From 6769438cd1392df684c7840ecb81335dc905c87d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Linse?= <bjorn.linse@gmail.com>
Date: Sat, 29 Aug 2015 16:11:56 +0200
Subject: [PATCH] encoding: don't allow changing encoding after startup scripts

---
 src/nvim/globals.h |  6 ++++++
 src/nvim/main.c    |  1 +
 src/nvim/option.c  | 13 ++++++++++---
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index e5a993aa5a..183e8fcff2 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -633,6 +633,10 @@ EXTERN int silent_mode INIT(= FALSE);
 /* set to TRUE when "-s" commandline argument
  * used for ex */
 
+// Set to true when sourcing of startup scripts (nvimrc) is done.
+// Used for options that cannot be changed after startup scripts.
+EXTERN bool did_source_startup_scripts INIT(= false);
+
 EXTERN pos_T VIsual;            /* start position of active Visual selection */
 EXTERN int VIsual_active INIT(= FALSE);
 /* whether Visual mode is active */
@@ -1078,6 +1082,8 @@ EXTERN garray_T error_ga
  * Excluded are errors that are only used once and debugging messages.
  */
 EXTERN char_u e_abort[] INIT(= N_("E470: Command aborted"));
+EXTERN char_u e_afterinit[] INIT(= N_(
+        "E905: Cannot set this option after startup"));
 EXTERN char_u e_api_spawn_failed[] INIT(= N_("E903: Could not spawn API job"));
 EXTERN char_u e_argreq[] INIT(= N_("E471: Argument required"));
 EXTERN char_u e_backslash[] INIT(= N_("E10: \\ should be followed by /, ? or &"));
diff --git a/src/nvim/main.c b/src/nvim/main.c
index dd2b813b1c..27f8340ec7 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1911,6 +1911,7 @@ static void source_startup_scripts(mparm_T *parmp)
       need_wait_return = TRUE;
     secure = 0;
   }
+  did_source_startup_scripts = true;
   TIME_MSG("sourcing vimrc file(s)");
 }
 
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 6e82c45edf..dba3bd8a26 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -575,6 +575,12 @@ void set_init_1(void)
     mb_init();
   }
 
+  // Don't change &encoding when resetting to defaults with ":set all&".
+  opt_idx = findoption((char_u *)"encoding");
+  if (opt_idx >= 0) {
+    options[opt_idx].flags |= P_NODEFAULT;
+  }
+
   /* Set the default for 'helplang'. */
   set_helplang_default(get_mess_lang());
 }
@@ -2271,10 +2277,11 @@ did_set_string_option (
   else if (varp == &p_ei) {
     if (check_ei() == FAIL)
       errmsg = e_invarg;
-  }
   /* 'encoding' and 'fileencoding' */
-  else if (varp == &p_enc || gvarp == &p_fenc) {
-    if (gvarp == &p_fenc) {
+  } else if (varp == &p_enc || gvarp == &p_fenc) {
+    if (varp == &p_enc && did_source_startup_scripts) {
+       errmsg = e_afterinit;
+    } else if (gvarp == &p_fenc) {
       if (!MODIFIABLE(curbuf) && opt_flags != OPT_GLOBAL)
         errmsg = e_modifiable;
       else if (vim_strchr(*varp, ',') != NULL)