3 files changed, 44 insertions, 1 deletions
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index 21f0fc6f41..2e671653ed 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -146,6 +146,16 @@ static bool is_executable_in_path(const char_u *name, char_u **abspath)
   }
 
   size_t buf_len = STRLEN(name) + STRLEN(path) + 2;
+
+#ifdef WIN32
+  const char *pathext = os_getenv("PATHEXT");
+  if (!pathext) {
+    pathext = ".com;.exe;.bat;.cmd";
+  }
+
+  buf_len += STRLEN(pathext);
+#endif
+
   char_u *buf = xmalloc(buf_len);
 
   // Walk through all entries in $PATH to check if "name" exists there and
@@ -169,6 +179,38 @@ static bool is_executable_in_path(const char_u *name, char_u **abspath)
       return true;
     }
 
+#ifdef WIN32
+    // Try appending file extensions from $PATHEXT to the name.
+    char *buf_end = xstrchrnul((char *)buf, '\0');
+    for (const char *ext = pathext; *ext; ext++) {
+      // Skip the extension if there is no suffix after a '.'.
+      if (ext[0] == '.' && (ext[1] == '\0' || ext[1] == ';')) {
+        *ext++;
+
+        continue;
+      }
+
+      const char *ext_end = xstrchrnul(ext, ENV_SEPCHAR);
+      STRLCPY(buf_end, ext, ext_end - ext + 1);
+
+      if (is_executable(buf)) {
+        // Check if the caller asked for a copy of the path.
+        if (abspath != NULL) {
+          *abspath = save_absolute_path(buf);
+        }
+
+        xfree(buf);
+
+        return true;
+      }
+
+      if (*ext_end != ENV_SEPCHAR) {
+        break;
+      }
+      ext = ext_end;
+    }
+#endif
+
     if (*e != ENV_SEPCHAR) {
       // End of $PATH without finding any executable called name.
       xfree(buf);
diff --git a/src/nvim/os/unix_defs.h b/src/nvim/os/unix_defs.h
index 78fc9331d1..690a39c3cd 100644
--- a/src/nvim/os/unix_defs.h
+++ b/src/nvim/os/unix_defs.h
@@ -2,7 +2,7 @@
 #define NVIM_OS_UNIX_DEFS_H
 
 // Windows doesn't have unistd.h, so we include it here to avoid numerous
-// instances of `#ifdef HAVE_UNISTD_H'.
+// instances of `#ifdef WIN32'.
 #include <unistd.h>
 
 // POSIX.1-2008 says that NAME_MAX should be in here
diff --git a/src/nvim/os/win_defs.h b/src/nvim/os/win_defs.h
index ba96347a12..242d355f77 100644
--- a/src/nvim/os/win_defs.h
+++ b/src/nvim/os/win_defs.h
@@ -3,6 +3,7 @@
 
 #include <windows.h>
 #include <sys/stat.h>
+#include <io.h>
 #include <stdio.h>
 
 // Windows does not have S_IFLNK but libuv defines it