Line numbers

[jbrooksuk]

Would it be possible to add support for line numbers?

Bonus points for not restricting you to auto-generate them either. For example, when showing a Git diff, the line numbers will change.

[octref]

It's possible, just need to add that to the HTML renderer.

You can do it too if you have time:

const shiki = require('shiki')

shiki.getHighlighter({
  theme: 'nord'
}).then(highlighter => {
  const tokens = highlighter.codeToThemedTokens(`console.log('shiki');`, 'js')
  const html = shiki.renderToHtml(tokens) // default renderer, replace with yours
})

[alexpeattie]

As an alternative to writing a custom renderToHtml function: since v0.2.3 each line is wrapped in a <span class='line'> which makes it quite easy to do line numbering using CSS counters. I added some CSS like this:

code {
  counter-reset: step;
  counter-increment: step 0;
}

code .line::before {
  content: counter(step);
  counter-increment: step;
  width: 1rem;
  margin-right: 1.5rem;
  display: inline-block;
  text-align: right;
  color: rgba(115,138,148,.4)
}

Which yields:

[bramus]

Building further upon @alexpeattie's code: using Custom Properties you can set a different start number.

code {
	counter-reset: step;
	counter-increment: step calc(var(--start, 1) - 1);
}

<code style="--start: 13;">…</code>

If no --start is set, it will fall back to start numbering at 1.

Demo: https://codepen.io/bramus/pen/mdmmdQB

(You might want to opt for a more unique name for the Custom Property)

[lloydjatkinson]

Given that line numbers is pretty much a normal expectation of syntax highlighting and that this issue has been open for three and a half years now, could one of the above solutions be built in?

[heychazza]

Given that line numbers is pretty much a normal expectation of syntax highlighting and that this issue has been open for three and a half years now, could one of the above solutions be built in?

I'd also love to see code diff highlighting, so for example showing added and removed lines of code (with highlighting for whatever lang).

[ghost]

prefer the style of shiki, but compared with other similar plugins, such as Prism and highlight, they all have the line number function, hope shiki can also support it

[antfu]

Consider the solution #3 (comment) is quite solid and working well with the existing ecosystem, I think we could consider this is resolved. Otherwise, the newly introduced transformers API should allow this to be implemented on user land.

[tisonkun]

#3 (comment) looks good. While with astro, I found there is always a trailing <span class='line' /> rendered and it cause an extra dangling line number.

Not sure if it's an issue of Shiki or astro.

In index.mdx file -

```rust
let x = 42;
Ok(x)
```

Rendered:

<pre class="astro-code github-light" style="background-color:#fff;color:#24292e;overflow-x:auto" tabindex="0"><code><span class="line"><span style="color:#D73A49">let</span><span style="color:#24292E"> x </span><span style="color:#D73A49">=</span><span style="color:#005CC5"> 42</span><span style="color:#24292E">;</span></span>
<span class="line"><span style="color:#6F42C1">Ok</span><span style="color:#24292E">(x)</span></span>
<span class="line"></span></code></pre>

Result:

[seancheung]

#3 (comment) looks good. While with astro, I found there is always a trailing <span class='line' /> rendered and it cause an extra dangling line number.

Not sure if it's an issue of Shiki or astro.

In index.mdx file -

```rust
let x = 42;
Ok(x)

Rendered:

let x = 42;
Ok(x)

Result:

<img alt="image" width="933" src="https://private-user-images.githubusercontent.com/18818196/318681030-35b5acb6-282f-44d5-8037-b0c472c81aab.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.dM1XLx0LgJPx7ayjL21-JEg7hpg_4ArrJ3VdpDe4MCA">

Same dangling line here. You can filter it out:

code > .line:not(:last-child)::before {
 /* styling */
}

[MatthewAry]

@antfu Would love to see this solution on the Shiki docs.

[antfu]

PR welcome :)

[lloydjatkinson]

@antfu Would love to see this solution on the Shiki docs.

You can also checkout https://expressive-code.com/ which uses Shiki and has a line number option

[jimfilippou]

Extending on @alexpeattie's answer, if you're looking to get rid of the last line that this code adds, feel free to use the following code.

code .line:last-child::before {
  content: 'none';
}

[eniodev]

@seancheung another way of getting rid of that extra line:

code .line:last-child:empty::before {
  content: none;
  counter-increment: none;
}

[michael-andreuzza]

As an alternative to writing a custom renderToHtml function: since v0.2.3 each line is wrapped in a <span class='line'> which makes it quite easy to do line numbering using CSS counters. I added some CSS like this:

code {
  counter-reset: step;
  counter-increment: step 0;
}

code .line::before {
  content: counter(step);
  counter-increment: step;
  width: 1rem;
  margin-right: 1.5rem;
  display: inline-block;
  text-align: right;
  color: rgba(115,138,148,.4)
}

Which yields:

You my day :-) Thank you.

[LekoArts]

Regarding the dangling new line when used in Astro:

You can remove it like so in your astro.config.ts

import { defineConfig } from 'astro/config'

// https://astro.build/config
export default defineConfig({
	markdown: {
		syntaxHighlight: 'shiki',
		shikiConfig: {
			transformers: [
				{
					preprocess(code) {
						if (code.endsWith('\n')) {
							code = code.slice(0, -1)
						}

						return code
					},
				},
			],
		},
	},
})

[lilpolymath]

@antfu do you have any reservations on how the transformer for this should be implemented?