Rewrites Mix.install dependency declarations for local testing.

This is the core feature of LivebookTest and the third stage in the pipeline:

Discovery → Exporter → **DependencyPatcher** → Runner → Report

Why dependency patching matters

Livebook notebooks are standalone documents. They declare their dependencies using Mix.install/2 with Hex version specifiers:

Mix.install([
  {:my_lib, "~> 0.5"}
])

When testing notebooks as part of a project's CI pipeline, you want those notebooks to use the current checkout of my_lib, not the published Hex version. This module rewrites the dependency declarations to use local paths instead.

Modes

• Remote (:remote) - leave the script untouched
• Local (:local) - rewrite Hex deps and existing path: deps to stable absolute paths from local_deps

How patching works

The patcher operates on the exported Elixir script (not the .livemd), using regex-based replacement to rewrite Mix.install calls:

# Hex dep - before (remote)
Mix.install([{:my_lib, "~> 0.5"}])

# Hex dep - after (local)
Mix.install([{:my_lib, path: "/abs/path/to/project"}])

# Path dep - before
Mix.install([{:my_lib, path: Path.join(__DIR__, "..")}])

# Path dep - after (local, when my_lib is in local_deps)
Mix.install([{:my_lib, path: "/abs/path/to/project"}])