gen_ex_cmds.lua: build the command table

Lua port of create_cmdidxs.vim from 8.0.0572

N/A:
vim-patch:8.0.0572: building the command table requires Perl

Problem:    Building the command table requires Perl.
Solution:   Use a Vim script solution. (Dominique Pelle, closes vim/vim#1641)
6de5e12601

src/nvim/ex_docmd.c

@@ -155,8 +155,6 @@ struct dbg_stuff {
 # include "ex_cmds_defs.generated.h"
 #endif
 
-static const int command_count = 539;
-
 static char_u dollar_command[2] = {'$', 0};
 
 static void save_dbg_stuff(struct dbg_stuff *dsp)
@@ -2265,8 +2263,11 @@ static char_u * do_one_cmd(char_u **cmdlinep,
   need_rethrow = check_cstack = FALSE;
 
 doend:
-  if (curwin->w_cursor.lnum == 0)       /* can happen with zero line number */
+  // can happen with zero line number
+  if (curwin->w_cursor.lnum == 0) {
     curwin->w_cursor.lnum = 1;
+    curwin->w_cursor.col = 0;
+  }
 
   if (errormsg != NULL && *errormsg != NUL && !did_emsg) {
     if (flags & DOCMD_VERBOSE) {
@@ -2447,7 +2448,7 @@ static char_u *find_command(exarg_T *eap, int *full)
       const int c2 = eap->cmd[1];
 
       if (command_count != (int)CMD_SIZE) {
-        iemsg((char_u *)_("E943: Command table needs to be updated, run 'make cmdidxs'"));
+        iemsg((char *)_("E943: Command table needs to be updated, run 'make'"));
         getout(1);
       }
 

src/nvim/generators/gen_ex_cmds.lua

@@ -28,34 +28,41 @@ local lastchar = nil
 local i
 local cmd
 local first = true
-local prevfirstchar = nil
 
 local byte_a = string.byte('a')
 local byte_z = string.byte('z')
+local a_to_z = byte_z - byte_a + 1
 
-local cmdidxs = string.format([[
+-- Table giving the index of the first command in cmdnames[] to lookup
-static const cmdidx_T cmdidxs[%u] = {
+-- based on the first letter of a command.
-]], byte_z - byte_a + 2)
+local cmdidxs1_out = string.format([[
+static const uint16_t cmdidxs1[%u] = {
+]], a_to_z)
+-- Table giving the index of the first command in cmdnames[] to lookup
+-- based on the first 2 letters of a command.
+-- Values in cmdidxs2[c1][c2] are relative to cmdidxs1[c1] so that they
+-- fit in a byte.
+local cmdidxs2_out = string.format([[
+static const char_u cmdidxs2[%u][%u] = {
+/*             a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z */
+
+]], a_to_z, a_to_z)
 
 enumfile:write([[
 typedef enum CMD_index {
 ]])
 defsfile:write(string.format([[
+static const int command_count = %u;
+]], #defs))
+defsfile:write(string.format([[
 static CommandDefinition cmdnames[%u] = {
 ]], #defs))
+local cmds, cmdidxs1, cmdidxs2 = {}, {}, {}
 for i, cmd in ipairs(defs) do
   local enumname = cmd.enum or ('CMD_' .. cmd.command)
-  firstchar = string.byte(cmd.command)
+  local byte_cmd = cmd.command:sub(1, 1):byte()
-  if firstchar ~= prevfirstchar then
+  if byte_a <= byte_cmd and byte_cmd <= byte_z then
-    if (not prevfirstchar
+    table.insert(cmds, cmd.command)
-        or (byte_a <= firstchar      and firstchar     <= byte_z)
-        or (byte_a <= prevfirstchar  and prevfirstchar <= byte_z)) then
-      if not first then
-        cmdidxs = cmdidxs .. ',\n'
-      end
-      cmdidxs = cmdidxs .. '  ' .. enumname
-    end
-    prevfirstchar = firstchar
   end
   if first then
     first = false
@@ -71,6 +78,35 @@ for i, cmd in ipairs(defs) do
     .cmd_addr_type = %i
   }]], enumname, cmd.command, cmd.func, cmd.flags, cmd.addr_type))
 end
+for i = #cmds, 1, -1 do
+  local cmd = cmds[i]
+  -- First and second characters of the command
+  local c1 = cmd:sub(1, 1)
+  cmdidxs1[c1] = i - 1
+  if cmd:len() >= 2 then
+    local c2 = cmd:sub(2, 2)
+    local byte_c2 = string.byte(c2)
+    if byte_a <= byte_c2 and byte_c2 <= byte_z then
+      if not cmdidxs2[c1] then
+        cmdidxs2[c1] = {}
+      end
+      cmdidxs2[c1][c2] = i - 1
+    end
+  end
+end
+for i = byte_a, byte_z do
+  local c1 = string.char(i)
+  cmdidxs1_out = cmdidxs1_out .. '  /*  ' .. c1 .. '  */ ' .. cmdidxs1[c1] .. ',\n'
+  cmdidxs2_out = cmdidxs2_out .. '  /*  ' .. c1 .. '  */ {'
+  for j = byte_a, byte_z do
+    local c2 = string.char(j)
+    cmdidxs2_out = cmdidxs2_out ..
+      ((cmdidxs2[c1] and cmdidxs2[c1][c2])
+        and string.format('%3d', cmdidxs2[c1][c2] - cmdidxs1[c1])
+        or '  0') .. ','
+  end
+  cmdidxs2_out = cmdidxs2_out .. ' },\n'
+end
 defsfile:write([[
 
 };
@@ -81,8 +117,5 @@ enumfile:write([[
   CMD_USER_BUF = -2
 } cmdidx_T;
 ]])
-cmdidxs = cmdidxs .. [[
+defsfile:write(cmdidxs1_out .. '};\n')
-
+defsfile:write(cmdidxs2_out .. '};\n')
-};
-]]
-defsfile:write(cmdidxs)