vim-patch:8.0.1090: cannot get the text under the cursor like v:beval_text

Problem:    cannot get the text under the cursor like v:beval_text
Solution:   Add <cexpr>.
65f084749b

runtime/doc/cmdline.txt

@@ -788,6 +788,11 @@ Also see |`=|.
 Note: these are typed literally, they are not special keys!
 	<cword>    is replaced with the word under the cursor (like |star|)
 	<cWORD>    is replaced with the WORD under the cursor (see |WORD|)
+	<cexpr>    is replaced with the word under the cursor, including more
+		   to form a C expression.  E.g., when the cursor is on "arg"
+		   of "ptr->arg" then the result is "ptr->arg"; when the
+		   cursor is on "]" of "list[idx]" then the result is
+		   "list[idx]".  This is used for |v:beval_text|.
 	<cfile>    is replaced with the path name under the cursor (like what
 		   |gf| uses)
 	<afile>    When executing autocommands, is replaced with the file name

src/nvim/ex_docmd.c

@@ -8392,23 +8392,25 @@ ssize_t find_cmdline_var(const char_u *src, size_t *usedlen)
     "%",
 #define SPEC_PERC   0
     "#",
-#define SPEC_HASH   1
+#define SPEC_HASH   (SPEC_PERC + 1)
     "<cword>",                          /* cursor word */
-#define SPEC_CWORD  2
+#define SPEC_CWORD  (SPEC_HASH + 1)
     "<cWORD>",                          /* cursor WORD */
-#define SPEC_CCWORD 3
+#define SPEC_CCWORD (SPEC_CWORD + 1)
+    "<cexpr>",                          // expr under cursor
+#define SPEC_CEXPR  (SPEC_CCWORD + 1)
     "<cfile>",                          /* cursor path name */
-#define SPEC_CFILE  4
+#define SPEC_CFILE  (SPEC_CEXPR + 1)
     "<sfile>",                          /* ":so" file name */
-#define SPEC_SFILE  5
+#define SPEC_SFILE  (SPEC_CFILE + 1)
     "<slnum>",                          /* ":so" file line number */
-#define SPEC_SLNUM  6
+#define SPEC_SLNUM  (SPEC_SFILE + 1)
     "<afile>",                          /* autocommand file name */
-# define SPEC_AFILE 7
+#define SPEC_AFILE  (SPEC_SLNUM + 1)
     "<abuf>",                           /* autocommand buffer number */
-# define SPEC_ABUF  8
+#define SPEC_ABUF   (SPEC_AFILE + 1)
     "<amatch>",                         /* autocommand match name */
-# define SPEC_AMATCH 9
+#define SPEC_AMATCH (SPEC_ABUF + 1)
   };
 
   for (size_t i = 0; i < ARRAY_SIZE(spec_str); ++i) {
@@ -8489,10 +8491,16 @@ eval_vars (
   /*
    * word or WORD under cursor
    */
-  if (spec_idx == SPEC_CWORD || spec_idx == SPEC_CCWORD) {
+  if (spec_idx == SPEC_CWORD
-    resultlen = find_ident_under_cursor(&result, (spec_idx == SPEC_CWORD
+      || spec_idx == SPEC_CCWORD
-                                                  ? (FIND_IDENT|FIND_STRING)
+      || spec_idx == SPEC_CEXPR) {
-                                                  : FIND_STRING));
+    resultlen = find_ident_under_cursor(
+        &result,
+        spec_idx == SPEC_CWORD
+        ? (FIND_IDENT | FIND_STRING)
+        : (spec_idx == SPEC_CEXPR
+           ? (FIND_IDENT | FIND_STRING | FIND_EVAL)
+           : FIND_STRING));
     if (resultlen == 0) {
       *errormsg = (char_u *)"";
       return NULL;

src/nvim/testdir/test_normal.vim

@@ -392,10 +392,22 @@ func! Test_normal10_expand()
   call setline(1, ['1', 'ifooar,,cbar'])
   2
   norm! $
-  let a=expand('<cword>')
+  call assert_equal('cbar', expand('<cword>'))
-  let b=expand('<cWORD>')
+  call assert_equal('ifooar,,cbar', expand('<cWORD>'))
-  call assert_equal('cbar', a)
+
-  call assert_equal('ifooar,,cbar', b)
+  call setline(1, ['prx = list[idx];'])
+  1
+  let expected = ['', 'prx', 'prx', 'prx',
+	\ 'list', 'list', 'list', 'list', 'list', 'list', 'list',
+	\ 'idx', 'idx', 'idx', 'idx',
+	\ 'list[idx]',
+	\ '];',
+	\ ]
+  for i in range(1, 16)
+    exe 'norm ' . i . '|'
+    call assert_equal(expected[i], expand('<cexpr>'), 'i == ' . i)
+  endfor
+
   " clean up
   bw!
 endfunc