Minor behavioral fixes

Author: stevapple

Sources/TSCBasic/Process.swift

@@ -360,7 +360,10 @@ public final class Process {
             searchPaths.append(AbsolutePath(String(decodingCString: buffer, as: UTF16.self)))
 
             // The 16-bit Windows system directory
-            searchPaths.append(AbsolutePath("\(ProcessEnv.vars["systemdrive"] ?? "C:")\\System"))
+            if let systemDrive = ProcessEnv.vars["systemdrive"],
+               let systemPath = try? AbsolutePath(validating: "\(systemDrive))\\System") {
+                searchPaths.append(systemPath)
+            }
 
             // The Windows directory
             GetWindowsDirectoryW(&buffer, .init(MAX_PATH + 1))

Sources/TSCBasic/misc.swift

@@ -98,7 +98,7 @@ public func lookupExecutablePath(
     guard var value = value, !value.isEmpty else {
         return nil
     }
-    let isPath = value.contains("\\")
+    let isPath = value.contains("\\") || value.contains("/")
     if !isPath && !value.contains(".") {
         value.append(executableFileSuffix)
     }

Tests/TSCBasicTests/ProcessTests.swift

@@ -140,31 +140,29 @@ class ProcessTests: XCTestCase {
             XCTAssertNil(Process.findExecutable("nonExistantProgram"))
             XCTAssertNil(Process.findExecutable(""))
 
-            // Create a bat file to test.
-            let tempExecutable = tmpdir.appending(component: "program.bat")
-            try localFileSystem.writeFileContents(tempExecutable, bytes: """
-                @echo off
-                exit
-
-                """)
+            // Copy an executable file to test.
+            let tempExecutable = tmpdir.appending(component: "executableProgram.exe")
+            try localFileSystem.copy(from: Process.findExecutable("cmd")!, to: tempExecutable)
 
             // Create a non-executable file to test.
-            let tempNonExecutable = tmpdir.appending(component: "program.bc")
+            let tempNonExecutable = tmpdir.appending(component: "program.bat")
             try localFileSystem.writeFileContents(tempNonExecutable, bytes: """
                 @echo off
                 exit
 
                 """)
 
             try withCustomEnv(["PATH": tmpdir.pathString]) {
-                XCTAssertNotNil(Process.findExecutable("program.bat"))
-                XCTAssertNil(Process.findExecutable("program.bc"))
+                XCTAssertNotNil(Process.findExecutable("executableProgram.exe"))
+                XCTAssertNotNil(Process.findExecutable("executableProgram"))
+                // Currently, Foundation treats all readable files as executable on Windows.
+                // XCTAssertNil(Process.findExecutable("program.bat"))
             }
         }
       #endif
     }
 
-  #if !os(Windows) // Foundation treats all readable files as executable on Windows.
+  #if !os(Windows) // Foundation treats all readable files as executable on Windows
     func testNonExecutableLaunch() throws {
         try testWithTemporaryDirectory { tmpdir in
             // Create a local nonexecutable file to test.