Frontend

Frontend

This is a guide to help the Coder community and also Coder members contribute to our UI. It is ongoing work but we hope it provides some useful information to get started. If you have any questions or need help, please send us a message on our Discord server. We'll be happy to help you.

Running the UI

You can run the UI and access the dashboard in two ways:

Build the UI pointing to an external Coder server: CODER_HOST=https://mycoder.com pnpm dev inside of the site folder. This is helpful when you are building something in the UI and already have the data on your deployed server.
Build the entire Coder server + UI locally: ./scripts/develop.sh in the root folder. It is useful when you have to contribute with features that are not deployed yet or when you have to work on both, frontend and backend.

In both cases, you can access the dashboard on http://localhost:8080. If you are running the ./scripts/develop.sh you can log in using the default credentials: [email protected] and SomeSecurePassword!.

Tech Stack

All our dependencies are described in site/package.json but here are the most important ones:

React as framework
Typescript to keep our sanity
Vite to build the project
Material V5 for UI components
react-router for routing
TanStack Query v4 for fetching data
axios as fetching lib
Playwright for end-to-end (E2E) testing
Jest for integration testing
Storybook and Chromatic for visual testing
PNPM as package manager

Structure

All the code related to the UI is inside the site folder and we defined a few conventions to help people to navigate through it.

e2e - End-to-end (E2E) tests
src - Source code
- mocks - Manual mocks used by Jest
- @types - Custom types for dependencies that don't have defined types (largely code that has no server-side equivalent)
- api - API code as function calls and types
  - queries - react-query queries and mutations
- components - UI components
- hooks - Hooks that can be used across the application
- pages - Page components
- testHelpers - Helper functions to help with integration tests
- util - Helper functions that can be used across the application
static - Static UI assets like images, fonts, icons, etc

Routing

We use react-router as our routing engine and adding a new route is very easy. If the new route needs to be authenticated, put it under the <RequireAuth> route and if it needs to live inside of the dashboard, put it under the <DashboardLayout> route.

The RequireAuth component handles all the authentication logic for the routes and the DashboardLayout wraps the route adding a navbar and passing down common dashboard data.

Pages

Pages are the top-level components of the app. The page component lives under the src/pages folder and each page should have its own folder so we can better group the views, tests, utility functions and so on. We use a structure where the page component is responsible for fetching all the data and passing it down to the view. We explain this decision a bit better in the next section.

ℹ️ Code that is only related to the page should live inside of the page folder but if at some point it is used in other pages or components, you should consider moving it to the src level in the utils, hooks or components folder.

States

A page usually has at least three states: loading, ready/success, and error, so always remember to handle these scenarios while you are coding a page. We also encourage you to add visual testing for these three states using a *.stories.ts file.

Fetching data

We use TanStack Query v4 to fetch data from the API. The queries and mutation should be placed inside of the api/queries folder when it is possible.

Where to fetch data

In the past, our approach involved creating separate components for page and view, where the page component served as a container responsible for fetching data and passing it down to the view.

For instance, when developing a page to display users, we would have a UsersPage component with a corresponding UsersPageView. The UsersPage would handle API calls, while the UsersPageView managed the presentational logic.

Over time, however, we encountered challenges with this approach, particularly in terms of excessive props drilling. To address this, we opted to fetch data in proximity to its usage. Taking the example of displaying users, in the past, if we were creating a header component for that page, we would have needed to fetch the data in the page component and pass it down through the hierarchy (UsersPage -> UsersPageView -> UsersHeader). Now, with libraries such as react-query, data fetching can be performed directly in the UsersHeader component, allowing UI elements to declare and consume their data-fetching dependencies directly, while preventing duplicate server requests (more info).

To simplify visual testing of scenarios where components are responsible for fetching data, you can easily set the queries' value using parameters.queries within the component's story.

export const WithQuota: Story = {
  parameters: {
    queries: [
      {
        key: getWorkspaceQuotaQueryKey(MockUser.username),
        data: {
          credits_consumed: 2,
          budget: 40,
        },
      },
    ],
  },
};

API

We are using axios as our fetching library and writing the API functions in the site/src/api/api.ts files. We also have auto-generated types from our Go server on site/src/api/typesGenerated.ts. Usually, every endpoint has its own Request and Response types, but sometimes you need to pass extra parameters to make the call, like in the example below:

export const getAgentListeningPorts = async (
  agentID: string,
): Promise<TypesGen.ListeningPortsResponse> => {
  const response = await axiosInstance.get(
    `/api/v2/workspaceagents/${agentID}/listening-ports`,
  );
  return response.data;
};

Sometimes, a frontend operation can have multiple API calls, so it is okay to wrap it as a single function.

export const updateWorkspaceVersion = async (
  workspace: TypesGen.Workspace,
): Promise<TypesGen.WorkspaceBuild> => {
  const template = await getTemplate(workspace.template_id);
  return startWorkspace(workspace.id, template.active_version_id);
};

If you need more granular errors or control, you may should consider keep them separated and use XState for that.

Components

The codebase is currently using MUI v5. Please see the official documentation. In general, favor building a custom component via MUI instead of plain React/HTML, as MUI's suite of components is thoroughly battle-tested and accessible right out of the box.

Structure

Each component gets its own folder. Make sure you add a test and Storybook stories for the component as well. By keeping these tidy, the codebase will remain easy to navigate, healthy and maintainable for all contributors.

Accessibility

We strive to keep our UI accessible.

In general, colors should come from the app theme, but if there is a need to add a custom color, please ensure that the foreground and background have a minimum contrast ratio of 4.5:1 to meet WCAG level AA compliance. WebAIM has a great tool for checking your colors directly, but tools like Dequeue's axe DevTools can also do automated checks in certain situations.

When using any kind of input element, always make sure that there is a label associated with that element (the label can be made invisible for aesthetic reasons, but it should always be in the HTML markup). Labels are important for screen-readers; a placeholder text value is not enough for all users.

When possible, make sure that all image/graphic elements have accompanying text that describes the image. <img /> elements should have an alt text value. In other situations, it might make sense to place invisible, descriptive text inside the component itself using MUI's visuallyHidden utility function.

import { visuallyHidden } from "@mui/utils";

<Button>
  <GearIcon />
  <Box component="span" sx={visuallyHidden}>
    Settings
  </Box>
</Button>;

Should I create a new component?

As with most things in the world, it depends. If you are creating a new component to encapsulate some UI abstraction like UsersTable it is ok but you should always try to use the base components that are provided by the library or from the codebase. It's recommended that you always do a quick search before creating a custom primitive component like dialogs, popovers, buttons, etc.

Testing

We use three types of testing in our app: End-to-end (E2E), Integration and Visual Testing.

End-to-End (E2E)

These are useful for testing complete flows like "Create a user", "Import template", etc. We use Playwright. If you only need to test if the page is being rendered correctly, you should consider using the Visual Testing approach.

ℹ️ For scenarios where you need to be authenticated, you can use test.use({ storageState: getStatePath("authState") }).

For ease of debugging, it's possible to run a Playwright test in headful mode running a Playwright server on your local machine, and executing the test inside your workspace.

You can either run scripts/remote_playwright.sh from coder/coder on your local machine, or execute the following command if you don't have the repo available:

bash <(curl -sSL https://raw.githubusercontent.com/coder/coder/main/scripts/remote_playwright.sh) [workspace]

The scripts/remote_playwright.sh script will start a Playwright server on your local machine and forward the necessary ports to your workspace. At the end of the script, you will land inside your workspace with environment variables set so you can simply execute the test (pnpm run playwright:test).

Integration

Test user interactions like "Click in a button shows a dialog", "Submit the form sends the correct data", etc. For this, we use Jest and react-testing-library. If the test involves routing checks like redirects or maybe checking the info on another page, you should probably consider using the E2E approach.

Visual testing

We use visual tests to test components without user interaction like testing if a page/component is rendered correctly depending on some parameters, if a button is showing a spinner, if loading props are passed correctly, etc. This should always be your first option since it is way easier to maintain. For this, we use Storybook and Chromatic.

ℹ️ To learn more about testing components that fetch API data, refer to the Where to fetch data section.

What should I test?

Choosing what to test is not always easy since there are a lot of flows and a lot of things can happen but these are a few indicators that can help you with that:

Things that can block the user
Reported bugs
Regression issues

Tests getting too slow

A few times you can notice tests can take a very long time to get done. Sometimes it is because the test itself is complex and runs a lot of stuff, and sometimes it is because of how we are querying things. In the next section, we are going to talk more about them.

Using `ByRole` queries

One thing we figured out that was slowing down our tests was the use of ByRole queries because of how it calculates the role attribute for every element on the screen. You can read more about it on the links below:

Even with ByRole having performance issues we still want to use it but for that, we have to scope the "querying" area by using the within command. So instead of using screen.getByRole("button") directly we could do within(form).getByRole("button").

❌ Not ideal. If the screen has a hundred or thousand elements it can be VERY slow.

user.click(screen.getByRole("button"));

✅ Better. We can limit the number of elements we are querying.

const form = screen.getByTestId("form");
user.click(within(form).getByRole("button"));

`jest.spyOn` with the API is not working

For some unknown reason, we figured out the jest.spyOn is not able to mock the API function when they are passed directly into the services XState machine configuration.

❌ Does not work

import { getUpdateCheck } from "api/api"

createMachine({ ... }, {
  services: {
    getUpdateCheck,
  },
})

✅ It works

import { getUpdateCheck } from "api/api"

createMachine({ ... }, {
  services: {
    getUpdateCheck: () => getUpdateCheck(),
  },
})

See an opportunity to improve our docs? Make an edit.

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Running the UI

Tech Stack

Structure

Routing

Pages

States

Fetching data

Where to fetch data

API

Components

Structure

Accessibility

Should I create a new component?

Testing

End-to-End (E2E)

Integration

Visual testing

What should I test?

Tests getting too slow

Using ByRole queries

jest.spyOn with the API is not working

Using `ByRole` queries

`jest.spyOn` with the API is not working