testdriver: fix data race introduced in #1101

With #1101 a data race was accidentally introduced where the global
testsetup.VimCommand was overwritten.
We now make a local copy that is modified instead.

Fixing this revealed that #1101 wasn't enough. Testscript conditions
that matches a vim version also used the testscript subcommand instead
of real vim. It now uses the real vim.

Closes #1104

testdriver/testdriver.go

@@ -196,7 +196,8 @@ func NewTestDriver(c *Config) (*TestDriver, error) {
 		"GOVIMTESTDRIVER_SOCKET="+res.driverListener.Addr().String(),
 	)
 
-	vimCmd := cmd
+	vimCmd := make([]string, len(cmd))
+	copy(vimCmd, cmd)
 	if e := os.Getenv("VIM_COMMAND"); e != "" {
 		vimCmd = strings.Fields(e)
 	}
@@ -249,6 +250,7 @@ func NewTestDriver(c *Config) (*TestDriver, error) {
 func (d *TestDriver) Logf(format string, a ...interface{}) {
 	fmt.Fprintf(d.log, format+"\n", a...)
 }
+
 func (d *TestDriver) LogStripANSI(r io.Reader) {
 	scanner := bufio.NewScanner(r)
 	for {
@@ -588,7 +590,6 @@ func (d *TestDriver) listenDriver() error {
 		}
 		return nil
 	})
-
 	if err != nil {
 		return fmt.Errorf("%v", err)
 	}
@@ -933,8 +934,22 @@ func Condition(cond string) (bool, error) {
 }
 
 func getVimFlavourVersion(c testsetup.Command) (string, error) {
-	var allArgs []string
-	allArgs = append(allArgs, c...)
+	allArgs := make([]string, len(c))
+	// testscript prepends PATH with the directory that contain
+	// subcommands. Since we are going to execute vim here, and also
+	// also have a subcommand named "vim", we must specify the entire path if
+	// "vim" is a part of c.
+	for i := range c {
+		if c[i] != "vim" {
+			allArgs[i] = c[i]
+			continue
+		}
+		abs, err := testsetup.RealVimPath()
+		if err != nil {
+			return "", fmt.Errorf("failed to find vim binary: %v", err)
+		}
+		allArgs[i] = abs
+	}
 	allArgs = append(allArgs, "-v", "--cmd", "echo v:versionlong | qall", "--not-a-term")
 	cmd := exec.Command(allArgs[0], allArgs[1:]...)
 	out, err := cmd.CombinedOutput()

testsetup/testsetup.go

@@ -161,8 +161,10 @@ func EnvLookupFlavorCommand() (flav govim.Flavor, cmd Command, err error) {
 // executable found. Reason being that testscript prepends
 // the PATH with the subcommand dir causing a conflict where
 // the first vim found is the subcommand.
+// If there is only one vim executable it will be returned
+// as fallback.
 func RealVimPath() (path string, err error) {
-	var firstFound bool
+	var firstFound string
 	for _, dir := range filepath.SplitList(os.Getenv("PATH")) {
 		path := filepath.Join(dir, "vim")
 		d, err := os.Stat(path)
@@ -172,10 +174,14 @@ func RealVimPath() (path string, err error) {
 		if m := d.Mode(); m.IsDir() || m&0111 == 0 {
 			continue
 		}
-		if firstFound {
+		if firstFound != "" {
 			return path, nil
 		}
-		firstFound = true
+		firstFound = path
+	}
+	if firstFound != "" {
+		// fallback
+		return firstFound, nil
 	}
 	return "", fmt.Errorf("not found")
 }