emacs

GNU Emacs

GNU Emacs is an extensible, customizable text editor and computing environment featuring built-in LSP integration (Eglot), Tree-sitter syntax parsing, and native compilation.

When to Use

Extensible & Fully Customizable Text Editing: Tailoring an entire computing and editing environment in Emacs Lisp (Elisp).
Org Mode Productivity & Note-Taking: Authoring structured notes, agendas, literate programming, and task management.
Modal Editing with Evil Mode (Doom Emacs): Combining Vim modal muscle memory with Emacs extensibility.
Language Server Protocol (LSP) with Eglot: High-speed, built-in code navigation, completion, and diagnostic checking.

Quick Start

;; ~/.emacs.d/init.el - Essential modern starter configuration
(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
(package-initialize)

(unless (package-installed-p 'use-package) (package-refresh-contents) (package-install 'use-package))

(setq inhibit-startup-message t) (global-display-line-numbers-mode t)


## Core Concepts

### Modern Emacs Configuration with use-package & Eglot

Configuring modern package management and built-in LSP:

```elisp
;; ~/.emacs.d/init.el
(require 'package)
(setq package-archives '(("melpa" . "https://melpa.org/packages/")
                         ("gnu" . "https://elpa.gnu.org/packages/")))
(package-initialize)

;; Install and configure use-package
(unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package))
(require 'use-package)
(setq use-package-always-ensure t)

;; Built-in Eglot LSP configuration
(use-package eglot
  :ensure nil ; Built into Emacs 29+
  :hook ((rust-ts-mode . eglot-ensure)
         (python-ts-mode . eglot-ensure)
         (typescript-ts-mode . eglot-ensure))
  :config
  (setq eglot-autoshutdown t))

;; Fast completion with Corfu and Vertico
(use-package vertico
  :init
  (vertico-mode 1))

(use-package corfu
  :init
  (global-corfu-mode 1))

Org Mode Literate Programming

Executing embedded code blocks within documents:

* Technical Report
#+BEGIN_SRC python :results output
data = [12, 45, 67, 89, 34]
print(f"Average: {sum(data)/len(data):.2f}")
#+END_SRC

#+RESULTS:
: Average: 49.40

Magit: Git Porcelain for Emacs

Keyboard-driven Git operations (M-x magit-status):

s: Stage file or hunk
c c: Commit staged changes
P u: Push to upstream remote
b b: Switch branch interactively

Common Patterns

LSP Mode with Eglot (Built-in) for Fast Code Intelligence

Problem: Slow auto-completion and language server lag in heavy community frameworks.

Solution: Use built-in lightweight eglot:

;; Enable Eglot for Rust, Python, and TypeScript modes
(use-package eglot
  :ensure t
  :hook ((rust-mode . eglot-ensure)
         (python-mode . eglot-ensure)
         (typescript-ts-mode . eglot-ensure)))

Best Practices

Do:

Target Emacs 29/30+ with native compilation (--with-native-compilation) and built-in Tree-sitter modes.
Use use-package with :defer t to keep Emacs startup time under 0.5 seconds.
Prefer built-in eglot over heavy external LSP packages for low memory overhead.
Use Magit for Git management; it is widely considered the best Git interface in the industry.

Don't:

Add package installation logic without :ensure t or guard checks in use-package.
Leave garbage collection thresholds set too low; bump gc-cons-threshold during startup.
Block the Emacs main thread with synchronous network requests; use async processes.

Troubleshooting

Error	Cause	Solution
`Failed to download package: HTTPS connection error`	Outdated TLS/GnuTLS libraries on system or expired certificate.	Set `(setq gnutls-algorithm-priority "NORMAL:-VERS-TLS1.3")` if needed.
`Spawning language server failed: executable not found`	Target LSP server (e.g. `pyright`, `rust-analyzer`) not in system PATH.	Install language server and verify `exec-path-from-shell` package.
`Emacs startup taking > 5 seconds`	Synchronous package downloads and uncompiled Elisp during init.	Profile startup with `emacs --profile` and use `use-package :defer t`.

References

GNU Emacs Manual