The decision by French President Emmanuel Macron to call a snap election after losing to the far right in a vote for European lawmakers roiled markets and the euro Monday. Big gains for the far right in the French election could force Macron to govern with a hostile parliament, making it harder for his centrist administration to pursue its policy agenda and raising doubts about its ability to put government finances on a more sustainable footing. France’s CAC 40 index, which represents 40...