From d250905c69c0a8d2ac99c4ade9cfb574a011faaf Mon Sep 17 00:00:00 2001
From: James McCoy <jamessan@jamessan.com>
Date: Thu, 13 May 2021 20:56:25 -0400
Subject: [PATCH 1/2] test(job_spec): Test handling of case-insensitively
 matching env vars

Since Windows is case-insensitive, there should only be a single env var
in visible in the resulting job.  However, non-Windows should see both.
---
 test/functional/core/job_spec.lua | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/test/functional/core/job_spec.lua b/test/functional/core/job_spec.lua
index 9de0d08e79..34ab90d760 100644
--- a/test/functional/core/job_spec.lua
+++ b/test/functional/core/job_spec.lua
@@ -118,6 +118,32 @@ describe('jobs', function()
     end
   end)
 
+  it('handles case-insensitively matching #env vars', function()
+    nvim('command', "let $TOTO = 'abc'")
+    -- Since $Toto is being set in the job, it should take precedence over the
+    -- global $TOTO on Windows
+    nvim('command', "let g:job_opts = {'env': {'Toto': 'def'}, 'stdout_buffered': v:true}")
+    if iswin() then
+      nvim('command', [[let j = jobstart('set | find /I "toto="', g:job_opts)]])
+    else
+      nvim('command', [[let j = jobstart('env | grep -i toto=', g:job_opts)]])
+    end
+    nvim('command', "call jobwait([j])")
+    nvim('command', "let g:output = Normalize(g:job_opts.stdout)")
+    local actual = eval('g:output')
+    local expected
+    if iswin() then
+      -- Toto is normalized to TOTO so we can detect duplicates, and because
+      -- Windows doesn't care about case
+      expected = {'TOTO=def', ''}
+    else
+      expected = {'TOTO=abc', 'Toto=def', ''}
+    end
+    table.sort(actual)
+    table.sort(expected)
+    eq(expected, actual)
+  end)
+
   it('uses &shell and &shellcmdflag if passed a string', function()
     nvim('command', "let $VAR = 'abc'")
     if iswin() then

From 88ee095d42e222ec2353b1eaae48a2a9a65b1d9d Mon Sep 17 00:00:00 2001
From: James McCoy <jamessan@jamessan.com>
Date: Tue, 18 May 2021 06:54:24 -0400
Subject: [PATCH 2/2] fix(job): Deduplicate env var names on Windows

Windows handles environment variable names case-insensitively (i.e.,
%Path% can be accessed via %PATH%).  Since nvim explicitly creates the
environment block for jobs, we need to ensure it doesn't contain
duplicate names with different cases (e.g., both %Path% and %PATH%) as
that can confuse processes using the environment.

`f_environ()` now converts all env var names to upper-case on Windows,
since it does duplicate detection and also provides the base environment
for jobs.  Similarly, `create_environment()` converts any env var names
supplied in the job opts to upper-case so they can be compared against
what we get from `f_environ()`.

Closes #14541
---
 src/nvim/eval/funcs.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 072d206ecb..caaf675db2 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1850,15 +1850,30 @@ 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) {
+
+    char c = env[i][len];
+    env[i][len] = NUL;
+
+#ifdef WIN32
+    // Upper-case all the keys for Windows so we can detect duplicates
+    char *const key = strcase_save(str, true);
+#else
+    char *const key = xstrdup(str);
+#endif
+
+    env[i][len] = c;
+
+    if (tv_dict_find(rettv->vval.v_dict, key, 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.
+      xfree(key);
       continue;
     }
     tv_dict_add_str(rettv->vval.v_dict,
-                    str, len,
+                    key, len,
                     value);
+    xfree(key);
   }
   os_free_fullenv(env);
 }
@@ -5096,7 +5111,21 @@ static dict_T *create_environment(const dictitem_T *job_env,
   }
 
   if (job_env) {
+#ifdef WIN32
+    TV_DICT_ITER(job_env->di_tv.vval.v_dict, var, {
+      // Always use upper-case keys for Windows so we detect duplicate keys
+      char *const key = strcase_save((const char *)var->di_key, true);
+      size_t len = strlen(key);
+      dictitem_T *dv = tv_dict_find(env, key, len);
+      if (dv) {
+        tv_dict_item_remove(env, dv);
+      }
+      tv_dict_add_str(env, key, len, tv_get_string(&var->di_tv));
+      xfree(key);
+    });
+#else
     tv_dict_extend(env, job_env->di_tv.vval.v_dict, "force");
+#endif
   }
 
   if (pty) {