vim-patch:8.2.2206: :exe command line completion only works for first argument

Problem:    :exe command line completion only works for first argument.
Solution:   Skip over text if more is following. (closes vim/vim#7546)
4941b5effd

Port "IS_WHITE_OR_NUL" macro from patch v8.2.0562
as "ascii_iswhite_or_nul()" inline function.

N/A patches for version.c:

vim-patch:8.2.0782: cannot build with Lua on MS-Windows

Problem:    Cannot build with Lua on MS-Windows.
Solution:   Add DLL symbol for luaL_Loadstring. (Ken Takata)
df1643a6a7

vim-patch:8.2.0856: CTRL-S stops output

Problem:    CTRL-S stops output.
Solution:   Invert the IXON flag. (closes vim/vim#6166)
928eec649b

vim-patch:8.2.1212: cannot build with Lua 5.4

Problem:    Cannot build with Lua 5.4.
Solution:   Use luaL_typeerror instead defining it. (closes vim/vim#6454)
5551b131da

vim-patch:8.2.2211: MS-Windows: can't load Python dll if not in the path

Problem:    MS-Windows: can't load Python dll if not in the path.
Solution:   Use the InstallPath registry entry. (Kelvin Lee, closes vim/vim#7540)
b2f9e0e2c5

src/nvim/ascii.h

@@ -89,6 +89,10 @@ static inline bool ascii_iswhite(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
 
+static inline bool ascii_iswhite_or_nul(int)
+  REAL_FATTR_CONST
+  REAL_FATTR_ALWAYS_INLINE;
+
 static inline bool ascii_isdigit(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
@@ -117,6 +121,14 @@ static inline bool ascii_iswhite(int c)
   return c == ' ' || c == '\t';
 }
 
+/// Checks if `c` is a space or tab character or NUL.
+///
+/// @see {ascii_isdigit}
+static inline bool ascii_iswhite_or_nul(int c)
+{
+  return ascii_iswhite(c) || c == NUL;
+}
+
 /// Check whether character is a decimal digit.
 ///
 /// Library isdigit() function is officially locale-dependent and, for

src/nvim/eval.c

@@ -2556,6 +2556,7 @@ void free_for_info(void *fi_void)
 
 
 void set_context_for_expression(expand_T *xp, char_u *arg, cmdidx_T cmdidx)
+  FUNC_ATTR_NONNULL_ALL
 {
   int got_eq = FALSE;
   int c;
@@ -2638,6 +2639,23 @@ void set_context_for_expression(expand_T *xp, char_u *arg, cmdidx_T cmdidx)
       }
     }
   }
+
+  // ":exe one two" completes "two"
+  if ((cmdidx == CMD_execute
+       || cmdidx == CMD_echo
+       || cmdidx == CMD_echon
+       || cmdidx == CMD_echomsg)
+      && xp->xp_context == EXPAND_EXPRESSION) {
+    for (;;) {
+      char_u *const n = skiptowhite(arg);
+
+      if (n == arg || ascii_iswhite_or_nul(*skipwhite(n))) {
+        break;
+      }
+      arg = skipwhite(n);
+    }
+  }
+
   xp->xp_pattern = arg;
 }
 

src/nvim/testdir/test_cmdline.vim

@@ -577,6 +577,17 @@ funct Test_cmdline_complete_languages()
   endif
 endfunc
 
+func Test_cmdline_complete_expression()
+  let g:SomeVar = 'blah'
+  for cmd in ['exe', 'echo', 'echon', 'echomsg']
+    call feedkeys(":" .. cmd .. " SomeV\<Tab>\<C-B>\"\<CR>", 'tx')
+    call assert_match('"' .. cmd .. ' SomeVar', @:)
+    call feedkeys(":" .. cmd .. " foo SomeV\<Tab>\<C-B>\"\<CR>", 'tx')
+    call assert_match('"' .. cmd .. ' foo SomeVar', @:)
+  endfor
+  unlet g:SomeVar
+endfunc
+
 func Test_cmdline_write_alternatefile()
   new
   call setline('.', ['one', 'two'])