src/plugins/webpackHotDevClient.js
function handleWarnings(warnings) {
  clearOutdatedErrors();
  destroyErrorOverlay();

  var isHotUpdate = !isFirstCompilation;
  isFirstCompilation = false;
  hasCompileErrors = false;

  function printWarnings() {
    // Print warnings to the console.
    for (var i = 0; i < warnings.length; i++) {
      console.warn(stripAnsi(warnings[i]));
    }
  }

  // Attempt to apply hot updates or reload.
  if (isHotUpdate) {
    tryApplyUpdates(function onSuccessfulHotUpdate() {
      // Only print warnings if we aren't refreshing the page.
      // Otherwise they'll disappear right away anyway.
      printWarnings();
    });
  } else {
    // Print initial warnings immediately.
    printWarnings();
  }
}
function handleWarnings(warnings) {
  clearOutdatedErrors();
  destroyErrorOverlay();

  var isHotUpdate = !isFirstCompilation;
  isFirstCompilation = false;
  hasCompileErrors = false;

  function printWarnings() {
    // Print warnings to the console.
    for (var i = 0; i < warnings.length; i++) {
      console.warn(stripAnsi(warnings[i]));
    }
  }

  // Attempt to apply hot updates or reload.
  if (isHotUpdate) {
    tryApplyUpdates(function onSuccessfulHotUpdate() {
      // Only print warnings if we aren't refreshing the page.
      // Otherwise they'll disappear right away anyway.
      printWarnings();
    });
  } else {
    // Print initial warnings immediately.
    printWarnings();
  }
}
Compilation with warnings (e.g. ESLint).