# script

Learn about the script extension point.

{% hint style="warning" %}
Heads up!

When using `script`-based rules, you're limited to the standard Go [regex syntax](https://pkg.go.dev/regexp/syntax).
{% endhint %}

| Name     | Type     | Description                                            |
| -------- | -------- | ------------------------------------------------------ |
| `script` | `string` | The [Tengo](https://tengolang.com/) script to execute. |

`script` allows for the creation of arbitrary logic-based rules using [Tengo](https://tengolang.com/), a Go-like scripting language.

```yaml
extends: script
message: 'Consider inserting a new section heading at this point.'
link: https://tengolang.com
scope: raw
script: MyScript.tengo
```

Where `MyScript.tengo` is a file containing the Tengo script to execute stored at `$StypesPath/config/scripts`.

````go
text := import("text")

matches := []
// at most 3 paragraphs per section
p_limit := 3

// Remove all instances of code blocks
// since we don't want to count inter-block
// newlines as a new paragraph.
document := text.re_replace("(?s) *(\n```.*?```\n)", scope, "")

count := 0
for line in text.split(document, "\n") {
    if text.has_prefix(line, "#") {
        count = 0 // New section; reset count
    } else if count > p_limit {
        start := text.index(scope, line)
        matches = append(matches, {begin: start, end: start + len(line)})
        count = 0
    } else if text.trim_space(line) == "" {
        count += 1
    }
}
````

{% stepper %}
{% step %}
Use Tengo’s [`text`](https://github.com/d5/tengo/blob/master/docs/stdlib-text.md) module, which provides a number of string- and regex-related utility functions.
{% endstep %}

{% step %}
Process the content in the `scope` variable. `scope` contains text based on the `scope: <scope>` setting for the rule. For more information, see [Scoping](/topics/scopes.md).
{% endstep %}

{% step %}
Populate the `matches` array with rule matches. Each match must be a map with the keys:

* `begin`: where the match begins in the content provided by the `scope` variable.
* `end`: where the match ends in the content provided by the `scope` variable.
  {% endstep %}
  {% endstepper %}

[sequence](/checks/sequence.md) [suggest](/fixes/suggest.md)


---

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