[plugin-helpers] npm -> yarn (#16632)

* [plugin-helpers] npm -> yarn

* Allow globs to not match when singular, e.g. for 'yarn.lock'

* --frozen-lockfile

1 files changed, 2 insertions, 10 deletions

diff --git a/packages/kbn-plugin-helpers/tasks/build/create_build.js b/packages/kbn-plugin-helpers/tasks/build/create_build.js
index aad1ec9e2..3ba73cee5 100644
--- a/packages/kbn-plugin-helpers/tasks/build/create_build.js
+++ b/packages/kbn-plugin-helpers/tasks/build/create_build.js
@@ -1,6 +1,5 @@
 const join = require('path').join;
 const relative = require('path').relative;
-const statSync = require('fs').statSync;
 const execFileSync = require('child_process').execFileSync;
 const del = require('del');
 const vfs = require('vinyl-fs');
@@ -17,7 +16,7 @@ module.exports = function createBuild(plugin, buildTarget, buildVersion, kibanaV
     .then(function () {
       return new Promise(function (resolve, reject) {
         vfs
-          .src(files, { cwd: buildSource, base: buildSource })
+          .src(files, { cwd: buildSource, base: buildSource, allowEmpty: true })
           // modify the package.json file
           .pipe(rewritePackageJson(buildSource, buildVersion, kibanaVersion))
 
@@ -39,13 +38,6 @@ module.exports = function createBuild(plugin, buildTarget, buildVersion, kibanaV
         stdio: ['ignore', 'ignore', 'pipe'],
       };
 
-      try {
-        // use yarn if yarn lockfile is found in the build
-        statSync(join(buildRoot, 'yarn.lock'));
-        execFileSync(winCmd('yarn'), ['install', '--production'], options);
-      } catch (e) {
-        // use npm if there is no yarn lockfile in the build
-        execFileSync(winCmd('npm'), ['install', '--production', '--no-bin-links'], options);
-      }
+      execFileSync(winCmd('yarn'), ['install', '--production', '--frozen-lockfile'], options);
     });
 };