# ESLint plugins

Custom ESLint rules for DSpace Angular peculiarities.

## Overview

- Different file types must be handled by separate plugins. We support:
  - [TypeScript](./src/ts)
  - [HTML](./src/html)
- All rules are written in TypeScript and compiled into [`dist`](./dist)
  - The plugins are linked into the main project dependencies from here
  - These directories already contain the necessary `package.json` files to mark them as ESLint plugins
- The plugins are declared in [`.eslintrc.json`](../.eslintrc.json). Individual rules can be configured or disabled there, like usual.
- Some useful links
  - [Developing ESLint plugins](https://eslint.org/docs/latest/extend/plugins)
  - [Custom rules in typescript-eslint](https://typescript-eslint.io/developers/custom-rules)
  - [Angular ESLint](https://github.com/angular-eslint/angular-eslint)

## Parsing project metadata in advance ~ TypeScript AST

While it is possible to retain persistent state between files during the linting process, it becomes quite complicated if the content of one file determines how we want to lint another file.
Because the two files may be linted out of order, we may not know whether the first file is wrong before we pass by the second. This means that we cannot report or fix the issue, because the first file is already detached from the linting context.

For example, we cannot consistently determine which components are themeable (i.e. have a `ThemedComponent` wrapper) while linting.
To work around this issue, we construct a registry of themeable components _before_ linting anything.
- We don't have a good way to hook into the ESLint parser at this time
- Instead, we leverage the actual TypeScript AST parser
  - Retrieve all `ThemedComponent` wrapper files by the pattern of their path (`themed-*.component.ts`)
  - Determine the themed component they're linked to (by the actual type annotation/import path, since filenames are prone to errors)
  - Store metadata describing these component pairs in a global registry that can be shared between rules
- This only needs to happen once, and only takes a fraction of a second (for ~100 themeable components)