Forum Magnum

Forum Magnum is the codebase powering LessWrong and the Effective Altruism Forum.

The team behind LessWrong created this codebase in 2017 as a rewrite of the original version of LessWrong, which was a difficult-to-maintain fork of reddit.

Technologies

Forum Magnum is built on top of a number of major open-source libraries.

1. Vulcan is a framework for designing social applications like forums and news aggregators. We started out using it as a library in the usual way, then forked its codebase and diverged considerably. Read their docs to understand where we've come from, but be wary of outdated information. This page is still particularly useful. CEA: see notion for more.

2. Typescript is the programming language we're using. It's like Javascript, but with type annotations. We're gradually moving from un-annotated Javascript towards having annotations on everything, and any new code should have type annotations when it's added.

3. React is a user interface programming library developed by Facebook that lets us define interface elements declaratively in the form of components. We use it to define how to render and manage state for all parts of the site.

4. GraphQL is a query language that the browser uses to get data from our servers. Most usage of GraphQL is hidden behind utility functions, but occasionally we use it directly to define APIs for accessing and mutating our data.

5. Apollo is a client-side ORM which we use for managing data on the client. We interact with it primarily via the React hooks API.

6. CkEditor5 is the default text editor for posts, comments, and some other form fields. Draft is an alternative rich text editor, which is no longer the default but which we still support.

Running locally

Requirements

• MacOS or Linux
  • Known to work on MacOS 10.15 and Ubuntu 18.04, should work on others
  • It is also known to work on Ubuntu 18.04 using Windows Subsystem for Linux
• Node
  • see .nvmrc for the required node version
  • You can use Node Version Manager to install the appropriate version of Node
  • Starting from a fresh MacOS system, try: brew install nvm to install nvm, then nvm install in the ForumMagnum directory
• Curl is optional, but needed to run some scripts and tests

Installation

Clone our repo:

git clone https://github.com/ForumMagnum/ForumMagnum.git

Install dependencies:

cd ForumMagnum
yarn install

If you want to run a local database

CEA Devs, see the ForumCredentials repository for access to a remote dev database. Otherwise, do the following:

Run a local postgres instance, version 15. For example, if you're on macos:

brew install postgresql@15
brew services start postgresql@15

createdb forummagnum

(DB name is an arbitrary choice.)

You must also have the pgvector Postgres extension installed.

Configure the schema:

psql forummagnum -f ./schema/accepted_schema.sql

TODOs:

• You won't have any database settings yet. TODO: add instructions.
  • Then run yarn ea-load-dev-db <settings file> to load the database settings from the file. (TODO: example of the file)

Creating branch-specific development databases

When developing features that require changing database schemas, it can be desirable to do this work without changing schemas in shared database instances that other developers are working on. To solve this problem, we have a script that can be used to create temporary clones of the dev database. The following commands are supported:

• yarn branchdb create clones a new dev database for the current git branch
• yarn branchdb drop drops the cloned database for the current git branch
• yarn branchdb clean drops all cloned dev databases created by this git clone
• yarn branchdb list lists all cloned dev databases created by this git clone

Start the development server

Your postgres URL for the locally-running database will be postgres://localhost/forummagnum.

yarn start-local-db --postgresUrl $YOUR_LOCAL_POSTGRES_URL

Next, select which website you are working on. If you're making a new site, open packages/lesswrong/lib/instanceSettings.ts, find the line that says

export const allForumTypes = ...

and add your forum type to the end. Then regardless of whether you're making a new site or editing an existing one, open settings-dev.json and change the line that says "forumType": "LessWrong" to the correct forum.

Or, if (and only if!) you have access to CEA's ForumCredentials repository, use

yarn ea-start

You should now have a local version running at http://localhost:3000.

It will start out with an empty database. (This means that some of the hardcoded links on the frontpage will not work). You can create users via the normal sign up process (entering a fake email is fine). The first user you’ll create will be an admin, so you’ll probably want to create at least two users to check how the site looks for non-admins. [Note for CEA: this doesn't apply to you, your database is shared with other developers.]

Documentation

Read the Docs

Some relevant pieces of documentation that will help you understand aspects of the design:

1. React hooks: intro and reference
2. JSS styles: intro
3. GraphQL: tutorial
4. Apollo: introduction and hooks API reference
5. Lodash: reference

You can also see auto-generated documentation of our GraphQL API endpoints and try out queries using GraphiQL on our server or on a development server.

Caching in CloudFront (CDN)

You can set up CloudFront to cache pages for logged out users. See this README for detailed instruction.

Understanding the codebase

Eventually, it’ll be helpful to have a good understanding of each of those technologies (both to develop new features and fix many kinds of bugs). But for now, the most useful things to know are:

• Collections – Mongo databases are organized around collections of documents. For example, the Users collection is where the user objects live. Mongo databases do not technically have a rigid schema, but VulcanJS has a pattern for files that determine the intended schema (which is used by the API, forms and permissions systems to determine what database modifications are allowed). Each collection is a subdirectory in packages/lesswrong/lib/collections.

• Components – Our React components are organized in a folder structure based loosely on our collections. (i.e. components related to the User collection go in the packages/lesswrong/components/users folder). Each component is (usually) defined in a separate .tsx file in packages/lesswrong/components and imported from packages/lesswrong/lib/components.ts.

  Some edge cases just go in a randomly picked folder (such as the RecentDiscussion components, which involve both comments and posts, but live in the comments folder)

  There are multiple ways of creating a ReactJS component. New components should be functional components, using hooks and ideally minimizing usage of higher-order components. Ideally, each component does one (relatively) simple thing and does it well, with smart components and dumb components separated out. In practice, we haven’t done a great job with this. (Scope creep turns what were once simple components into increasingly complex monstrosities that we should really refactor but haven’t gotten around to it).

  We use Vulcan’s registerComponent function to add them as children to a central “Components” table.

• Smart Forms - Vulcan also allows us to automatically generate simple forms to create and edit Documents (in the Mongo sense of the word Document, any instance of a Collection). This functionality is called Smart Forms.

  You can create an EditFoo page, which renders WrappedSmartForm, which then automagically creates a form for you. We use this to edit just about every Document in the codebase. How does it know what type of input you want though? This is the interesting part. You define the way you want to edit fields in the collection schema. So in Posts you have (selected examples):

  • Sticky
    • Because it's admin-only, it doesn't show up unless it's edited by an admin.
    • It's control is 'checkbox', which makes it editable by a simple checkbox.
    • It's grouped among admin options, so it appears with the other admin options

Development Tips

When developing, we make good use of project-wide search. One benefit of a monorepo codebase at a non-megacorp is that we can get good results just by searching for hiddenRelatedQuestion to find exactly how that database field is used.

Environment variables

• SLOW_QUERY_REPORT_CUTOFF_MS: You might want to set this to something other than the default (2000 ms), it can give a lot of false positives when you are running against a remote database.
• FM_WATCH: Set this to true or false to override the --watch CLI flag for the build process. It can sometimes be annoying for the project to rebuild on every save.

Debugging

• Use google chrome. Its debugging tools are superior.
• Use 'debugger' in code. Then Ctrl+Shift+J on your open page, and you can interactively step through the breakpoint. You can also interact with variables in scope at each step using the console at the bottom.
• Use console.warn(variable) when you want to see the stacktrace of variable
• Add the react dev tools extension to chrome, and switch to the "React" tab after pressing Ctrl+Shift+J. You can see the react component tree. Once you click on a component in the tree, you will have access to it in the console as the variable $r. For example, you can check the props or state using $r.props or $r.state.
• If you think a previous commit broke your feature, use git's builtin debugging tools
• (Note: currently aspirational): If you fix a bug, write a test for it.
• If you're trying to debug an email problem, you might want to know about forcePendingEvents.

Database Migrations

All migrations should be designed to be idempotent and should represent a one-off operation (such as updating a table schema). Operations that need to be run multiple times should instead be implemented as a server script.

After making any change that alters the database schema (eg; adding tables, adding fields, adding indexes, adding postgres functions, etc.) you must run yarn generate to update the current SQL schema and Typescript types, and commit the results to the Git repo.

• Run pending migrations with yarn migrate up [dev|staging|prod]
• Revert migrations with yarn migrate down [dev|staging|prod], but note that we treat down migrations as optionally so this may or may not work as expected
• Create a new migration with yarn migrate create my_new_migration
• View pending migrations with yarn migrate pending [dev|staging|prod]
• View executed migrations with yarn migrate executed [dev|staging|prod]

Instead of using [dev|staging|prod] above, you can also manually pass in a postgres connection string through a PG_URL environment variable. Use that option if you are not using the [EA] ForumCredentials repo or the LessWrong credentials repo.

Testing

We use Jest for unit and integration testing, and Playwright for end-to-end testing.

Jest

• Run the unit test suite with yarn unit
• Run the integration test suite with yarn integration (you may need to run yarn create-integration-db first so that the db is up-to-date)

Both commands support a -watch suffix to watch the file system, and a -coverage suffix to generate a code coverage report. After generating both code coverage reports they can be combined into a single report with yarn combine-coverage.

Playwright

There is some one-time setup before you can run the playwright tests:

• Install docker (brew install --cask docker on OSX) and start the daemon
• Download the Postgres docker image with yarn playwright-db (you can Ctrl+C to exit the container once it has successfully downloaded and started)
• Install the browsers with yarn playwright install

You can then run the tests with yarn playwright test - you can run specific tests with the -g flag.

You can also open the Playwright UI with yarn playwright test --ui, but note that unlike in CLI mode this won't automatically start the database and server so you'll also need to run yarn playwright-db and yarn start-playwright in 2 separate terminals.

For information on how to create Playwright tests see their documentation and the existing tests in the playwright directory.

The server can be accessed at localhost:3456 for debugging.

You can open the tests in a normal browser (for instance, to access the DOM inspector or debugger) with PWDEBUG=console yarn playwright test. It's strongly recommended to use the -g to only run a single test, as each test will open in a separate browser window.

Warning: The current playwright implementation is new and there are still some teething problems with starting the server correctly. If the tests routinely fail to start, remove the webservers section from playwright.config.ts and instead run yarn playwright-db and yarn start-playwright in separate terminals while running the tests.

Where to branch off of

Branch off of master and submit to master. Deploys occur when master is merged into ea-deploy and lw-deploy.

EA Forum-Specific

[CEA-Specific] Local Dev Database

The local development database is actually hosted in the cloud like staging and production. There's no reason to host your own database. It's also shared with other developers, which means if someone adds a feature which requires manual database work, there's no need for you to also do that manual work.

The test user admin credentials are in 1password. You're also welcome to create your own admin user.