Begin language service readme

actions-languageservice/README.md

@@ -1 +1,103 @@
-This contains the logic for the GitHub Actions workflows language server.
+# actions-languageservice
+
+This package contains the logic for the GitHub Actions workflows language server.
+
+## Installation
+
+The [package](https://www.npmjs.com/package/@actions/languageservice) contains TypeScript types and compiled ECMAScript modules.
+
+```bash
+$ npm install @actions/languageservice
+```
+
+## Usage
+
+### Basic usage
+
+#### Concepts
+
+The language service features use three sources of information:
+
+* a built-in static schema for the workflow YAML file
+* _value providers_ which can dynamically add values to the schema, for example, the list of available labels for a repository when validating `runs-on`.
+* _context providers_ which can dynamically provide available contexts used in [expressions](https://docs.github.com/actions/reference/context-and-expression-syntax-for-github-actions#about-contexts-and-expressions). For example, the contents of the `github.event` context for a given workflow file.
+
+##### Value Providers
+
+TODO
+
+##### Context Providers
+
+TODO
+
+#### Validation
+
+Validate a workflow file, returns an array of [`Diagnostic`](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnostic) objects.
+
+```js
+const config: ValidationConfig = {
+  valueProviderConfig: valueProviders(sessionToken, repoContext, cache),
+  contextProviderConfig: contextProviders(sessionToken, repoContext, cache),
+};
+
+const result = await validate(textDocument, config); // result is an array of `Diagnostic`
+```
+
+#### Hover
+
+Get information when [hovering](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_hover) over a token in the workflow file.
+
+```js
+import {hover} from "@actions/languageservice";
+
+const document = {
+  uri: "file:///path/to/file",
+  getText: () => "on: push\n  jobs:\n    build:\n      runs-on: ubuntu-latest\n      steps:\n        - run: echo hello"
+};
+
+const hover = await hover(document, {line: 0, character: 1}); // { contents: { kind: "markdown", value: "The event that triggers the workflow" } }
+```
+
+#### Auto-completion
+
+TODO
+
+## Contributing
+
+See [CONTRIBUTING.md](../CONTRIBUTING.md) at the root of the repository for general guidelines and recommendations.
+
+If you do want to contribute, please run [prettier](https://prettier.io/) to format your code and add unit tests as appropriate before submitting your PR.
+
+### Build
+
+```bash
+$ npm run build
+```
+
+or to watch for changes
+
+```bash
+$ npm run watch
+```
+
+### Test
+
+```bash
+$ npm test
+```
+
+or to watch for changes and run tests:
+
+```bash
+$ npm run test-watch
+```
+
+### Lint
+
+```bash
+$ npm run format-check
+```
+
+## License
+
+This project is licensed under the terms of the MIT open source license. Please refer to [MIT](../LICENSE) for the full terms.