provider: Add support for python commands/functions

This uses the provider/scripting infrastructure to reintroduce python support
through the msgpack-rpc API.

A new 'initpython' option was added, and it must be set to a command that will
bootstrap the python provider the first time it's needed.

src/nvim/eval.c

@@ -6457,6 +6457,7 @@ static struct fst {
   {"prevnonblank",    1, 1, f_prevnonblank},
   {"printf",          2, 19, f_printf},
   {"pumvisible",      0, 0, f_pumvisible},
+  {"pyeval",          1, 1, f_pyeval},
   {"range",           1, 3, f_range},
   {"readfile",        1, 3, f_readfile},
   {"reltime",         0, 2, f_reltime},
@@ -11461,7 +11462,13 @@ static void f_pumvisible(typval_T *argvars, typval_T *rettv)
     rettv->vval.v_number = 1;
 }
 
-
+/*
+ * "pyeval()" function
+ */
+static void f_pyeval(typval_T *argvars, typval_T *rettv)
+{
+  script_host_eval("python_eval", argvars, rettv);
+}
 
 /*
  * "range()" function

src/nvim/ex_cmds2.c

@@ -789,6 +789,22 @@ void ex_profile(exarg_T *eap)
   }
 }
 
+void ex_python(exarg_T *eap)
+{
+  script_host_execute("python_execute", eap);
+}
+
+void ex_pyfile(exarg_T *eap)
+{
+  script_host_execute_file("python_execute_file", eap);
+}
+
+void ex_pydo(exarg_T *eap)
+{
+  script_host_do_range("python_do_range", eap);
+}
+
+
 /* Command line expansion for :profile. */
 static enum {
   PEXP_SUBCMD,          /* expand :profile sub-commands */

src/nvim/ex_cmds_defs.h

@@ -737,6 +737,12 @@ enum CMD_index
       RANGE|WHOLEFOLD|BANG|REGSTR|TRLBAR|ZEROR|CMDWIN|MODIFY),
   EX(CMD_pwd,             "pwd",          ex_pwd,
       TRLBAR|CMDWIN),
+  EX(CMD_python,          "python",       ex_python,
+      RANGE|EXTRA|NEEDARG|CMDWIN),
+  EX(CMD_pydo,            "pydo",         ex_pydo,
+      RANGE|DFLALL|EXTRA|NEEDARG|CMDWIN),
+  EX(CMD_pyfile,          "pyfile",       ex_pyfile,
+      RANGE|FILE1|NEEDARG|CMDWIN),
   EX(CMD_quit,            "quit",         ex_quit,
       BANG|TRLBAR|CMDWIN),
   EX(CMD_quitall,         "quitall",      ex_quit_all,

src/nvim/ex_docmd.c

@@ -1859,6 +1859,7 @@ static char_u * do_one_cmd(char_u **cmdlinep,
     case CMD_noautocmd:
     case CMD_noswapfile:
     case CMD_psearch:
+    case CMD_python:
     case CMD_return:
     case CMD_rightbelow:
     case CMD_silent:

src/nvim/option.c

@@ -963,6 +963,9 @@ static struct vimoption
   {"infercase",   "inf",  P_BOOL|P_VI_DEF,
    (char_u *)&p_inf, PV_INF,
    {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},
+  {"initpython","ipy",P_STRING|P_VI_DEF|P_SECURE,
+   (char_u *)&p_ipy, PV_NONE,
+   {(char_u *)NULL, (char_u *)0L} SCRIPTID_INIT},
   {"insertmode",  "im",   P_BOOL|P_VI_DEF|P_VIM,
    (char_u *)&p_im, PV_NONE,
    {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},

src/nvim/option_defs.h

@@ -630,6 +630,7 @@ EXTERN int p_write;             /* 'write' */
 EXTERN int p_wa;                /* 'writeany' */
 EXTERN int p_wb;                /* 'writebackup' */
 EXTERN long p_wd;               /* 'writedelay' */
+EXTERN char *p_ipy;             // 'initpython'
 
 /*
  * "indir" values for buffer-local opions.

src/nvim/os/provider.c

@@ -31,6 +31,12 @@ static struct feature {
   size_t name_length;
   uint64_t channel_id;
 } features[] = {
+  FEATURE("python",
+          &p_ipy,
+          "python_execute",
+          "python_execute_file",
+          "python_do_range",
+          "python_eval")
 };
 
 static Map(cstr_t, uint64_t) *registered_providers = NULL;

src/nvim/testdir/test86.in

@@ -9,7 +9,7 @@ STARTTEST
 :so small.vim
 :set encoding=latin1
 :set noswapfile
-:if !has('python') | e! test.ok | wq! test.out | endif
+:if !has('python') || has('neovim') | e! test.ok | wq! test.out | endif
 :lang C
 :fun Test()
 :py import vim