How to highlight a symbol under the cursor and its references?

[arbitrary-dev]

In coc-nvim there was this:

" Highlight the symbol and its references when holding the cursor.
autocmd CursorHold * silent call CocActionAsync('highlight')

[antosha417]

In order to do it I have this in on_attach function

metals_config.on_attach = function(client, bufnr)
  if client.server_capabilities.documentHighlightProvider then
    vim.api.nvim_create_augroup("lsp_document_highlight", { clear = true })
    vim.api.nvim_create_autocmd('CursorHold', {
      buffer = bufnr,
      group = 'lsp_document_highlight',
      callback = vim.lsp.buf.document_highlight
    })
    vim.api.nvim_create_autocmd('CursorMoved', {
      buffer = bufnr,
      group = 'lsp_document_highlight',
      callback = vim.lsp.buf.clear_references
    })
 end
end

[antosha417]

I use it not only with metals but with other language servers too. Sumneko lua, for example, supports it

[arbitrary-dev]

Still highlighting didn't show up for me.
Yet now I have this in my ~/.config/nvim/lua/nvim-metals.lua:

metals_config.on_attach = function(client, bufnr)
  require("metals").setup_dap()

  -- Adds symbol and its references highlighting
  if client.server_capabilities.documentHighlightProvider then
    api.nvim_create_augroup("lsp_document_highlight", { clear = true })
    api.nvim_create_autocmd('CursorHold', {
      buffer = bufnr,
      group = 'lsp_document_highlight',
      callback = vim.lsp.buf.document_highlight
    })
    api.nvim_create_autocmd('CursorMoved', {
      buffer = bufnr,
      group = 'lsp_document_highlight',
      callback = vim.lsp.buf.clear_references
    })
 end
end

[antosha417]

When your cursor is on the text that must be highlighted you can try to do :lua vim.lsp.buf.document_highlight() manually to check if it's working, without auto commands.

Also might be the case that your theme does not define highlight groups that are needed for this to work. You can try to set them manually like this:

vim.api.nvim_set_hl(0, 'LspReferenceText', { fg = "#000000", bg = "#FFFFFF", underline = true })
vim.api.nvim_set_hl(0, 'LspReferenceRead', { fg = "#000000", bg = "#FFFFFF", underline = true })
vim.api.nvim_set_hl(0, 'LspReferenceWrite', { fg = "#000000", bg = "#FFFFFF", underline = true })

[arbitrary-dev]

I added highlight groups and issued :lua vim.lsp.buf.document_highlight(), yet nothing happened.

[arbitrary-dev]

Ok, now that I've attached sources to my OpenJDK package, highlighting started to work at last. With a couple issues...