From 207ba359b0127fa5893b980abcb9186ffec1879c Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Wed, 11 Jan 2017 06:00:55 +0100
Subject: [PATCH] Windows: vim_getenv(): Find runtime relative to nvim. #3303
 (#5929)

In Windows we cannot rely on absolute install paths to point to the
location of the runtime. Vim uses the path of the current binary as
a possible location for the runtime folder. In Neovim the install
location places the runtime folder in ../share/nvim/runtime.

In Vim this logic is guarded by USE_EXE_NAME, which is defined for win32
and macOS.

TODO: We may need to incorporate similar logic for macOS:
https://github.com/vim/vim/blob/0cdb72aa38c4a0140c94d56bf8bc17cb30260ebf/src/misc1.c#L4287-L4308
---
 src/nvim/os/env.c | 25 +++++++++++++++++++++++--
 src/nvim/os/fs.c  | 12 ++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 83a0262545..47d541c6a7 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -560,8 +560,8 @@ const void *vim_colon_env_iter_rev(const char *const val,
 /// Vim's version of getenv().
 /// Special handling of $HOME, $VIM and $VIMRUNTIME, allowing the user to
 /// override the vim runtime directory at runtime.  Also does ACP to 'enc'
-/// conversion for Win32.  Results must be freed by the calling function.
-/// @param name Name of environment variable to expand
+/// conversion for Win32.  Result must be freed by the caller.
+/// @param name Environment variable to expand
 char *vim_getenv(const char *name)
 {
   const char *kos_env_path = os_getenv(name);
@@ -598,6 +598,27 @@ char *vim_getenv(const char *name)
     if (p_hf != NULL && vim_strchr(p_hf, '$') == NULL) {
       vim_path = (char *)p_hf;
     }
+
+#ifdef WIN32
+    // Find runtime path relative to the nvim binary i.e. ../share/runtime
+    if (vim_path == NULL) {
+      char exe_name[MAXPATHL];
+      size_t exe_name_len = MAXPATHL;
+      if (os_exepath(exe_name, &exe_name_len) == 0) {
+        char *path_end = (char *)path_tail_with_sep((char_u *)exe_name);
+        *path_end = '\0';  // remove the trailing "nvim.exe"
+        path_end = (char *)path_tail((char_u *)exe_name);
+        *path_end = '\0';  // remove the trailing "bin/"
+        if (append_path(
+            exe_name,
+            "share" _PATHSEPSTR "nvim" _PATHSEPSTR "runtime" _PATHSEPSTR,
+            MAXPATHL) == OK) {
+          vim_path = exe_name;
+        }
+      }
+    }
+#endif
+
     if (vim_path != NULL) {
       // remove the file name
       char *vim_path_end = (char *)path_tail((char_u *)vim_path);
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index 3c821936e9..4aa727733e 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -192,6 +192,18 @@ int os_nodetype(const char *name)
   return nodetype;
 }
 
+/// Gets the absolute path of the currently running executable.
+///
+/// @param[out] buffer Returns the path string.
+/// @param[in]  size   Size of `buffer`.
+///
+/// @return `0` on success, or libuv error code on failure.
+int os_exepath(char *buffer, size_t *size)
+  FUNC_ATTR_NONNULL_ALL
+{
+  return uv_exepath(buffer, size);
+}
+
 /// Checks if the given path represents an executable file.
 ///
 /// @param[in]  name     Name of the executable.