@textlint/kernel/src/descriptor/README.md

textlint kernel is core logic by pure JavaScript.

# textlint kernel descriptor

A Descriptor class for kernel.

The Descriptor is a structure object of rules, filter rules, and plugins.

- The Descriptor is normalized/filtered object
    - without duplication
    - without disabled rules
- Create a Descriptor from textlintrc object
- Create a Descriptor from kernel options
- Analyze plugins and provide available extensions for linting 
- Analyze rules and provide normalized rule instance

## Usage

### Create a Descriptor from textlintrc object

```js
const descriptors = new TextlintKernelDescriptor({
    plugins: [
        {
            pluginId: "text",
            plugin: createDummyPlugin([".txt"])
        },
        {
            pluginId: "markdown",
            plugin: createDummyPlugin([".md"])
        }
    ],
    rules: [
        {
            ruleId: "example",
            rule: exampleRule
        }
    ],
    filterRules: []
});
// available extensions
assert.deepStrictEqual(descriptors.plugin.availableExtensions, [".txt", ".md"]);
// get plugin instance
const markdownProcessor = descriptors.findPluginDescriptorWithExt(".md");
assert.ok(markdownProcessor !== undefined);
// rules
assert.strictEqual(descriptors.rule.descriptors.length, 1);
```
### Parse with descriptor

```js
import { TextlintKernelDescriptor } from "@textlint/kernel";
import { exampleRule } from "textlint-rule-example";
import { createDummyPlugin } from "./util/create-dummy-plugin.js";
const descriptors = new TextlintKernelDescriptor({
    plugins: [
        {
            pluginId: "text",
            plugin: createDummyPlugin([".txt"])
        },
        {
            pluginId: "markdown",
            plugin: createDummyPlugin([".md"])
        }
    ],
    rules: [
        {
            ruleId: "example",
            rule: exampleRule
        }
    ],
    filterRules: []
});
// get plugin instance
const markdownProcessor = descriptors.findPluginDescriptorWithExt(".md");
assert.ok(markdownProcessor !== undefined);
const markdownPlugin = markdownProcessor.processor.processor(".md");
const result = await markdownPlugin.preProcess("# Hello World");
// TxtAST check
assert.ok(isTxtAST(result));
assert.strictEqual(result.type, "Document");
```