refactor(diagnostic): Remove arguments for explainError

BREAKING CHANGE: Running :rustLsp explainError will now only explain
error on current line, users are suggested to use
vim.diagnostic.goto_prev() and vim.diagnostic.goto_next() for
navigation, as stated in issue
mrcjkb#603 and
mrcjkb#599

lua/rustaceanvim/commands/diagnostic.lua

@@ -54,111 +54,6 @@ local function set_close_keymaps(bufnr)
   vim.keymap.set('n', '<Esc>', close_hover, { buffer = bufnr, noremap = true, silent = true })
 end
 
-function M.explain_error()
-  if vim.fn.executable(rustc) ~= 1 then
-    vim.notify('rustc is needed to explain errors.', vim.log.levels.ERROR)
-    return
-  end
-
-  local diagnostics = vim
-    .iter(vim.diagnostic.get(0, {}))
-    ---@param diagnostic vim.Diagnostic
-    :filter(function(diagnostic)
-      return diagnostic.code ~= nil
-        and diagnostic.source == 'rustc'
-        and diagnostic.severity == vim.diagnostic.severity.ERROR
-    end)
-    :totable()
-  if #diagnostics == 0 then
-    vim.notify('No explainable errors found.', vim.log.levels.INFO)
-    return
-  end
-  local win_id = vim.api.nvim_get_current_win()
-  local opts = {
-    cursor_position = vim.api.nvim_win_get_cursor(win_id),
-    severity = vim.diagnostic.severity.ERROR,
-    wrap = true,
-  }
-  local found = false
-  local diagnostic
-  local pos_map = {}
-  ---@type string
-  local pos_id = '0'
-  repeat
-    diagnostic = vim.diagnostic.get_next(opts)
-    pos_map[pos_id] = diagnostic
-    if diagnostic == nil then
-      break
-    end
-    found = diagnostic.code ~= nil and diagnostic.source == 'rustc'
-    local pos = { diagnostic.lnum, diagnostic.col }
-    -- check if there is an explainable error at the same location
-    if not found then
-      local cursor_diagnostics = vim.tbl_filter(function(diag)
-        return pos[1] == diag.lnum and pos[2] == diag.col
-      end, diagnostics)
-      if #cursor_diagnostics ~= 0 then
-        diagnostic = cursor_diagnostics[1]
-        found = true
-        break
-      end
-    end
-    pos_id = vim.inspect(pos)
-    -- diagnostics are (0,0)-indexed but cursors are (1,0)-indexed
-    opts.cursor_position = { pos[1] + 1, pos[2] }
-    local searched_all = pos_map[pos_id] ~= nil
-  until diagnostic == nil or found or searched_all
-  if not found then
-    -- Fall back to first diagnostic
-    diagnostic = diagnostics[1]
-    local pos = { diagnostic.lnum, diagnostic.col }
-    opts.cursor_position = pos
-    return
-  end
-
-  ---@param sc vim.SystemCompleted
-  local function handler(sc)
-    if sc.code ~= 0 or not sc.stdout then
-      vim.notify('Error calling rustc --explain' .. (sc.stderr and ': ' .. sc.stderr or ''), vim.log.levels.ERROR)
-      return
-    end
-    local output = sc.stdout:gsub('```', '```rust', 1)
-    local markdown_lines = vim.lsp.util.convert_input_to_markdown_lines(output, {})
-    local float_preview_lines = vim.deepcopy(markdown_lines)
-    table.insert(float_preview_lines, 1, '---')
-    table.insert(float_preview_lines, 1, '1. Open in split')
-    vim.schedule(function()
-      local bufnr, winnr = vim.lsp.util.open_floating_preview(
-        float_preview_lines,
-        'markdown',
-        vim.tbl_extend('keep', config.tools.float_win_config, {
-          focus_id = 'rustc-explain-error',
-          close_events = { 'CursorMoved', 'BufHidden', 'InsertCharPre' },
-        })
-      )
-      _window_state.float_winnr = winnr
-      set_close_keymaps(bufnr)
-      set_split_open_keymap(bufnr, winnr, function()
-        -- set filetype to rust for syntax highlighting
-        vim.bo[_window_state.latest_scratch_buf_id].filetype = 'rust'
-        -- write the expansion content to the buffer
-        vim.api.nvim_buf_set_lines(_window_state.latest_scratch_buf_id, 0, 0, false, markdown_lines)
-      end)
-
-      if config.tools.float_win_config.auto_focus then
-        vim.api.nvim_set_current_win(winnr)
-      end
-    end)
-  end
-
-  -- Save position in the window's jumplist
-  vim.cmd("normal! m'")
-  vim.api.nvim_win_set_cursor(win_id, { diagnostic.lnum + 1, diagnostic.col })
-  -- Open folds under the cursor
-  vim.cmd('normal! zv')
-  vim.system({ rustc, '--explain', tostring(diagnostic.code) }, nil, vim.schedule_wrap(handler))
-end
-
 function M.explain_error_current_line()
   if vim.fn.executable(rustc) ~= 1 then
     vim.notify('rustc is needed to explain errors.', vim.log.levels.ERROR)

lua/rustaceanvim/commands/init.lua

@@ -60,21 +60,8 @@ local rustlsp_command_tbl = {
     end,
   },
   explainError = {
-    impl = function(args)
-      local subcmd = args[1] or 'cycle'
-      if subcmd == 'cycle' then
-        require('rustaceanvim.commands.diagnostic').explain_error()
-      elseif subcmd == 'current' then
+    impl = function()
         require('rustaceanvim.commands.diagnostic').explain_error_current_line()
-      else
-        vim.notify(
-          'explainError: unknown subcommand: ' .. subcmd .. " expected 'cycle' or 'current'",
-          vim.log.levels.ERROR
-        )
-      end
-    end,
-    complete = function()
-      return { 'cycle', 'current' }
     end,
   },
   relatedDiagnostics = {