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 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 Read their docs to understand where we've come from, but be wary of outdated information.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 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

Installation

Prerequisites:

• Install MongoDB: https://docs.mongodb.com/manual/installation/

Clone our repo:

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

(CEA Devs, see the ForumCredentials repository for secrets)

Install dependencies:

cd ForumMagnum
yarn install

Start the development server:

mkdir myLocalDatabase
mongod --dbpath ./myLocalDatabase

yarn [start|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. Underscore: reference
6. MongoDB: manual

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.

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
  • Title
    • It's control is 'EditTitle', which means the Smart Form will look in Components for an EditTitle component, and then use that as the UI for modifying the Title.

• useFoo (React Hooks) - We make heavy use of React hooks for querying data, managing state, and accessing shared data like the current user.

• withFoo (Higher Order Components) – Higher-order components exist as alternatives for most hooks, and are sometimes used because class-components cannot use hooks. However, these are deprecated and we are migrating towards only using hooks.

• Fragments – GraphQL queries are made using fragments, which describe the fields from a given database object you want to fetch information on. There’s a common failure mode where someone forgets to update a fragment with new fields, and then the site breaks the next time a component attempts to use information from the new field.

• makeEditable - To add a long text field to a schema, use makeEditable. It add the correct control component, and creates the necessary callbacks to sync it with the Revisions table.

• Configuration and Secrets We store most configuration and secrets in the database, not in environment variables like you might expect. See packages/lesswrong/server/databaseSettings.ts for more.

• Logging - If there's a part of the codebase you often want to see debug logging for, you can create a specific debug logger for that section by using loggerConstructor(scope). You can then enable or disable that logger by setting the public database setting debuggers to include your scope, or by setting the instance setting instanceDebuggers. See packages/lesswrong/lib/utils/logging.ts for more.

• Collection callbacks - One important thing to know when diving into the codebase is how much logic is done by callbacks. Collections have hooks on them where we add callbacks that react to CRUD operations. They can fire before or after the operation. The running of these callbacks is found in packages/lesswrong/server/vulcan-lib/mutators.ts.

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.

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.

Testing

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

Cypress

• To run Cypress tests locally, first run yarn ea-start-testing-db, then in a separate terminal run either yarn ea-cypress-run for a CLI version, or yarn ea-cypress-open for a GUI version. To run specific tests in the CLI, you can use the -s <glob-file-pattern> option.
• Test database instance settings for Cypress are stored under ./settings-test.json.
• For the basics of writing Cypress tests, see Writing your first test. Primarily you'll use cy.get() to find elements via CSS selectors, cy.contains() to find elements via text contents, cy.click() and cy.type() for input, and cy.should() for assertions. Feel free to steal from existing tests in ./cypress/integration/.
• Add custom commands under ./cypress/support/commands.js, and access them via cy.commandName().
• Seed data for tests is stored under ./cypress/fixtures, and can be accessed using cy.fixture('<filepath>'). See here for more.
• To execute code in a node context, you can create a task under ./cypress/plugins/index.js. Tasks are executed using cy.task('<task-name>', args).

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 on MongoDB 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.