---
sidebar_position: 5
sidebar_label: Capabilities
---

<head>
  <title>Capabilities | Regal</title>
</head>

# Capabilities

By default, Regal will lint your policies using the
[capabilities](https://www.openpolicyagent.org/docs/deployments/#capabilities) of the latest version of OPA
known to Regal (i.e. the latest version of OPA at the time Regal was released). Sometimes you might want to tell Regal
that some rules aren't applicable to your project (yet!). For example, recommending the use of the
[strings.count](https://www.openpolicyagent.org/projects/regal/rules/idiomatic/use-strings-count) function doesn't make
much sense for users who for some reason are targeting a version of OPA before v0.67.0, as that's when that function was
introduced.

The opposite could also be true — new versions of OPA sometimes invalidate rules that were relevant in the past. For
example, having Regal check for
[implicit future keyword](https://www.openpolicyagent.org/projects/regal/rules/imports/implicit-future-keywords) imports
makes no sense post OPA 1.0, as importing "future" keywords are no longer needed.

Capabilities help you tell Regal which features to take into account, and rules with dependencies to capabilities
not available or not applicable in the given version will be skipped.

If you'd like to target a specific version of OPA, you can include a `capabilities` section in your configuration,
providing either a specific `version` of an `engine` (currently only `opa` supported):

```yaml
capabilities:
  from:
    engine: opa
    version: v0.58.0
```

You can also choose to import capabilities from a file:

```yaml
capabilities:
  from:
    file: build/capabilities.json
```

You can use `plus` and `minus` to add or remove built-in functions from the given set of capabilities:

```yaml
capabilities:
  from:
    engine: opa
    version: v0.58.0
  minus:
    builtins:
      # exclude rules that depend on the http.send built-in function
      - name: http.send
  plus:
    builtins:
      # make Regal aware of a custom "ldap.query" function
      - name: ldap.query
        type: function
        decl:
          args:
            - type: string
        result:
          type: object
```

## Loading Capabilities from URLs

Starting with Regal version v0.26.0, Regal can load capabilities from URLs with the `http`, or `https` schemes using
the `capabilities.from.url` config key. For example, to load capabilities from `https://example.org/capabilities.json`,
this configuration could be used:

```yaml
capabilities:
  from:
    url: https://example.org/capabilities.json
```

## Supported Engines

Regal includes capabilities files for the following engines:

| Engine | Website                                                      | Description       |
| ------ | ------------------------------------------------------------ | ----------------- |
| `opa`  | [OPA website](https://www.openpolicyagent.org/)              | Open Policy Agent |
| `eopa` | [EOPA repository](https://github.com/open-policy-agent/eopa) | EOPA              |
| `rq`   | [rq website](https://git.sr.ht/~charles/rq)                  | Rego Query (`rq`) |

**`rq` support note**: `rq` scripts must include `package` statements to be compatible with Regal.