Elixir mix lockfiles fail to parse certain git definitions

[tophersmith]

Describe the bug
semgrep's semdep elixir/mix parser has a bug where :git definitions fail when they do not use the :tag checkout option.

See: https://hexdocs.pm/mix/1.14.5/Mix.Tasks.Deps.html#module-git-options-git

This causes a None in the parsed_lockfile list in mix.py here:

semgrep/cli/src/semdep/parsers/mix.py

Line 210 in 8bbbdfe

parsed_lockfile, parsed_manifest, errors = safe_parse_lockfile_and_manifest(

and causes an unpacking error in the following for loop on

semgrep/cli/src/semdep/parsers/mix.py

Line 192 in 8bbbdfe

for line_number, (package, version) in lockfile_deps:

I believe that the problem/solution is in the mix parser definition here:

semgrep/cli/src/semdep/parsers/mix.py

Line 106 in 8bbbdfe

>> string("tag")

where you'll need to support ref and branch

To Reproduce
scan a mix.lock file with a definition like:
"mylib": {:git, "https://github.com/my_org/mylib.git", "1962a9d9a06fe559814724101e05e0a14e55beeb", [ref: "1962a9d9a06fe559814724101e05e0a14e55beeb"]},

Expected behavior
parse the lockfile completely and try to catch errors like this for mis-parsed files as well

Screenshots
N/A

What is the priority of the bug to you?
P1: important to fix or quite annoying

Environment
This is in all builds

Use case
I can parse elixir dependencies

[tophersmith]

A few related parser issues I'm finding as well:

lockfile can have these definitions for dependencies that aren't supported by this parser:
{:hex, :testing, "1.0.1", "1234bb4db5b32fc0f8aa5c4a2040348b4aa36687100fb8837b850e90cf60e06", [:mix], [], "hexpm"}
(i.e. there's no final comma, quoted_str)

semgrep/cli/src/semdep/parsers/mix.py

Line 87 in 8bbbdfe

<< comma

Also, git tag/refs can be empty:
{:git, "https://github.com/okeuday/erlang_term.git", "9eb28c6eb54acab3d491fa69655f9eaf663378da", []},

semgrep/cli/src/semdep/parsers/mix.py

Line 106 in 8bbbdfe

>> string("tag")

FWIW, I am also getting frequent issues related to trailing newlines in .exs files and I don't understand why.
Failed to parse [bold]discord_voice_curator/deps/observer_cli/mix.exs[/bold] at [bold]17:1[/bold] - expected 'did not
find other parser'
17 |
for this file: https://github.com/zhongwencool/observer_cli/blob/master/mix.exs

[jarrydlee]

Hey @tophersmith, I'm looking at these issues now. I'll link a PR once it's up.