branch and will only be released in 0.9.0, some time in the future.

[cameel]

@soroosh-sdi If you're looking for a task, how about one of these?:

• [CLI] Unqualified library name in --libraries option matches any qualified link reference with the same library name #10298
• Make the hard-coded parts of the optimiser sequence configurable #9627
• [CLI] Rewrite solc --link to use LinkerObject #10308
• Clean up the helpers around errors #11959
• [soltest] Directive for skipping SMTChecker tests on specific platforms #11870
• Pretty print expected json output of command line tests. #7665

[soroosh-sdi]

please move this issue to Done, after merging #12021.

[cameel]

Sure. Move to "review in progress" now. It will get moved to "done" automatically when the issue is closed.

Merging needs to wait for #12150 unfortunately.