bug: With format_on_save, timeout_ms must be set really high to have prettier working

[caneta]

Neovim version (nvim -v)

v0.10.0-dev

Operating system/version

WSL (Windows Subsystem Linux), Ubuntu 20.04.6 LTS

Add the debug logs

• I have set log_level = vim.log.levels.DEBUG and pasted the log contents below.

Log file

15:14:08[DEBUG] Running formatters on /home/user/my-project/Test.tsx: { "prettier" }
15:14:08[INFO] Run prettier on /home/user/my-project/Test.tsx
15:14:08[DEBUG] Run command: { "/home/user/my-project/node_modules/.bin/prettier", "--stdin-filepath", "/home/user/my-project/Test.tsx" }
15:14:08[DEBUG] Run CWD: /home/user/my-project
15:14:09[WARN] Formatter 'prettier' timeout
15:14:09[INFO] prettier exited with code 143
15:14:09[DEBUG] prettier stdout: { "" }
15:14:09[DEBUG] prettier stderr: { "" }

Describe the bug

I was expecting that the suggested conf of 500 ms had worked just fine, but I had a timeout.
The same result setting timeout_ms = nil, or removing it (so getting the default 1 sec, I guess.
It seems that like just the async option is not set to false as documented.

What is the severity of this bug?

minor (annoyance)

Steps To Reproduce

1. nvim /hove/user/my-project/Test.tsx
2. mess up the file
3. :w

Expected Behavior

I was expecting to have the file formatted by prettier and next saved by nvim. Only save succeed, and Conform reports the errors above. The only way to make it work is set to a very hight value like timeout_ms = 999999

[stevearc]

The default value of 500ms should be plenty of time for most formatters, and since formatting freezes the UI you probably don't want it to be larger than 500ms anyway. The quick fix for you that I would recommend is try using format_after_save instead of format_on_save (these are documented here).

Both format_on_save and format_after_save are just convenience wrappers that set up some autocmds for you. format_on_save uses a BufWritePre autocmd, which means that it executes in between the :w and Neovim actually writing the buffer to disk. For this reason, we must complete the formatting synchronously and block all processing in the meantime, otherwise Neovim will write the unformatted buffer to disk while we are still formatting.

format_after_save uses the BufWritePost autocmd. After Neovim writes the buffer to disk, we try to format the file. This happens asynchronously and does not need to block the UI. Once formatting is completed, it applies the changes to the buffer and re-saves the buffer to disk. If the user has modified the buffer at all between formatting start and formatting completion, we abandon the changes (to avoid overwriting your edits).

When your formatter takes a long time to run, the recommended way to handle this is via async formatting (such as format_after_save).

[caneta]

Crystal-clear @stevearc, thank you so much for your detailed answer. It works like a charm!

[ic-768]

I was struggling with this same issue, and what fixed this for me was using prettierd instead of prettier.
Much faster than prettier, and cleaner than running after save.

    conform.setup({
      formatters_by_ft = {
        javascript = { "eslint_d","prettierd" },
        typescript = { "eslint_d","prettierd" },
      }
     })

reddit post that turned me on to this