Clean up @test_*_tmp artifacts after each test run

Author: mikasoukhov

tests/IronPython.Tests/Cases/CommonCases.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.IO;
 using System.Threading;
 
 using NUnit.Framework;
@@ -36,6 +37,42 @@ protected int TestImpl(TestInfo testcase) {
                 return -1;
             } finally {
                 m?.ReleaseMutex();
+                CleanupTempFiles(testcase);
+            }
+        }
+
+        /// <summary>
+        /// Removes @test_*_tmp files/directories left behind by test.support.TESTFN.
+        /// </summary>
+        private static void CleanupTempFiles(TestInfo testcase) {
+            var testDir = Path.GetDirectoryName(testcase.Path);
+            if (testDir is null) return;
+
+            // Clean test directory and also the StdLib test directory
+            CleanupTempFilesInDir(testDir);
+            var stdlibTestDir = Path.Combine(CaseExecuter.FindRoot(), "src", "core", "IronPython.StdLib", "lib", "test");
+            if (stdlibTestDir != testDir) {
+                CleanupTempFilesInDir(stdlibTestDir);
+            }
+        }
+
+        private static void CleanupTempFilesInDir(string dir) {
+            if (!Directory.Exists(dir)) return;
+
+            try {
+                foreach (var entry in Directory.EnumerateFileSystemEntries(dir, "@test_*_tmp*")) {
+                    try {
+                        if (File.GetAttributes(entry).HasFlag(FileAttributes.Directory)) {
+                            Directory.Delete(entry, recursive: true);
+                        } else {
+                            File.Delete(entry);
+                        }
+                    } catch {
+                        // ignore locked/in-use files
+                    }
+                }
+            } catch {
+                // ignore enumeration errors
             }
         }
     }