shiki-twoslash

shiki-twoslash

Sets up markdown code blocks to run through shiki which means it gets the VS Code quality syntax highlighting. This part is basically the same as gatsby-remark-shiki.

Why Shiki? Shiki uses the same syntax highlighter engine as VS Code, which means no matter how complex your code is - it will syntax highlight correctly.

In addition to all the languages shiki handles (it's a lot), this module adds opt-in @typescript/twoslash rendering for TypeScript code blocks.

This module powers the code samples on the TypeScript website.

With a bit of work you can explain complicated code in a way that lets people introspect at their own pace.

Plugin Setup

Express Setup

Read this PR and apply the same to your project.

Setup

1. Install the dependency: yarn add shiki-twoslash

2. Include "shiki-twoslash" in the plugins section of gatsby-transformer-remark

   {
     resolve: `gatsby-transformer-remark`,
     options: {
       plugins: [
         "gatsby-remark-autolink-headers",
   +       {
   +         resolve: "shiki-twoslash",
   +         options: {
   +            theme: "nord",
   +         }
   +       },
         "gatsby-remark-copy-linked-files",
         "gatsby-remark-smartypants",
       ],
     },
   }
   

   If you have gatsby-remark-prismjs in, delete it from the config and run yarn remove gatsby-remark-prismjs.

3. Add the CSS

   This CSS comes from the TypeScript website's scss

   You should consider it a base to work from, rather than a perfect for every project reference.

   /* Code blocks look like: 
   <pre class='shiki twoslash'>
    <div class='language-id>[lang-id]</div>
    <div class='code-container'>
       <code>[the code as a series of spans]</code>
    </div>
   </pre> 
   */
   pre {
     /* In theory shiki will overwrite these, but this is to make sure there are defaults */
     background-color: white;
     color: black;
     /* Give it some space to breathe */
     padding: 12px;
     /* All code samples get a grey border, twoslash ones get a different color */
     border-left: 1px solid #999;
     border-bottom: 1px solid #999;
     margin-bottom: 3rem;
     /* Important to allow the code to move horizontally; */
     overflow: auto;
     position: relative;
   }
   pre.shiki {
     overflow: initial;
   }
   /* So that folks know you can highlight */
   pre.twoslash {
     border-color: #719af4;
   }
   /* The code inside should scroll, but the overflow can't be on the shiki because it would not allow the relative positioning */
   pre .code-container {
     overflow: auto;
   }
   /* Handle scrolling, and showing code correctly */
   pre code {
     white-space: pre;
     -webkit-overflow-scrolling: touch;
   }
   /* Let errors use the outer shiki for their absolute sizing, and not be affected by the scrolling of the code */
   pre data-err {
     background: url("data:image/svg+xml,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%206%203'%20enable-background%3D'new%200%200%206%203'%20height%3D'3'%20width%3D'6'%3E%3Cg%20fill%3D'%23c94824'%3E%3Cpolygon%20points%3D'5.5%2C0%202.5%2C3%201.1%2C3%204.1%2C0'%2F%3E%3Cpolygon%20points%3D'4%2C0%206%2C2%206%2C0.6%205.4%2C0'%2F%3E%3Cpolygon%20points%3D'0%2C2%201%2C3%202.4%2C3%200%2C0.6'%2F%3E%3C%2Fg%3E%3C%2Fsvg%3E")
       repeat-x bottom left;
     padding-bottom: 3px;
   }
   /* In order to have the 'popped out' style design and to not break the layout
   /* we need to place a fake and un-selectable copy of the error which _isn't_ broken out
   /* behind the actual error message.
   /* This section keeps both of those in sync  */
   pre .error,
   pre .error-behind {
     margin-left: -20px;
     margin-top: 8px;
     margin-bottom: 4px;
     padding: 6px;
     padding-left: 14px;
     white-space: pre-wrap;
     display: block;
   }
   pre .error {
     position: absolute;
     background-color: #ffeeee;
     border-left: 2px solid #bf1818;
     width: calc(100% - 14px);
     /* Give the space to the error code  */
     display: flex;
     align-items: center;
     color: black;
   }
   pre .error .code {
     display: none;
   }
   pre .error-behind {
     user-select: none;
     color: #ffeeee;
   }
   data-lsp {
     /* Ensures there's no 1px jump when the hover happens above */
     border-bottom: 1px dotted transparent;
     /* Fades in unobtrusively */
     transition-timing-function: ease;
     transition: border-color 0.3s;
   }
   /* Respect people's wishes to not have animations */
   @media (prefers-reduced-motion: reduce) {
     data-lsp {
       transition: none;
     }
   }
   /** When you mouse over the pre, show the underlines */
   pre:hover data-lsp {
     border-color: #747474;
   }
   /** The tooltip-like which provides the LSP response */
   #twoslash-mouse-hover-info {
     background-color: #3f3f3f;
     color: #fff;
     text-align: left;
     padding: 5px 8px;
     border-radius: 2px;
     font-family: "JetBrains Mono", Menlo, Monaco, Consolas, Courier New, monospace;
     font-size: 14px;
     white-space: pre-wrap;
   }
   

4. Add the JS for hover info to your component:

   import React, { useEffect } from "react"
   import { setupTwoslashHovers } from "shiki-twoslash/dom";
   
   export default () => {
     // Add a the hovers
     useEffect(setupTwoslashHovers, [])
   
       // Normal JSX for your component
     return </>
   }
   

Verify

With that set up, start up your server and add a codeblock to a markdown file to see if it renders with highlights:

```json
{ "json": true }
```

If that works, then add a twoslash example:

```ts twoslash
interface IdLabel {id: number, /* some fields */ }
interface NameLabel {name: string, /* other fields */ }
type NameOrId = T extends number ? IdLabel : NameLabel;
// This comment should not be included

// ---cut---
function createLabel(idOrName: T): NameOrId {
  throw "unimplemented"
}

let a = createLabel("typescript");`
```

If the code sample shows as

function createLabel<T extends number | string>(idOrName: T): NameOrId<T> {
  throw "unimplemented"
}

let a = createLabel("typescript")

Then it worked, and you should be able to hover over createLabel to see it's types.

Plugin Config

This plugin passes the config options directly to Shiki. You probably will want to set theme.