polymer-build | Moved to Polymer/tools monorepo | Web Framework library

This error means that you load the same dependency from two different urls. For instance

After much deliberation I found a solution and thought I would document it here in case anybody ever runs into the same issue.

I have a parent polymer element called baseline-policies-tab.html within which baseline-policy-edit.html is a child element. To resolve the issue, I had to add an import statement for baseline-policy-basic-info.html to baseline-policies-tab.html.

Also, I changed the import statement in baseline-policy-edit.html from

So, it looks like catch is a reserved word in IE 9+. I found this nugget of information at https://github.com/lahmatiy/es6-promise-polyfill:

catch is a reserved word in IE<9, meaning promise.catch(func) throws a syntax error. To work around this, use a string to access the property:

promise['catch'](function(err) { // ... });

Or use .then instead:

promise.then(undefined, function(err) { // ... });

My code works in IE11 if I modify it to avoid catch, like so:

The reason for this was that in the polymer project were still some errors left. After the errors were solved, the task ended.

The original error is unrelated to the "alternate error".

While the build task runs gulp, npm run prioritizes the locally-installed gulp (at node_modules/.bin/gulp) before the system-installed gulp. Running gulp yourself (without npm run) would invoke the globally-installed gulp, which may result in an error if it's incompatible with your project (e.g., Gulp 3 binary with Gulp 4 API in your scripts, which appears to be the case). You could either install Gulp 4 so that you can run gulp yourself, or continue using npm run build.

To troubleshoot the original error, I recommend starting from the Polycast's original source (if you haven't already) to determine what the difference could be.

If you prefer to stick with your current track, I suggest a few things:

• Verify the paths in your HTML imports, as a path to a non-existent file would cause a silent error (polymer-build issue 88). It might be helpful to run polymer build -v (verbose build).
• Add buildStream.on('error', (err) => console.log(err)) after let buildStream = ... in case any unsuppressed error events crop up in that stream.

I noticed a bug in the generator in that the starter-kit subgenerator was missing a dependency on webcomponentsjs, which would cause an error with polymer-build. And as you discovered, polymer.json was also missing dependencies for the polyfill support of webcomponentsjs, which caused 404s on polyfilled browsers (such as Linux Chrome). That's all fixed now in v0.0.6.

You'll also need a version of polymer-build that does not try to uglify the JavaScript, which would fail due to its inability to recognize ES6. The new-build-flags branch of the polymer-cli repo replaces uglify with babili for ES6 minification (added in PR#525). You could check out that branch and build it yourself, or you could install it from here:

merge-stream is already declared as a devDependency in package.json, so the error indicates either you haven't installed the dependencies, or that package is somehow deleted from your dependency store (i.e., node_modules/).

To install only merge-stream, you'd run this from the project's root directory:

The Polymer Analyzer supports standard JavaScript. If you're writing in some alternate syntax, you need to transform that syntax out before it hits the Analyzer. The polymer-build library is made for this use case. You can build a Gulp pipeline and before files reach the Analyzer, perform your custom transforms.

See the polymer-build library here: https://github.com/Polymer/polymer-build

Hope that helps!