<p dir="auto">According the [development setup] (<a href="https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup">https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup</a>) I do the following:</p>
<ul dir="auto">
<li>clone vue repository</li>
<li><code class="notranslate">npm install</code></li>
<li><code class="notranslate">npm test</code></li>
</ul>
<p dir="auto">On <code class="notranslate">npm run build -- vue.min.js &amp;&amp; node test/e2e/runner.js "--env" "phantomjs"</code> step<br>
I get error:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="vue@2.1.5 test:e2e C:\vue_github
&gt; npm run build -- vue.min.js &amp;&amp; node test/e2e/runner.js &quot;--env&quot; &quot;phantomjs&quot;


&gt; vue@2.1.5 build C:\vue_github
&gt; node build/build.js &quot;vue.min.js&quot;

Error: Could not load C:\vue_github\src\core/index (imported by C:\vue_github\src\entries\web-runtime.js): ENOENT: no such file or directory, open 'C:\vue_github\src\core\index'
    at C:\vue_github\node_modules\rollup\dist\rollup.js:8833:10
    at process._tickCallback (internal/process/next_tick.js:103:7)
    at Module.runMain (module.js:606:11)
    at run (bootstrap_node.js:394:7)
    at startup (bootstrap_node.js:149:9)
    at bootstrap_node.js:509:3
Starting selenium server... started - PID:  10820

[Commits] Test Suite
========================

Running:  commits
"><pre class="notranslate"><code class="notranslate">vue@2.1.5 test:e2e C:\vue_github
&gt; npm run build -- vue.min.js &amp;&amp; node test/e2e/runner.js "--env" "phantomjs"


&gt; vue@2.1.5 build C:\vue_github
&gt; node build/build.js "vue.min.js"

Error: Could not load C:\vue_github\src\core/index (imported by C:\vue_github\src\entries\web-runtime.js): ENOENT: no such file or directory, open 'C:\vue_github\src\core\index'
    at C:\vue_github\node_modules\rollup\dist\rollup.js:8833:10
    at process._tickCallback (internal/process/next_tick.js:103:7)
    at Module.runMain (module.js:606:11)
    at run (bootstrap_node.js:394:7)
    at startup (bootstrap_node.js:149:9)
    at bootstrap_node.js:509:3
Starting selenium server... started - PID:  10820

[Commits] Test Suite
========================

Running:  commits

</code></pre></div>
<h3 dir="auto">Versions</h3>
<p dir="auto">Vue.js = 2.0.2<br>
Node.js = 6.9.1<br>
NPM = 4.0.2<br>
Windows 10</p>
<h3 dir="auto">Steps to reproduce</h3>
<ul dir="auto">
<li>Clone repo from GitHub</li>
<li>npm install</li>
<li>npm run build</li>
</ul>
<p dir="auto">or</p>
<ul dir="auto">
<li>Clone repo from GitHub</li>
<li>yarn install</li>
<li>yarn run build</li>
</ul>
<h3 dir="auto">What is Expected?</h3>
<p dir="auto">The expected behavior is that all versions of vue are build in the dist folder.</p>
<h3 dir="auto">What is actually happening?</h3>
<p dir="auto">Error: Could not load C:\Development\github\vue\src\core/index (imported by C:\Development\github\vue\src\entries\web-runtime.js): ENOENT: no such file or directory, open 'C:\Development\github\vue\src\core\index'<br>
at C:\Development\github\vue\node_modules\rollup\dist\rollup.js:8833:10<br>
at process._tickCallback (internal/process/next_tick.js:103:7)<br>
at Module.runMain (module.js:606:11)<br>
at run (bootstrap_node.js:394:7)<br>
at startup (bootstrap_node.js:149:9)<br>
at bootstrap_node.js:509:3</p>
<h3 dir="auto">Workaround</h3>
<p dir="auto">It appears that all imports that use the aliases defined in build/alias.js file do not work when the extension .js is not used. When .js is added to all imports, the build succeeds.</p>