Bug 575159: Consider return code of wsl.exe

If the return code is non-zero wsl may have failed in someway, with
recent changes in Windows, wsl.exe is present even when wsl is not
installed. In that case wsl.exe is a dummy that can be used to install
wsl.

Change-Id: I83af60623084e1364d16c3a1739bc4f6a25ac3a9

terminal/plugins/org.eclipse.tm.terminal.view.ui/src/org/eclipse/tm/terminal/view/ui/local/showin/detectors/DetectWSL.java

@@ -144,6 +144,18 @@ public class DetectWSL implements IDetectExternalExecutable {
 						}
 					}
 
+					try {
+						// lets get the return code to make sure that the process did not produce anything unexpected. As the streams
+						// are closed, the waitFor shouldn't block.
+						if (process.waitFor() != 0) {
+							// WSL can send errors to stdout, so discard results if the exit value ends up being non-zero
+							result.clear();
+						}
+					} catch (InterruptedException e) {
+						// we've been interrupted, give up on the output we have (probably unreachable in practice)
+						result.clear();
+					}
+
 				} catch (IOException e) {
 				}
 			}