Fixed gulpfile for version 4

Signed-off-by: Jim Martens <github@2martens.de>

gulpfile.js

@@ -51,7 +51,7 @@ gulp.task("build:styles:critical", function() {
 });
 
 // Builds all styles.
-gulp.task("build:styles", ["build:styles:main", "build:styles:critical"]);
+gulp.task("build:styles", gulp.series("build:styles:main", "build:styles:critical"));
 
 gulp.task("clean:styles", function (callback) {
     del([paths.jekyllCssFiles + "main.css",
@@ -101,7 +101,7 @@ gulp.task("clean:scripts:leaflet", function(callback) {
 });
 
 // Builds all scripts.
-gulp.task("build:scripts", ["build:scripts:global", "build:scripts:leaflet"]);
+gulp.task("build:scripts", gulp.series("build:scripts:global", "build:scripts:leaflet"));
 
 // Optimizes and copies image files.
 gulp.task("build:images", function () {
@@ -150,53 +150,53 @@ gulp.task("clean:jekyll", function(callback) {
     callback();
 });
 
-gulp.task("clean", ["clean:jekyll",
+gulp.task("clean", gulp.series("clean:jekyll",
     "clean:images",
     "clean:scripts",
-    "clean:styles"]);
+    "clean:styles"));
 
 // Builds site anew.
 gulp.task("build", function (callback) {
-    runSequence("clean",
-        ["build:scripts", "build:images", "build:styles"],
-        "build:jekyll",
-        callback);
+    gulp.series("clean",
+        gulp.series("build:scripts", "build:images", "build:styles"),
+        "build:jekyll");
+    callback();
 });
 
 // Builds site anew using test config.
 gulp.task("build:test", function (callback) {
-    runSequence("clean",
-        ["build:scripts", "build:images", "build:styles"],
-        "build:jekyll:test",
-        callback);
+    gulp.series("clean",
+        gulp.series("build:scripts", "build:images", "build:styles"),
+        "build:jekyll:test");
+    callback();
 });
 
 // Builds site anew using local config.
 gulp.task("build:local", function (callback) {
-    runSequence("clean",
-        ["build:scripts", "build:images", "build:styles"],
-        "build:jekyll:local",
-        callback);
+    gulp.series("clean",
+        gulp.series("build:scripts", "build:images", "build:styles"),
+        "build:jekyll:local");
+    callback();
 });
 
 // Default Task: builds site.
-gulp.task("default", ["build"]);
+gulp.task("default", gulp.series("build"));
 
 // Special tasks for building and then reloading BrowserSync.
-gulp.task("build:jekyll:watch", ["build:jekyll:local"], function(callback) {
+gulp.task("build:jekyll:watch", gulp.series("build:jekyll:local", function (callback) {
     browserSync.reload();
     callback();
-});
+}));
 
-gulp.task("build:scripts:watch", ["build:scripts"], function(callback) {
+gulp.task("build:scripts:watch", gulp.series("build:scripts", function (callback) {
     browserSync.reload();
     callback();
-});
+}));
 
 // Static Server + watching files.
 // Note: passing anything besides hard-coded literal paths with globs doesn't
 // seem to work with gulp.watch().
-gulp.task("serve", ["build:local"], function() {
+gulp.task("serve", gulp.series("build:local", function () {
 
     browserSync.init({
         server: paths.siteDir,
@@ -207,37 +207,37 @@ gulp.task("serve", ["build:local"], function() {
     });
 
     // Watch site settings.
-    gulp.watch(["_config.yml"], ["build:jekyll:watch"]);
+    gulp.watch(["_config.yml"], gulp.series("build:jekyll:watch"));
 
     // Watch .scss files; changes are piped to browserSync.
-    gulp.watch("_assets/styles/**/*.scss", ["build:styles"]);
+    gulp.watch("_assets/styles/**/*.scss", gulp.series("build:styles"));
 
     // Watch .js files.
-    gulp.watch("_assets/js/**/*.js", ["build:scripts:watch"]);
+    gulp.watch("_assets/js/**/*.js", gulp.series("build:scripts:watch"));
 
     // Watch image files; changes are piped to browserSync.
-    gulp.watch("_assets/img/**/*", ["build:images"]);
+    gulp.watch("_assets/img/**/*", gulp.series("build:images"));
 
     // Watch posts.
-    gulp.watch("_posts/**/*.+(md|markdown|MD)", ["build:jekyll:watch"]);
+    gulp.watch("_posts/**/*.+(md|markdown|MD)", gulp.series("build:jekyll:watch"));
 
     // Watch drafts if --drafts flag was passed.
     if (module.exports.drafts) {
-        gulp.watch("_drafts/*.+(md|markdown|MD)", ["build:jekyll:watch"]);
+        gulp.watch("_drafts/*.+(md|markdown|MD)", gulp.series("build:jekyll:watch"));
     }
 
     // Watch html and markdown files.
-    gulp.watch(["**/*.+(html|md|markdown|MD)", "!_site/**/*.*"], ["build:jekyll:watch"]);
+    gulp.watch(["**/*.+(html|md|markdown|MD)", "!_site/**/*.*"], gulp.series("build:jekyll:watch"));
 
     // Watch RSS feed XML files.
-    gulp.watch("**.xml", ["build:jekyll:watch"]);
+    gulp.watch("**.xml", gulp.series("build:jekyll:watch"));
 
     // Watch data files.
-    gulp.watch("_data/**.*+(yml|yaml|csv|json)", ["build:jekyll:watch"]);
+    gulp.watch("_data/**.*+(yml|yaml|csv|json)", gulp.series("build:jekyll:watch"));
 
     // Watch favicon.png.
-    gulp.watch("favicon.png", ["build:jekyll:watch"]);
-});
+    gulp.watch("favicon.png", gulp.series("build:jekyll:watch"));
+}));
 
 // Updates Ruby gems
 gulp.task("update:bundle", function () {