The U.S. Supreme Court has just denied the petition from the state of Texas for leave to file a complaint against the state of Wisconsin.
Ten months ago they denied a petition from the state of Arizona for leave to file a complaint against the state of California.
In both cases, Justices Thomas and Alito said they do not have discretionary power to deny such leave because the Constitution says that when one of the states sues another, the U.S. Supreme Court "shall", not "may", have jurisdiction.
Why does this question arise? Why can't a state just file a complaint that the justices can decide to toss out, or not, as they judge fit, instead of first requesting leave to file a complaint. Suppose a state did just that. What would the Court do?