如何在Emacs中实现类似Vim C-x C-l的整行补全？

当然可以！在Emacs里实现整行补全其实不难，刚好能满足你想要的「整行版dabbrev-expand」需求，和Vim里C-x C-l的效果一致。下面给你两种实用的方案：

方案一：自定义专属整行补全函数 #

你可以自己写一段Elisp代码，基于dabbrev的匹配逻辑，但专门针对整行内容处理。把这段代码加到你的Emacs配置文件（比如~/.emacs或者~/.emacs.d/init.el）里：

(defun my-complete-line ()
  "Complete the current line using matching lines from the buffer."
  (interactive)
  (let* ((current-line (buffer-substring-no-properties (line-beginning-position) (line-end-position)))
         (completion-ignore-case t)
         candidates)
    ;; 遍历缓冲区收集匹配的行
    (save-excursion
      (goto-char (point-min))
      (while (not (eobp))
        (let ((line (buffer-substring-no-properties (line-beginning-position) (line-end-position))))
          (when (and (not (equal line current-line))
                     (string-prefix-p current-line line))
            (add-to-list 'candidates line t))))
      (if candidates
          (progn
            (delete-region (line-beginning-position) (line-end-position))
            (insert (completing-read "Complete line: " candidates nil t current-line)))
        (message "No matching lines found")))))

;; 绑定快捷键，比如直接用和Vim一样的C-x C-l
(global-set-key (kbd "C-x C-l") 'my-complete-line)

这个函数的逻辑很清晰：

• 先抓取当前行的内容作为匹配前缀
• 遍历整个缓冲区，收集所有以当前行为前缀且不重复的行
• 弹出补全菜单让你选择，选中后直接替换当前行

方案二：整合到hippie-expand的扩展补全 #

如果你平时习惯用Emacs内置的hippie-expand智能补全工具，可以给它添加一个整行补全的源。把这段代码加到配置里：

(defun try-complete-line (old)
  "Hippie expand function to complete the current line."
  (unless old
    (let ((current-line (buffer-substring-no-properties (line-beginning-position) (line-end-position))))
      (setq hippie-expand-old-string current-line)
      (setq hippie-expand-point (point)))
    (goto-char (line-beginning-position)))
  (let ((candidates)
        (current-line hippie-expand-old-string))
    (save-excursion
      (goto-char (point-min))
      (while (not (eobp))
        (let ((line (buffer-substring-no-properties (line-beginning-position) (line-end-position))))
          (when (and (not (equal line current-line))
                     (string-prefix-p current-line line))
            (add-to-list 'candidates line t)))))
    (if candidates
        (progn
          (delete-region (line-beginning-position) (line-end-position))
          (insert (completing-read "Complete line: " candidates nil t current-line))
          t)
      nil)))

;; 把整行补全加入hippie-expand的候选列表
(add-to-list 'hippie-expand-try-functions-list 'try-complete-line t)

之后你用M-x hippie-expand（或者你绑定的快捷键，比如常见的M-/）时，工具会自动尝试整行补全，和其他补全逻辑无缝结合。

两种方案都能实现你要的效果，第一种更直接，一键触发；第二种适合已经习惯hippie-expand补全流程的用户，按需选择就好。

内容的提问来源于stack exchange，提问作者Lemurata