From 0bcf96bf0bf1136aa4fb09dd86461312a2bc4fbb Mon Sep 17 00:00:00 2001
From: Gregory Anders <greg@gpanders.com>
Date: Thu, 10 Jun 2021 21:59:10 -0600
Subject: fix: source syncolors.vim before startup scripts

This fixes an issue (#12573) where colorscheme files are sourced twice
upon startup. This occurs when the startup script calls `:colorscheme`,
which sets the `g:colors_name` global variable. When syntax highlighting
is enabled in `syn_maybe_enable()` the `syntax.vim` script is sourced
which in turn sources `synload.vim`. This script checks to see if
`g:colors_name` is set and, if so, runs

    exe "colors " . colors_name

This is done to ensure that highlight groups are defined before enabling
the syntax highlighting engine.

Instead, source syncolors.vim before the startup scripts which sets up
default highlights and only load the full syntax engine after
the startup scripts or when the user runs `:syntax on`. Add a guard
variable `did_syncolor` to prevent syncolor.vim from being sourced
twice and remove the line mentioned above from synload.vim so that
the colorscheme file is not re-sourced when the syntax engine is loaded.
---
 runtime/syntax/syncolor.vim |  2 ++
 runtime/syntax/synload.vim  |  6 ++----
 src/nvim/main.c             | 12 ++++++++++--
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/runtime/syntax/syncolor.vim b/runtime/syntax/syncolor.vim
index 5b907a3b83..27cc3360c4 100644
--- a/runtime/syntax/syncolor.vim
+++ b/runtime/syntax/syncolor.vim
@@ -25,6 +25,8 @@ else
   endif
 endif
 
+let did_syncolor = 1
+
 " Many terminals can only use six different colors (plus black and white).
 " Therefore the number of colors used is kept low. It doesn't look nice with
 " too many colors anyway.
diff --git a/runtime/syntax/synload.vim b/runtime/syntax/synload.vim
index 3863a84c1a..aee9ba8b8e 100644
--- a/runtime/syntax/synload.vim
+++ b/runtime/syntax/synload.vim
@@ -14,10 +14,8 @@ endif
 " let others know that syntax has been switched on
 let syntax_on = 1
 
-" Set the default highlighting colors.  Use a color scheme if specified.
-if exists("colors_name")
-  exe "colors " . colors_name
-else
+" Set the default highlighting colors
+if !exists("colors_name") && !exists("did_syncolor")
   runtime! syntax/syncolor.vim
 endif
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 16700d20ab..621b93f9cc 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -367,11 +367,19 @@ int main(int argc, char **argv)
   // Execute --cmd arguments.
   exe_pre_commands(&params);
 
+  // If using the runtime (-u is not NONE), enable syntax & filetype plugins.
+  bool enable_syntax =
+    (params.use_vimrc == NULL || !strequal(params.use_vimrc, "NONE"));
+
+  // Source syncolor.vim to set up default UI highlights
+  if (enable_syntax) {
+    source_runtime((char_u *)"syntax/syncolor.vim", DIP_ALL);
+  }
+
   // Source startup scripts.
   source_startup_scripts(&params);
 
-  // If using the runtime (-u is not NONE), enable syntax & filetype plugins.
-  if (params.use_vimrc == NULL || !strequal(params.use_vimrc, "NONE")) {
+  if (enable_syntax) {
     // Does ":filetype plugin indent on".
     filetype_maybe_enable();
     // Sources syntax/syntax.vim, which calls `:filetype on`.
-- 
cgit