fix: move version output from preversion to version script (#546)

gulpfile.js

@@ -106,18 +106,14 @@ function polymerBuild() {
 }
 
 gulp.task('version:update', function() {
-  // Should be run from 'preversion'
-  // Assumes that the old version is in package.json and the new version in the `npm_package_version` environment variable
-  const oldversion = require('./package.json').version;
+  // Should be run from 'version'
+  // Assumes that the new version is in the `npm_package_version` environment variable
   const newversion = process.env.npm_package_version;
-  if (!oldversion) {
-    throw new 'No old version found in package.json';
-  }
   if (!newversion) {
     throw new 'New version must be given as a npm_package_version environment variable.';
   }
   return gulp.src(['src/router-meta.js'])
-    .pipe(replace(oldversion, newversion))
+    .pipe(replace(/version: '.*'/, `version: '${newversion}'`))
     .pipe(gulp.dest('src'))
     .pipe(git.add());
 });

package.json

@@ -46,7 +46,7 @@
     "docs:analyze": "polymer analyze dist/vaadin-router.js src/documentation/*.js > analysis.json",
     "browserslist": "browserslist && browserslist --coverage",
     "prepare": "npm run build",
-    "preversion": "gulp version:update"
+    "version": "gulp version:update"
   },
   "bundlesize": [
     {