IntelliSense

# ===== Where suggestions come from =====
# 1. Language servers (LSP): tsserver for TS/JS, gopls for Go, pyright for Python, etc.
# 2. Word-based suggestions: tokens from open buffers (fallback)
# 3. Snippet engines: user, workspace, extension snippets
# 4. Path / file completions
# 5. AI assistants (Copilot, Cursor) wrapping the above

# ===== Anatomy of a completion =====
# label, detail, documentation, insertText, kind, sortText
# kind drives the icon; sortText controls ordering

# ===== TypeScript: turn on the strictness you want =====
# tsconfig.json
{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true,
    "verbatimModuleSyntax": true,
    "isolatedModules": true,
    "resolveJsonModule": true,
    "types": ["node"]
  }
}
# IntelliSense quality scales with the strictness of your config.

# ===== Plain JS gets typed by JSDoc =====
/**
 * @param {{ id: string, total: number }} order
 * @returns {Promise<{ id: string, status: 'queued' | 'sent' }>}
 */
async function ship(order) { /* ... */ }
# Now JS files get autocomplete on the order param and the returned shape.

# ===== Trigger Suggest on demand =====
# Ctrl+Space  - manual trigger
# Ctrl+.      - quick fix / code actions (auto-import, add missing prop)
# F12         - go to definition
# Alt+F12     - peek
# Ctrl+T      - workspace symbols
# Ctrl+Shift+. (codeAction)  - rename, extract, organise imports

# ===== Snippets =====
# .vscode/test.code-snippets
{
  "Vitest test": {
    "scope": "typescript,javascript",
    "prefix": "vit",
    "body": [
      "import { describe, it, expect } from 'vitest';",
      "",
      "describe('${1:thing}', () => {",
      "  it('${2:does the thing}', () => {",
      "    $0",
      "  });",
      "});"
    ]
  }
}
# Tab stops with ${1:placeholder}, final cursor at $0.

# ===== Tame noisy completions =====
# settings.json
{
  "editor.suggest.localityBonus": true,
  "editor.acceptSuggestionOnEnter": "smart",
  "editor.suggest.preview": true,
  "editor.parameterHints.enabled": true,
  "editor.inlineSuggest.enabled": true,
  "typescript.preferences.importModuleSpecifier": "non-relative",
  "typescript.updateImportsOnFileMove.enabled": "always"
}

# ===== Diagnostics: when IntelliSense feels wrong =====
# - 'TypeScript: Restart TS Server'           - palette command after big refactors
# - Output panel -> 'TypeScript' channel      - shows tsserver errors
# - Check tsconfig 'include' / 'exclude'      - file may not be in the project
# - Multi-root workspaces: each root has its own tsserver

# ===== Patterns to internalise =====
# - Strict TS = better IntelliSense; relax only where you must
# - JSDoc in JS files is a budget version of TypeScript
# - Workspace snippets > user snippets for team conventions
# - Use auto-import organisation on save: 'editor.codeActionsOnSave'

# ===== Pitfalls =====
# - 'tsserver is slow' is usually 'tsconfig include is too broad'
# - Disabling strictness one-by-one until red squiggles disappear (mask real bugs)
# - Mixing CommonJS and ESM without isolatedModules -> wrong-completions
# - Open files outside the workspace fall back to word completion only

// IntelliSense: completions + hover docs + parameter hints.
// Triggered by typing or Ctrl + Space.
// Powered by the language server (TS, Pyright, gopls, rust-analyzer, …).