docs/code-assistant/coding-standards.md

# Coding Standards and Best Practices

## 🚨 CRITICAL: JSDoc Type Annotation Requirements

**ALWAYS create comprehensive JSDoc headers for ALL functions and use specific types instead of generic "object".**

When creating or modifying JavaScript functions, you MUST:

1. **Add JSDoc headers to ALL functions** - No exceptions, even simple utility functions
2. **Use specific types instead of "object"** - TypeScript can infer most types; leverage this
3. **Import types from relevant modules** - Use `@import` statements for external types
4. **Add @param annotations with union types** - E.g., `@param {UserData|null}` not `@param {Object}`
5. **Add @returns annotations with specific types** - E.g., `@returns {Promise<void>}` not just `@returns`
6. **Type-cast variables when needed** - Use `/** @type {SpecificType|null} */` for variable declarations

**Examples of CORRECT JSDoc annotations:**

```javascript
/**
 * @import { UserData } from './authentication.js'
 * @import { LookupItem } from '../modules/file-data-utils.js'
 */

/**
 * Checks if user has specific role
 * @param {UserData|null} user - User object or null
 * @param {string} role - Role name to check
 * @returns {boolean} True if user has role
 */
function userHasRole(user, role) {
  return user && user.roles && user.roles.includes(role)
}

/**
 * Gets file metadata by hash
 * @param {string} hash - File hash identifier
 * @returns {LookupItem|null} File data or null if not found
 */
function getFileData(hash) {
  /** @type {LookupItem|null} */
  const fileData = getFileDataByHash(hash)
  return fileData
}
```

**AVOID these patterns:**
- `@param {Object}` - Too generic, use specific interface types
- `@param {object}` - Same issue, specify the actual structure
- Missing `@returns` on functions - Always specify return types
- Untyped variables - Use `@type` comments for complex assignments

This ensures TypeScript error-free code and provides excellent IDE autocompletion support.

## Python Development

- Always prefer pathlib `Path().as_posix()` over manually concatenating path strings or `os.path.join()`
- The backend auto-restarts when changes are detected - do not start, restart, or suggest restarting the server manually

## Frontend Development

### Shoelace Component Registration

When using new Shoelace components, ensure they are properly imported and exported in `app/src/ui.js`. Components not properly registered will have `visibility: hidden` due to the `:not(:defined)` CSS rule.

Example: if using `sl-tree-item`, import `SlTreeItem` from `@shoelace-style/shoelace/dist/components/tree-item/tree-item.js` and add it to the export list.

### Shoelace Icon Resources

When using Shoelace icons programmatically (via `icon` attribute or StatusText widget) where the literal `<sl-icon name="icon-name"></sl-icon>` is not present in the codebase, add a comment with the HTML literal to ensure the build system includes the icon resource:

```javascript
// <sl-icon name="icon-name"></sl-icon>
```

This is not needed when the icon tag already exists verbatim in templates or HTML.

### Debug Logging

When adding temporary debug statements for interactive testing, use `console.log("DEBUG ...")` instead of `logger.debug()`. Always prefix the message with "DEBUG" to make them easily searchable and removable.

Example:
```javascript
console.log("DEBUG Collection in options:", options.collection);
```

This allows easy filtering with browser dev tools and quick cleanup using search/replace.

### UI Name Resolution System

The UI name resolution system allows lookup of DOM elements by a chain of nested "name" attributes. In runtime, it is updated by calling `updateUi()` from ui.js. Then, elements can be referred to by `ui.<top-level-name>.<next-level-name>....` etc.

Each time a new element with a name is added to the DOM, `updateUi()` must be called again.

In code, this hierarchy must be manually added by JSDoc/TypeScript `@typedef` definitions to get autocompletion. TypeScript errors can indicate missing definitions - add them when needed.

## JSDoc/TypeScript Best Practices

The application uses plain JavaScript to avoid transpilation. All type annotations are in JSDoc comments.

To avoid TypeScript errors, follow these best practices:

- In `catch` blocks, use `String(error)` instead of `error.message` when the error message should be used in console messages, to avoid type checking overhead
- Use specific types instead of generic `object` or `Object`
- Always document return types, even for `void` functions
- Import types from their source modules using `@import`

## General Code Conventions

When making changes to files, first understand the file's code conventions. Mimic code style, use existing libraries and utilities, and follow existing patterns.

- **NEVER assume that a library is available**, even if well known. Check `package.json` or neighboring files first
- When creating a new component, look at existing components to understand framework choice, naming conventions, typing, and other conventions
- When editing code, examine surrounding context (especially imports) to understand the code's choice of frameworks and libraries
- Always follow security best practices. Never introduce code that exposes or logs secrets and keys. Never commit secrets or keys to the repository