Moved helper functions into non-test code for reuse elsewhere

cli/helper.go

@@ -0,0 +1,64 @@
+package cli
+
+import (
+	"bytes"
+	"io"
+	"os"
+)
+
+// RunWithArgs executes the given command with the specified command line args
+// and environmental variables set. It returns any error returned from cmd.Execute()
+func RunWithArgs(cmd Executable, args []string, env map[string]string) error {
+	oargs := os.Args
+	oenv := map[string]string{}
+	// defer returns the environment back to normal
+	defer func() {
+		os.Args = oargs
+		for k, v := range oenv {
+			os.Setenv(k, v)
+		}
+	}()
+
+	// set the args and env how we want them
+	os.Args = args
+	for k, v := range env {
+		// backup old value if there, to restore at end
+		oenv[k] = os.Getenv(k)
+		err := os.Setenv(k, v)
+		if err != nil {
+			return err
+		}
+	}
+
+	// and finally run the command
+	return cmd.Execute()
+}
+
+// RunCaptureWithArgs executes the given command with the specified command line args
+// and environmental variables set. It returns whatever was writen to
+// stdout along with any error returned from cmd.Execute()
+func RunCaptureWithArgs(cmd Executable, args []string, env map[string]string) (output string, err error) {
+	old := os.Stdout // keep backup of the real stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+	defer func() {
+		os.Stdout = old // restoring the real stdout
+	}()
+
+	outC := make(chan string)
+	// copy the output in a separate goroutine so printing can't block indefinitely
+	go func() {
+		var buf bytes.Buffer
+		// io.Copy will end when we call w.Close() below
+		io.Copy(&buf, r)
+		outC <- buf.String()
+	}()
+
+	// now run the command
+	err = RunWithArgs(cmd, args, env)
+
+	// and grab the stdout to return
+	w.Close()
+	output = <-outC
+	return output, err
+}