1 files changed, 60 insertions, 1 deletions
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 747a34d8ce..5a3c1ef2c8 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -9,6 +9,7 @@
 #include "nvim/vim.h"
 #include "nvim/ascii.h"
 #include "nvim/charset.h"
+#include "nvim/fileio.h"
 #include "nvim/os/os.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
@@ -18,6 +19,10 @@
 #include "nvim/ex_getln.h"
 #include "nvim/version.h"
 
+#ifdef WIN32
+#include "nvim/mbyte.h"  // for utf8_to_utf16, utf16_to_utf8
+#endif
+
 #ifdef HAVE__NSGETENVIRON
 #include <crt_externs.h>
 #endif
@@ -45,7 +50,21 @@ bool os_env_exists(const char *name)
 int os_setenv(const char *name, const char *value, int overwrite)
   FUNC_ATTR_NONNULL_ALL
 {
-#ifdef HAVE_SETENV
+#ifdef WIN32
+  size_t envbuflen = strlen(name) + strlen(value) + 2;
+  char *envbuf = xmalloc(envbuflen);
+  snprintf(envbuf, envbuflen, "%s=%s", name, value);
+
+  WCHAR *p;
+  utf8_to_utf16(envbuf, &p);
+  xfree(envbuf);
+  if (p == NULL) {
+    return -1;
+  }
+  _wputenv(p);
+  xfree(p);  // Unlike Unix systems, we can free the string for _wputenv().
+  return 0;
+#elif defined(HAVE_SETENV)
   return setenv(name, value, overwrite);
 #elif defined(HAVE_PUTENV_S)
   if (!overwrite && os_getenv(name) != NULL) {
@@ -831,3 +850,43 @@ char_u *get_env_name(expand_T *xp, int idx)
   return NULL;
 }
 
+/// Appends the head of `fname` to $PATH and sets it in the environment.
+///
+/// @param fname  Full path whose parent directory will be appended to $PATH.
+///
+/// @return true if `path` was appended-to
+bool os_setenv_append_path(const char *fname)
+  FUNC_ATTR_NONNULL_ALL
+{
+#ifdef WIN32
+// 8191 (plus NUL) is considered the practical maximum.
+# define MAX_ENVPATHLEN 8192
+#else
+// No prescribed maximum on unix.
+# define MAX_ENVPATHLEN INT_MAX
+#endif
+  if (!path_is_absolute_path((char_u *)fname)) {
+    EMSG2(_(e_intern2), "os_setenv_append_path()");
+    return false;
+  }
+  const char *tail = (char *)path_tail_with_sep((char_u *)fname);
+  const char *dir = (char *)vim_strnsave((char_u *)fname,
+                                         (size_t)(tail - fname));
+  const char *path = os_getenv("PATH");
+  const size_t pathlen = path ? strlen(path) : 0;
+  const size_t newlen = pathlen + strlen(dir) + 2;
+  if (newlen < MAX_ENVPATHLEN) {
+    char *temp = xmalloc(newlen);
+    if (pathlen == 0) {
+      temp[0] = NUL;
+    } else {
+      xstrlcpy(temp, path, newlen);
+      xstrlcat(temp, ENV_SEPSTR, newlen);
+    }
+    xstrlcat(temp, dir, newlen);
+    os_setenv("PATH", temp, 1);
+    xfree(temp);
+    return true;
+  }
+  return false;
+}