Fixes microsoft#558 Crash when uninstalling Python

Handles IOException and retries getting subkeys if we race with external registry edits. Adds test.
clarartp · Jul 9, 2015 · d9bf776 · d9bf776
1 parent 586d9ac
commit d9bf776
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Showing 2 changed files with 33 additions and 1 deletion.
diff --git a/Python/Product/VSInterpreters/CPythonInterpreterFactoryProvider.cs b/Python/Product/VSInterpreters/CPythonInterpreterFactoryProvider.cs
@@ -19,6 +19,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Text.RegularExpressions;
+using System.Threading;
 using Microsoft.PythonTools.Analysis;
 using Microsoft.VisualStudioTools;
 using Microsoft.Win32;
@@ -143,7 +144,23 @@ private static bool TryParsePythonVersion(string spec, out Version version, out
         private bool RegisterInterpreters(HashSet<string> registeredPaths, RegistryKey python, ProcessorArchitecture? arch) {
             bool anyAdded = false;
 
-            foreach (var key in python.GetSubKeyNames()) {
+            string[] subKeyNames = null;
+            for (int retries = 5; subKeyNames == null && retries > 0; --retries) {
+                try {
+                    subKeyNames = python.GetSubKeyNames();
+                } catch (IOException) {
+                    // Registry changed while enumerating subkeys. Give it a
+                    // short period to settle down and try again.
+                    // We are almost certainly being called from a background
+                    // thread, so sleeping here is fine.
+                    Thread.Sleep(100);
+                }
+            }
+            if (subKeyNames == null) {
+                return false;
+            }
+
+            foreach (var key in subKeyNames) {
                 Version version;
                 ProcessorArchitecture? arch2;
                 if (TryParsePythonVersion(key, out version, out arch2)) {

diff --git a/Python/Tests/Core/CPythonInterpreterTests.cs b/Python/Tests/Core/CPythonInterpreterTests.cs
@@ -16,6 +16,7 @@
 using System.Linq;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.Win32;
 using TestUtilities;
 using TestUtilities.Python;
 
@@ -49,5 +50,19 @@ public void FactoryProvider() {
                 }
             }
         }
+
+        [TestMethod, Priority(0)]
+        public void DiscoverRegistryRace() {
+            // https://github.com/Microsoft/PTVS/issues/558
+
+            using (var key = Registry.CurrentUser.CreateSubKey(@"Software\Python\PythonCore", true)) {
+                for (int changes = 0; changes < 1000; ++changes) {
+                    // Doesn't matter about the name - we just want to trigger
+                    // discovery and then remove the key during GetSubKeyNames.
+                    key.CreateSubKey("NotARealInterpreter").Close();
+                    key.DeleteSubKey("NotARealInterpreter", false);
+                }
+            }
+        }
     }
 }