vim-patch:8.2.3615: wrong indent in first line if re-formatting with indent expr

Problem:    When re-formatting with an indent expression the first line of a
            paragraph may get the wrong indent. (Martin F. Krafft)
Solution:   Apply the correct indenting function for the first line.
            (Christian Brabandt, closes vim/vim#9150, closes vim/vim#9056)
818ff25cd1

src/nvim/edit.c

@@ -7330,7 +7330,7 @@ static void replace_do_bs(int limit_col)
 }
 
 /// Check that C-indenting is on.
-static bool cindent_on(void)
+bool cindent_on(void)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
   return !p_paste && (curbuf->b_p_cin || *curbuf->b_p_inde != NUL);

src/nvim/ops.c

@@ -4547,9 +4547,20 @@ void format_lines(linenr_T line_count, int avoid_fex)
        */
       if (is_end_par || force_format) {
         if (need_set_indent) {
+          int indent = 0;  // amount of indent needed
+
           // replace indent in first line with minimal number of
           // tabs and spaces, according to current options
-          (void)set_indent(get_indent(), SIN_CHANGED);
+          if (curbuf->b_p_lisp) {
+            indent = get_lisp_indent();
+          } else {
+            if (cindent_on()) {
+              indent = *curbuf->b_p_inde != NUL ? get_expr_indent() : get_c_indent();
+            } else {
+              indent = get_indent();
+            }
+          }
+          (void)set_indent(indent, SIN_CHANGED);
         }
 
         // put cursor on last non-space

src/nvim/testdir/test_indent.vim

@@ -165,4 +165,79 @@ func Test_modeline_indent_expr()
   call delete('Xfile.txt')
 endfunc
 
+func Test_indent_func_with_gq()
+  
+  function GetTeXIndent()
+    " Sample indent expression for TeX files
+    let lnum = prevnonblank(v:lnum - 1)
+    " At the start of the file use zero indent.
+    if lnum == 0
+      return 0
+    endif
+    let line = getline(lnum)
+    let ind = indent(lnum)
+    " Add a 'shiftwidth' after beginning of environments.
+    if line =~ '\\begin{center}' 
+      let ind = ind + shiftwidth()
+    endif
+    return ind
+  endfunction
+
+  new
+  setl et sw=2 sts=2 ts=2 tw=50 indentexpr=GetTeXIndent()
+  put =[  '\documentclass{article}', '', '\begin{document}', '',
+        \ 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce ut enim non',
+        \ 'libero efficitur aliquet. Maecenas metus justo, facilisis convallis blandit',
+        \ 'non, semper eu urna. Suspendisse diam diam, iaculis faucibus lorem eu,',
+        \ 'fringilla condimentum lectus. Quisque euismod diam at convallis vulputate.',
+        \ 'Pellentesque laoreet tortor sit amet mauris euismod ornare. Sed varius',
+        \ 'bibendum orci vel vehicula. Pellentesque tempor, ipsum et auctor accumsan,',
+        \ 'metus lectus ultrices odio, sed elementum mi ante at arcu.', '', '\begin{center}', '',
+        \ 'Proin nec risus consequat nunc dapibus consectetur. Mauris lacinia est a augue',
+        \ 'tristique accumsan. Morbi pretium, felis molestie eleifend condimentum, arcu',
+        \ 'ipsum congue nisl, quis euismod purus libero in ante. Donec id semper purus.',
+        \ 'Suspendisse eget aliquam nunc. Maecenas fringilla mauris vitae maximus',
+        \ 'condimentum. Cras a quam in mi dictum eleifend at a lorem. Sed convallis',
+        \ 'ante a commodo facilisis. Nam suscipit vulputate odio, vel dapibus nisl',
+        \ 'dignissim facilisis. Vestibulum ante ipsum primis in faucibus orci luctus et',
+        \ 'ultrices posuere cubilia curae;', '', '']
+  1d_
+  call cursor(5, 1)
+  ka
+  call cursor(15, 1)
+  kb
+  norm! 'agqap
+  norm! 'bgqap
+  let expected = [ '\documentclass{article}', '', '\begin{document}', '',
+        \ 'Lorem ipsum dolor sit amet, consectetur adipiscing',
+        \ 'elit. Fusce ut enim non libero efficitur aliquet.',
+        \ 'Maecenas metus justo, facilisis convallis blandit',
+        \ 'non, semper eu urna. Suspendisse diam diam,',
+        \ 'iaculis faucibus lorem eu, fringilla condimentum',
+        \ 'lectus. Quisque euismod diam at convallis',
+        \ 'vulputate.  Pellentesque laoreet tortor sit amet',
+        \ 'mauris euismod ornare. Sed varius bibendum orci',
+        \ 'vel vehicula. Pellentesque tempor, ipsum et auctor',
+        \ 'accumsan, metus lectus ultrices odio, sed',
+        \ 'elementum mi ante at arcu.', '', '\begin{center}', '',
+        \ '  Proin nec risus consequat nunc dapibus',
+        \ '  consectetur. Mauris lacinia est a augue',
+        \ '  tristique accumsan. Morbi pretium, felis',
+        \ '  molestie eleifend condimentum, arcu ipsum congue',
+        \ '  nisl, quis euismod purus libero in ante. Donec',
+        \ '  id semper purus.  Suspendisse eget aliquam nunc.',
+        \ '  Maecenas fringilla mauris vitae maximus',
+        \ '  condimentum. Cras a quam in mi dictum eleifend',
+        \ '  at a lorem. Sed convallis ante a commodo',
+        \ '  facilisis. Nam suscipit vulputate odio, vel',
+        \ '  dapibus nisl dignissim facilisis. Vestibulum',
+        \ '  ante ipsum primis in faucibus orci luctus et',
+        \ '  ultrices posuere cubilia curae;', '', '']
+  call assert_equal(expected, getline(1, '$'))
+
+  bwipe!
+  delmark ab
+  delfunction GetTeXIndent 
+endfu
+
 " vim: shiftwidth=2 sts=2 expandtab