dorgan

dorgan

Someone in the Elixir’s Discord guild needed a parser for yarn lock files, and I wanted to try and learn parser combinators, so I wrote a yarn lock files parser

hex.pm
Documentation
GitHub repo

Example usage:

iex> input = 
  """
  # Some comment
  # yarn lockfile v1
  key1, key2:
    val1 true
    subkey1:
      val2 123
  """

iex> {:ok, parsed} = YarnParser.decode(input)
iex> parsed
{:ok,
  %{
    "comments" => ["# Some comment", "# yarn lockfile v1"],
    "key1" => %{
      "val1" => true,
      "subkey1" => %{
        "val2" => 123
      }
    },
    "key2" => %{
      "val1" => true,
      "subkey1" => %{
        "val2" => 123
      }
    }
  }
}

iex> YarnParser.get_version(parsed)
1

It currently doesn’t handle merge conflicts like the original parser and I need to improve error messages(mostly regarding invalid indentation).

Showing Posts 1 to 6

dorgan

dorgan OP

I published version 0.3.0, it renames YarnParser.parse to YarnParser.decode and adds encoding functionality:

%{
  "prop1" => "val1",
  "block1" => %{
    "prop2" => true
  },
  "prop3" => 123
} |> YarnParser.encode()
# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
# yarn lockfile v1

block1:
  prop2 true

prop1 val1
prop3 123
ryanzidago

ryanzidago

What are te use cases for parsing lockfiles in general?

dorgan

dorgan OP

I did not ask what they needed it for, but from what I’ve read, some people parse them to gather dependencies from multiple projects or languages, but I don’t know what is done then.
Things like dependabot come to mind.

axelson

axelson

Scenic Core Team

It could also be used to generate a bill of materials like the one used in SBoM - Mix task to generate a Software Bill-of-Materials (SBoM)

kitplummer

kitplummer

I’m pretty sure I know who it was that was looking to parse a yarn.lock file. :smiley: I’ve been building some tooling to support analysis of dependencies in different language ecosystems as part of a research project. I asked a student to look into it - as both an exercise in understanding the “lock” model, as well as digging into parsers and behaviours in Elixir. We’ve been using the YarnParser, which works great.

dorgan

dorgan OP

Version 0.4.0 was published

It turns out Yarn 2 now uses YAML instead of their own format, so now YarnParser uses YamlElixir to parse newer lockfiles. Version detection is automatic.

There was also a change in the API, the decode function returns a YarnLock struct that holds lockfile metadata and dependencies. It should be easier to get the lockfile’s version and other stuff now.

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