good-fences-rs-core

A rust reimplementation of good-fences:

Good-fences is a tool that allows you to segment a TypeScript project into conceptual areas and manage dependencies between those areas. This is mostly a concern for large projects with many people working on them, where it is impossible for every developer to have a wholistic understanding of the entire codebase. JavaScript's module system is a specialized form of anarchy because any file can import any other file, possibly allowing access to code that was really meant to be an internal implementation detail of some larger system. Other languages have concepts like DLL boundaries and the internal keyword to mitigate this. Good-fences provides a way to enforce similar boundaries in the TypeScript world.

Motivation

The original good-fences implementation came with some limitations:

• Its native dependencies only supported Node.js < v15.
• It had performance issues in some of our biggest projects (scanning 40k+ files).

Rust's safe concurrency and memory safety allows us to re-write original project with additional performance benefits, leaning on swc for javascript/typescript parsing.

Getting Started

good-fences-rs includes a CLI and an API, under the name @good-fences/api.

Requirements

Compatible with x86 and x64 windows and linux platforms.

Linux:

• GCLIB >= 2.27 (preinstalled with ubuntu 18)
• Node.js > 14
• npm

Installing CLI

Via npm.

npm install -g @good-fences/api

Cloning the repo:

git clone https://github.com/Adjective-Object/good-fences-rs-core
cd good-fences-rs-core
yarn
yarn run build

Installing as Node dependency

npm install @good-fences/api

Use it in your project:

import { goodFences } from '@good-fences/api';

goodFences({...});

Using the CLI

To run the good-fences cli we need at least two things:

• fence.json configuration files.
• A tsconfig.json file. (see tsconfig reference)

Let's assume a project like this:

├── my-project
│   ├── src
│   │   ├── **/*.ts
|   |   ├── index.js
|   │   ├── fence.json
|   tsconfig.json

From your terminal you can run this:

cd my-project
good-fences src

Arguments

---

• [paths]: the cli takes only the paths argument, a list, separated with spaces, of all directories that are going to be scanned.

Options

---

--project or -p

If you have your tsconfig file splitt and want to use the one containing compilerOptions.paths instead of the default tsconfig.json

good-fences src --project tsconfig.with-paths.json

--baseUrl

In cases like the one above, it could be that different tsconfig files have different compilerOptions.baseUrl configuration, you can override that valua from your specified --project file with --baseUrl flag.

good-fences src --project tsconfig.without-baseurl.json --baseUrl .

--output or -o

The --output flag takes a path. At the end of checking, fence violation errors will be saved to the provided path as json.

good-fences src --output fenceViolations.json
cat fenceViolations.json

For some cases, scanning your cwd could be needed but most projects have node_modules that isn't necessary to perform evaluations, in those cases --ignoreExternalFences makes good-fences skip all directories and files from node_modules.

good-fences . --ignoreExternalFences

--ignoredDirs

This takes a list of regular expressions as input values, separated with spaces. In case certain directories need to be ignored during the fence evaluation, this will perform regular expression matching on fence paths to ignore them (e.g. --ignoredDirs lib will not evaluate files under any lib directory).

good-fences src --ignoredDirs ignored1 ignored2 ...

Development

Setting up the Development Environment

1. Install a container engine: The repo uses a devcontainer, which is like a lightweight virtual machine that contains a pre-configured development environment.

   It is intended to support both Docker and podman, which are two different container engines. This is kind of arbitrary, and I might choose to revert it in the future if it presents issues.

   On windows, install Docker-Desktop On linux, you can install either docker or podman (via podman-docker)

2. Set up your local config The devcontainer mounts some local directories from your machine into the container. If you do not have these already, you will have to create them, or comment out the bind mounts in the devcontainer.

   • $HOME/.ssh -- This is mounted so the container can access your SSH keys to push/pull from the git remote.
     This should already exist if you have ever configured an SSH key via ssh-keygen, which is the normal way to clone a git repo.

   Note that if you are developing in WSL, you should create these files in wsl, not within your windows filesystem.

3. Configure your local user identity From within the repo, configure your local git identity:

   ❯ git config --local user.name "Your Name Here"
   ❯ git config --local user.email "[email protected]"
   

   Note that you have to do this from within the repo's folder so it will be persisted into the devcontainer when the repo's folder is mounted as a volume. If you are in WSL, you need to do this within the repo's out folder in WSL

4. Install recommended extensions Install the recommended extensions from this repo.

   Ctrl+Shift+P > Extensions: Show Recommended Extensions, then install all recommended extensions from the left navbar that opens up.

5. Build and open in the devcontainer

   Ctrl+Shift+P > Rebuild and Reopen In Container Select the development container based on your container engine (podman or docker)

   • If installation stalls on docker inspect --type image ubuntu:24.10, you may need to feth the base image manually
   • Run docker inspect --type image ubuntu:24.10
   • If it fails with Error response from daemon: No such image: ubuntu, then run docker pull ubuntu:24.10

6. (optional) mount additional projects into the dev container To test unused-finder against your repo during development, uncomment the commented-out "mount" in the checked-in .devcontainer:

    // This mounts client-web checked out next to this repo for testing, left checked-in here for convenience.
    // Don't commit it, though!
    // "source=${localWorkspaceFolder}/../client-web,target=/workspaces/client-web,type=bind,consistency=cached",

   The provided example mounts client-web as a target repo

Flamegraphs and profiling

For profiling, you can use samply

# This isn't installed by default in the dev container because it has to be built from source,
# which takes a long time
#
# Must be built with --locked dependencies
# See: https://github.com/mstange/samply/issues/341
cargo install samply --locked

To profile a test, first build the test binary

# This will print the path of the test binary
cargo test -p unused_finder --no-run

# Then, run samply on the test binary binary
samply record target/debug/deps/unused_finder-3aa70b00191bd4df

Note: Working in WSL

The devcontainer is configured to allow perf events, but the host system must also be configured to allow perf events. On windows, devcontainers will probably be running under wsl. This means opening up wsl, and running the following:

# from within WSL
echo '1' | sudo tee /proc/sys/kernel/perf_event_paranoid

Then, close and restart your devcontainers