As a Neovim user who writes frequently, I want to use Neovim to check my grammar before posting it in my blog. In this post, I will compare several plugins used for grammar checking. Under the hood, they all use the opensource tool languagetool.

I will use macOS as example here. First, we need to install languagetool using homebrew:

brew install languagetool

It will also install open-jdk for you, but the path is not set by default. We have to set the open-jdk path manually:

export PATH="/usr/local/opt/openjdk/bin:$PATH"

Now I introduce several similar plugins that use languagetool for grammar checking.

LanguageTool.nvim

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update 2023-01-04: This plugins has been deprecated.

LanguageTool.nvim is neovim plugin that support asynchronous grammar checking. Install LanguageTool.nvim using vim-plug:

Plug 'vigoux/LanguageTool.nvim'

The only setting to make it work is:

let g:languagetool_server_jar="/usr/local/opt/languagetool/libexec/languagetool-server.jar"

Then open a file, run the following commands:

• :LanguageToolSetup: set up the languagetool server
• :LanguageToolCheck: check the current file
• :LanguageToolSummary: open a buffer and list all the grammar errors found in the file.

It seems that languagetool.nvim is fork of vim-LanguageTool, but the author intends to rewrite it to use more neovim-specific features.

Pros and cons

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• Pros: asynchronous grammar check. Has error highlighting.
• Cons: very slow.

vim-grammarous

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vim-grammarous is a more polished plugin.

Install:

Plug 'rhysd/vim-grammarous'

Run command: :GrammarousCheck to check grammar. It is asynchrous and non-blocking. When it finishes, it will notify the user in the statusline how many errros have been found.

It has options for you to configure the rules and categories for languagetool. See my config here. The explanation of categories and rules can be found here.

Pros and cons

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• Pros: Asynchronous and relatively fast. Various configs for you to tweak. Can specifiy the rules and categories to use for languagetool. Has error highlighting.
• Cons: not found yet.

vim-languagetool

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Another plugin: https://github.com/dpelle/vim-LanguageTool

Install with vim-plug:

Plug 'dpelle/vim-LanguageTool'

Only config you need:

let g:languagetool_jar="/usr/local/opt/languagetool/libexec/languagetool-commandline.jar"

Run command: :LanguageToolCheck to check grammar.

Pros and cons

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• Pros: Has error highlighting.
• Cons: It is not asynchronous, so it will hang until the results are produced.

vim-langtool

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Another similar plugin is vim-langtool. Install:

Plug 'Konfekt/vim-langtool'

Simple config:

let g:langtool_jar = '/usr/local/opt/languagetool/libexec/languagetool-commandline.jar'

Command to run: :LangTool.

Pros and cons

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• Pros: It will populate quickfix list with errors.
• Cons: It is not asynchronous. No error highlighting.

Ale

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Ale also support languagetool, add the following config:

let g:ale_linters = {
    \ 'python': ['pylint'],
    \ 'vim': ['vint'],
    \ 'cpp': ['clang'],
    \ 'c': ['clang'],
    \ 'markdown': ['languagetool']
\}

Then Ale will populate errors in the quickfix list.

Pros and cons

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• Pros: It will populate quickfix list with errors.
• Cons: No custom config available.

Common issues

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A common issue with languagetool is that it is intended for plain text, while filetypes like Markdown or LaTeX contains a lot of formatting commands or structure. So using languagetool directly on these filetypes produces a lot of false positives, as discussed here. However, it is not easy to fix this problem.

Conclusion

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Right now, it seems vim-grammarous the best plugin we can use for grammar checking.