fix(lsp): support -1 column in format range #40570

Problem:
`vim.lsp.buf.format()` accepts ranges using nvim indexing, where an
end column of -1 means end of line. LSP ranges cannot use that,
which is confusing for things like range formatting.

Solution:
Resolve -1 end columns to the line length before converting the range to
LSP positions.

runtime/doc/lsp.txt

@@ -1595,9 +1595,11 @@ format({opts})                                          *vim.lsp.buf.format()*
                   default: current selection in visual mode, `nil` in other
                   modes, formatting the full buffer) Range to format. Table
                   must contain `start` and `end` keys with {row,col} tuples
-                  using (1,0) indexing. Can also be a list of tables that
-                  contain `start` and `end` keys as described above, in which
-                  case `textDocument/rangesFormatting` support is required.
+                  using (1,0) indexing. The end column can be -1 to format
+                  through the end of the line. Can also be a list of tables
+                  that contain `start` and `end` keys as described above, in
+                  which case `textDocument/rangesFormatting` support is
+                  required.
                 • {timeout_ms}? (`integer`, default: `1000`) Time in
                   milliseconds to block for formatting requests. No effect if
                   async=true.

runtime/lua/vim/lsp/buf.lua

@@ -611,7 +611,7 @@ end
 ---
 --- Range to format.
 --- Table must contain `start` and `end` keys with {row,col} tuples using
---- (1,0) indexing.
+--- (1,0) indexing. The end column can be -1 to format through the end of the line.
 --- Can also be a list of tables that contain `start` and `end` keys as described above,
 --- in which case `textDocument/rangesFormatting` support is required.
 --- (Default: current selection in visual mode, `nil` in other modes,
@@ -664,6 +664,13 @@ function M.format(opts)
   local function set_range(client, params)
     ---  @param r {start:[integer,integer],end:[integer, integer]}
     local function to_lsp_range(r)
+      if r['end'][2] == -1 then
+        local end_line = api.nvim_buf_get_lines(bufnr, r['end'][1] - 1, r['end'][1], true)[1]
+        return {
+          start = vim.pos(bufnr, r.start[1] - 1, r.start[2]):to_lsp(client.offset_encoding),
+          ['end'] = vim.pos(bufnr, r['end'][1] - 1, #end_line):to_lsp(client.offset_encoding),
+        }
+      end
       return util.make_given_range_params(r.start, r['end'], bufnr, client.offset_encoding).range
     end
 

test/functional/plugin/lsp/buf_spec.lua

@@ -1343,6 +1343,52 @@ describe('vim.lsp.buf', function()
       }
     end)
 
+    it('formats range ending with -1 column', function()
+      exec_lua(create_server_definition)
+      local result = exec_lua(function()
+        local server = _G._create_server({
+          capabilities = {
+            documentRangeFormattingProvider = true,
+          },
+          handlers = {
+            ['textDocument/rangeFormatting'] = function(_, params, callback)
+              callback(nil, {
+                {
+                  range = params.range,
+                  newText = 'function fn(abc)\n  print("hello")',
+                },
+              })
+            end,
+          },
+        })
+        local bufnr = vim.api.nvim_get_current_buf()
+        local client_id = assert(vim.lsp.start({ name = 'dummy', cmd = server.cmd }))
+        vim.api.nvim_win_set_buf(0, bufnr)
+        vim.api.nvim_buf_set_lines(bufnr, 0, -1, true, {
+          'function fn(abc  )',
+          '  print("hello" )',
+          'end',
+        })
+        vim.lsp.buf.format({
+          bufnr = bufnr,
+          range = {
+            start = { 1, 0 },
+            ['end'] = { 2, -1 },
+          },
+        })
+        vim.lsp.get_client_by_id(client_id):stop()
+        return {
+          lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, true),
+          range = server.messages[3].params.range,
+        }
+      end)
+      eq({
+        start = { line = 0, character = 0 },
+        ['end'] = { line = 1, character = 17 },
+      }, result.range)
+      eq({ 'function fn(abc)', '  print("hello")', 'end' }, result.lines)
+    end)
+
     it('sends textDocument/rangesFormatting request to format multiple ranges', function()
       local expected_handlers = {
         { NIL, {}, { method = 'shutdown', client_id = 1 } },