Fix Issue 22738 - std.file.tempDir adds an addition / even when it al…

…ready has one

std/file.d

@@ -5274,7 +5274,21 @@ Returns:
 */
 string tempDir() @trusted
 {
-    import std.path : dirSeparator;
+    // We must check that the end of a path is not a seperator, before adding another
+    // If we don't we end up with https://issues.dlang.org/show_bug.cgi?id=22738
+    static string addSeperator(string input)
+    {
+        import std.path : dirSeparator;
+        import std.algorithm.searching : endsWith;
+
+        // It is very rare a directory path will reach this point with a directory seperator at the end
+        // However on OSX this can happen, so we must verify least we break user code i.e. https://github.com/dlang/dub/pull/2208
+        if (!input.endsWith(dirSeperator))
+            return input ~ dirSeperator;
+        else
+            return input;
+    }
+
     static string cache;
     if (cache is null)
     {
@@ -5294,7 +5308,7 @@ string tempDir() @trusted
             static string findExistingDir(T...)(lazy T alternatives)
             {
                 foreach (dir; alternatives)
-                    if (!dir.empty && exists(dir)) return dir ~ dirSeparator;
+                    if (!dir.empty && exists(dir)) return addSeperator(dir);
                 return null;
             }
 
@@ -5309,7 +5323,7 @@ string tempDir() @trusted
 
         if (cache is null)
         {
-            cache = getcwd() ~ dirSeparator;
+            cache = addSeperator(getcwd());
         }
     }
     return cache;
@@ -5338,6 +5352,9 @@ string tempDir() @trusted
     import std.algorithm.searching : endsWith;
     import std.path : dirSeparator;
     assert(tempDir.endsWith(dirSeparator));
+
+    // https://issues.dlang.org/show_bug.cgi?id=22738
+    assert(!tempDir.endsWith(dirSeparator ~ dirSeparator));
 }
 
 /**