Version: v4.22

Docs Readme Markdown File Auto-Generation

Stencil is able to auto-generate readme.md files for your components. This can help you to maintain consistently formatted documentation for your components which lives right next to them and renders in GitHub.

Setup

To generate markdown files, it is recommended to add the docs-readme output target to your Stencil configuration file:

stencil.config.ts
import { Config } from '@stencil/core';

export const config: Config = {
  outputTargets: [
    { 
      type: 'docs-readme'
    }
  ]
};

Generating README Files

Using the Build Command

If your project has a docs-readme output target configured in your Stencil configuration file, the Stencil build command is all that's needed to generate README docs:

npx stencil build

If you're running the build command with the --watch flag, your project's README files will automatically update without requiring multiple explicit build commands:

npm stencil build --watch

info

When running the build command with the --dev flag, README files will not be generated. This is to prevent unnecessary I/O operations during the development cycle.

If you choose not to include a docs-readme output target in your Stencil configuration file, use the --docs CLI flag as a part of the build command:

npx stencil build --docs

This will cause the Stencil compiler to perform a one-time build of your entire project, including README files.

Using the Docs Command

As an alternative to the build command, the docs command can be used to perform a one time generation of the documentation:

npx stencil docs

Running stencil docs will generate documentation for all documentation output targets, not just docs-readme.

README Sections

Most generated markdown content will automatically be generated without requiring any additional configuration. Content is generated based on its Stencil component, rather than requiring you to configure multiple flags. Each section below describes the different types of content Stencil recognizes and will automatically generate.

Custom Markdown Content

Once you've generated a readme.md file, you can add your own markdown content to the file. You may add any content above the following comment in a component's readme.md:

Custom content goes here!
<!-- Auto Generated Below -->

Any custom content placed above this comment will be persisted on subsequent builds of the README file.

Internal Components

A Stencil component may be marked as internal to a library using the unofficial JSDoc @internal tag. By placing @internal in a component's class-level JSDoc it will skip the generation of the README for the component.

In the code block below, @internal is added to the JSDoc for MyComponent:

A component with @internal in its JSDoc
/**
 * @internal
 */
@Component({
  tag: 'my-component',
  shadow: true,
})
export class MyComponent { /* omitted */ }

The usage of @internal causes no README to be generated for MyComponent.

If a README already exists for the component, it will not be updated.

Deprecation Notices

A Stencil component may be marked as deprecated using the JSDoc @deprecated tag. By placing @deprecated in a component's class-level JSDoc it will cause the generated README to denote the component as deprecated.

For a component with the JSDoc:

A component with @deprecated in its JSDoc
/**
 * @deprecated since v2.0.0
 */
@Component({
  tag: 'my-component',
  shadow: true,
})
export class MyComponent { /* omitted */ }

In the code block above, @deprecated is added to the JSDoc for MyComponent. This causes the generated README to contain:

> **[DEPRECATED]** since v2.0.0

The deprecation notice will always begin with > **[DEPRECATED]**, followed by the description provided in the JSDoc. In this case, that description is "since v2.0.0".

The deprecation notice will be placed after the custom content in the README.

If a component is not marked as deprecated, this section will be omitted from the generated README.

Component Overview

A Stencil component that has a JSDoc comment on its class component like so:

A component with an overview in its JSDoc
/**
 * A simple component for formatting names
 *
 * This component will do some neat things!
 */
@Component({
  tag: 'my-component',
  shadow: true,
})
export class MyComponent { }

will generate the following section in your component's README:

## Overview

A simple component for formatting names

This component will do some neat things!

The overview will be placed after the deprecation notice section of the README.

If a component's JSDoc does not contain an overview, this section will be omitted from the generated README.

Usage Examples

Usage examples are user-generated markdown files that demonstrate how another developer might use a component. These files are separate from a component's README file, and are placed in a usage/ directory adjacent to a component's implementation.

The content of these files will be added to a Usage section of the generated README. This allows you to keep examples right next to the code, making it easy to include them in a documentation site or other downstream consumer(s) of your docs.

The example usage file below describes how to use a component defined in src/components/my-component/my-component.tsx:

src/components/my-component/usage/my-component-usage.md
# How to Use `my-component`

This component is used to provide a way to greet a user using their first, middle, and last name.
This component will properly format the provided name, even when all fields aren't provided:

```html
<my-component first="Stencil"></my-component>
<my-component first="Stencil" last="JS"></my-component>
```

When the README for my-component is regenerated, following will be added to the README:

## Usage

### My-component-usage

# How to Use `my-component`

This component is used to provide a way to greet a user using their first, middle, and last name.
This component will properly format the provided name, even when all fields aren't provided:

```html
<my-component first="Stencil"></my-component>
<my-component first="Stencil" last="JS"></my-component>
```

caution

Stencil does not check that your usage examples are up-to-date. If you make any changes to your component's API, you'll need to update your usage examples manually.

The usage section will be placed after the overview section of the README.

If a component's directory does not contain any usage files, this section will be omitted from the generated README.

@Prop() Details

Usages of Stencil's @Prop() decorator are described in a table containing the following information for each usage of @Prop():

Property: The name of the property on the TypeScript class.
Attribute: The name of the attribute associated with the property name.
Description: A description of the property, if one was given in a JSDoc comment for the property.
Type: The TypeScript type of the property.
Default: The default value of the property.

For the following usages of @Prop() in a component:

export class MyComponent {
  /**
   * The first name
   */
  @Prop() first!: string; // the '!' denotes a required property
  /**
   * @deprecated since v2.1.0
   */
  @Prop() middle: string;
  @Prop() lastName = "Smith";

  // ...
}

The following section will be generated:

## Properties

| Property             | Attribute   | Description                                                            | Type     | Default     |
| -------------------- | ----------- | ---------------------------------------------------------------------- | -------- | ----------- |
| `first` _(required)_ | `first`     | The first name                                                         | `string` | `undefined` |
| `lastName`           | `last-name` |                                                                        | `string` | `"Smith"`   |
| `middle`             | `middle`    | <span style="color:red">**[DEPRECATED]**</span> since v2.1.0<br/><br/> | `string` | `undefined` |

The properties section will be placed after the usage examples section of the README.

If a component does not use the @Prop() decorator, this section will be omitted from the generated README.

@Event() Details

Usages of Stencil's @Event() decorator are described in a table containing the following information for each usage of @Event():

Event: The name of the property on the TypeScript class decorated with @Event().
Description: A description of the property, if one was given in a JSDoc comment for the property.
Type: The TypeScript type of the property.

For the following usages of @Event() in a component:

export class MyComponent {
  /**
   * Emitted when an event is completed
   */
  @Event() todoCompleted: EventEmitter<number>;
  /**
   * @deprecated
   */
  @Event() todoUndo: EventEmitter<number>;

  // ...
}

The following section will be generated:

## Events

| Event           | Description                                                | Type                  |
| --------------- | ---------------------------------------------------------- | --------------------- |
| `todoCompleted` | Emitted when an event is completed                         | `CustomEvent<number>` |
| `todoUndo`      | <span style="color:red">**[DEPRECATED]**</span> <br/><br/> | `CustomEvent<number>` |

The events section will be placed after the @Prop() section of the README.

If a component does not use the @Event() decorator, this section will be omitted from the generated README.

@Method() Details

Components that use Stencil's @Method() decorator will have a section describing each usage @Method.

Each usage of @Method will be documented with its own subsection containing the following:

The method signature will be used as the heading for each subsection
A description of the method will immediately follow, if one was provided in a JSDoc
A 'Parameters' section that contains a table the describes the name, TypeScript type, and description of each parameter of the method
A 'Returns' section that contains the return type of the method, along with a description of the returned value.

For the following usages of @Method() in a component:

export class MyComponent {
  /**
   * Scroll by a specified X/Y distance in the component.
   *
   * @param x The amount to scroll by on the horizontal axis.
   * @param y The amount to scroll by on the vertical axis.
   * @param duration The amount of time to take scrolling by that amount.
   * @returns the total distance travelled
   */
  @Method()
  async scrollByPoint(x: number, y: number, duration: number): Promise<number> { /* omitted */ }

  // ...
}

The following section will be generated:

## Methods

### `scrollByPoint(x: number, y: number, duration: number) => Promise<number>`

Scroll by a specified X/Y distance in the component.

#### Parameters

| Name       | Type     | Description                                          |
| ---------- | -------- | ---------------------------------------------------- |
| `x`        | `number` | The amount to scroll by on the horizontal axis.      |
| `y`        | `number` | The amount to scroll by on the vertical axis.        |
| `duration` | `number` | The amount of time to take scrolling by that amount. |

#### Returns

Type: `Promise<number>`

the total distance travelled

The methods section will be placed after the @Event section of the README.

If a component does not use the @Method() decorator, this section will be omitted from the generated README.

@slot Details

A component that uses slots may describe its slots in the component's JSDoc using the Stencil-specific @slot JSDoc tag. The @slot tag follows the following format:

@slot [slot-name] - [description]

where slot-name corresponds to the name of the slot in the markup, and description describes the usage of the slot.

For this JSDoc tag to be read properly, the following is required:

Either slot-name or description must be included. Both may be included though.
The '-' separating the two is required.

For the default slot, omit the slot-name.

This information is presented in a table containing the following columns:

Slot: The name of the slot. The default slot will have no name/be empty.
Description: A description of the slot, if one was given.

For the following usages of @slot() in a component:

/**
 * @slot - Content is placed between the named slots if provided without a slot.
 * @slot primary - Content is placed to the left of the main slotted-in text.
 * @slot secondary - Content is placed to the right of the main slotted-in text.
 */
@Component({
  tag: 'my-component',
  shadow: true,
})
export class MyComponent {
  // ...
  
  render() {
    return (
      <section>
        <slot name="primary"></slot>
        <div class="content">
          <slot></slot>
        </div>
        <slot name="secondary"></slot>
      </section>
    );
  }
}

The following table is generated:

## Slots

| Slot          | Description                                                           |
| ------------- | --------------------------------------------------------------------- |
|               | Content is placed between the named slots if provided without a slot. |
| `"primary"`   | Content is placed to the left of the main slotted-in text.            |
| `"secondary"` | Content is placed to the right of the main slotted-in text.           |

The slots section will be placed after the @Method section of the README.

If a component's top-level JSDoc does not use @slot tags, this section will be omitted from the generated README.

Shadow Parts

A component that uses CSS shadow parts may describe the component's shadow parts in the component's JSDoc using the Stencil-specific @part JSDoc tag. The @part tag follows the following format:

@part [part-name] - [description]

where part-name corresponds to the name of the shadow part in the markup, and description describes its usage.

For this tag to be read properly, the following is required:

Either part-name or description must be included, although using both is strongly encouraged.
The '-' separating the two is required.

This information is presented in a table containing the following columns:

Part: The name of the shadow part.
Description: A description of the shadow part, if one was given.

For the following usages of @part() in a component:

/**
 * @part label - The label text describing the component.
 */
@Component({
  tag: 'my-component',
  styleUrl: 'my-component.css',
  shadow: true,
})
export class MyComponent {
  // ...

  render() {
    return (
      <div part="label">
        <slot></slot>
      </div>
    );
  }
}

The following table will be generated:

## Shadow Parts

| Part                                                        | Description                              |
| ----------------------------------------------------------- | ---------------------------------------- |
| `"label"`                                                   | The label text describing the component. |

The shadow parts section will be placed after the @Slot Details of the README.

If a component's top-level JSDoc does not use @part tags, this section will be omitted from the generated README.

Styling Details

Styling in CSS files can be documented in Stencil components as well. One use case for documenting styles using Stencil is to note a CSS variable that a component's styling depends on. Using the @prop JSDoc in a component's CSS file, Stencil can generate this documentation as well.

This information is presented in a table containing the following columns:

Name: The name of the custom property.
Description: A description of the custom property, if one was given.

For the following usages of @prop in a component's css file:

:host {
  /**
   * @prop --border-radius: Border radius of the avatar and inner image
   */
  border-radius: var(--border-radius);
}

The following table will be generated:

## CSS Custom Properties

| Name              | Description                                 |
| ----------------- | ------------------------------------------- |
| `--border-radius` | Border radius of the avatar and inner image |

The styling details section will be placed after the Shadow Parts Details of the README.

If a component's styles does not include styling details, this section will be omitted from the generated README.

Custom Footers

Removing or customizing the footer can be done by adding a footer property to the output target. This string is added to the generated Markdown files without modification, so you can use Markdown syntax in it for rich formatting:

stencil.config.ts
import { Config } from '@stencil/core';

export const config: Config = {
  outputTargets: [
    {
      type: 'docs-readme',
      footer: '*Built with love!*',
    }
  ]
};

The following footer will be placed at the bottom of your component's README file:

*Built with love!*

Configuration

Specifying the Output Directory

By default, a README file will be generated in the same directory as the component it corresponds to. This behavior can be changed by setting the dir property on the output target configuration. Specifying a directory will create the structure {dir}/{component}/readme.md.

stencil.config.ts
import { Config } from '@stencil/core';

export const config: Config = {
  outputTargets: [
    {
      type: 'docs-readme',
      dir: 'output'
    }
  ]
};

Strict Mode

Adding strict: true to the output target configuration will cause Stencil to output a warning whenever the project is built with missing documentation.

stencil.config.ts
import { Config } from '@stencil/core';

export const config: Config = {
  outputTargets: [
    {
      type: 'docs-readme',
      strict: true
    }
  ]
};

When strict mode is enabled, the following items are checked:

@Prop() usages must be documented, unless the property is marked as @deprecated
@Method() usages must be documented, unless the method is marked as @deprecated
@Event() usages must be documented, unless the event is marked as @deprecated
CSS Part usages must be documented

Setup​

Generating README Files​

Using the Build Command​

Using the Docs Command​

README Sections​

Custom Markdown Content​

Internal Components​

Deprecation Notices​

Component Overview​

Usage Examples​

@Prop() Details​

@Event() Details​

@Method() Details​

@slot Details​

Shadow Parts​

Styling Details​

Custom Footers​

Configuration​

Specifying the Output Directory​

Strict Mode​

Contents

Setup

Generating README Files

Using the Build Command

Using the Docs Command

README Sections

Custom Markdown Content

Internal Components

Deprecation Notices

Component Overview

Usage Examples

@Prop() Details

@Event() Details

@Method() Details

@slot Details

Shadow Parts

Styling Details

Custom Footers

Configuration

Specifying the Output Directory

Strict Mode