`go-remove-unused-imports` cannot operate on unsaved buffer

[admacro]

Hi, I want to format and remove unnecessary imports when saving go buffers, so I wrote this little function to do it. However, I got an error saying "go-remove-unused-imports cannot operate on unsaved buffer".

(defun go-tidy-up ()
  (gofmt-before-save)
  (go-remove-unused-imports))
(add-hook 'before-save-hook 'go-tidy-up)

Error message

Calling gofmt: gofmt (-s -w /var/folders/z6/f1935z3x7wq9bwbfvfmnq5xw0000gn/T/gofmtwP3cch.go)
Applied gofmt
Error: (wrong-number-of-arguments #[(arg) "\212p\306\211���\307\303!\203����\303\310!\210\311\306\312\"\210\313 \203$�\314\315!\210\202Y�\316 \211�\306�\211�\203R�
@�\317!\210\320 \210��\203H�\321\322 \323 \"\210\202K�\324 \210
A\211�\204/�*\314\325�G\"\210	\205`�\303\326!,\207" [lines flymake-state cur-buffer flymake-mode import --dolist-tail-- nil boundp -1 save-some-buffers #[nil "�p\232\207" [cur-buffer] 2] buffer-modified-p message "Cannot operate on unsaved buffer" go-unused-imports-lines go--goto-line beginning-of-line comment-region line-beginning-position line-end-position go--delete-whole-line "Removed %d imports" 1 arg] 4 ("/Users/james/.emacs.d/elpa/go-mode-20200112.2140/go-mode.elc" . 61594) "P"] 0)

How can I make it work on unsaved buffers?

[muirdm]

go-remove-unused-imports is implemented by running go build or go test, so it isn't easy to make it work on unsaved buffers. If you install goimports and set gofmt-command to "goimports" then (gofmt-before-save) will handle imports as well and you no longer need go-remove-unused-imports.

Alternatively you can use lsp-mode and gopls and then use (lsp-organize-imports) to add/remove imports automatically. This will be the fastest and best long term approach, but requires some setup.

[admacro]

Hi muirdm, I do use lsp-mode with go, so I tried both methods. Both worked with the same effect. Thank you for suggesting the lsp-organize-imports command. It also does code formatting. One problem is now I can't make gofmt to simplify code (-s) on save. I searched around and found this related issue (golang issue#8759) to which there is no solution for now.

Here is the configuration.

;; The goimports approach
(setq gofmt-command "goimports") 
(add-hook 'before-save-hook 'gofmt-before-save)

or

;; The lsp approach
(add-hook 'before-save-hook 'lsp-organize-imports)

[muirdm]

Great! Note that in new versions of gopls lsp-organize-imports does not format the buffer (you need to also call lsp-format-buffer). Here is an issue for adding -s support to gopls.

[admacro]

Ah! Thanks again for the info. I just updated lsp-mode and added lsp-format-buffer to my config. 😃

;; the lsp approach
(add-hook 'before-save-hook
          (lambda ()
            (lsp-format-buffer)
            (lsp-organize-imports)))