eval/environ: Prefer the last definition of an env var

It's possible for the environment variable block given to nvim to
contain multiple definitions for the same env var.  In this case, nvim
should preserve the last one defined.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 4486cd8f0d..7121d413ea 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1798,7 +1798,7 @@ static void f_environ(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   os_copy_fullenv(env, env_size);
 
-  for (size_t i = 0; i < env_size; i++) {
+  for (ssize_t i = env_size - 1; i >= 0; i--) {
     const char * str = env[i];
     const char * const end = strchr(str + (str[0] == '=' ? 1 : 0),
                                     '=');
@@ -1806,6 +1806,12 @@ static void f_environ(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     ptrdiff_t len = end - str;
     assert(len > 0);
     const char * value = str + len + 1;
+    if (tv_dict_find(rettv->vval.v_dict, str, len) != NULL) {
+      // Since we're traversing from the end of the env block to the front, any
+      // duplicate names encountered should be ignored.  This preserves the
+      // semantics of env vars defined later in the env block taking precedence.
+      continue;
+    }
     tv_dict_add_str(rettv->vval.v_dict,
                     str, len,
                     value);