This sounds like time being spent running the polymer transformers. Siggi, could they take 6-7s worth of time?

cc @sigmundch.

It could - when do you pub-build pub reports about 5-6 seconds running polymer on TodoMVC. Most of the time is running the resolver (which might be loading and analyzing the entire SDK).

I haven't tried, but we could provide a mock SDK to the analyzer that only contains what we need. But the analyzer might already have this planned.

A bit of barback instrumenting seems to confirm this: running ScriptCompactor on web/index.html takes about 5.6s on my machine. I'll bump this over to polymer.

cc @munificent.
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For now, I'm going to investigate making the build faster with a mock SDK for the analyzer as a temporary workaround, but long term, I believe we should invest in a solution that allow us to not run transformations when launching an app for development in Dartium.

Bob and I had a long brainstorming discussion this morning about what we could do to address this, but it requires non-trivial changes. For example, one attractive idea we had was to use the user-agent to decide how transformers are run, similar to namespaces ideas you had discussed in the past.

FYI - here is a change that let us mock out the SDK. It's an improvement, but it's not perfect:

https://codereview.chromium.org/315813003/

It takes TodoMVC from 4.8s in my machine, to 2.7s. The analyzer still resolves the entire application. I could make mocks for parts of the libraries that are known to us (like polymer), but I'm not sure about that. It already feels brittle with the current change.

The ultimate solution is to be lazy and not run any of the transformers in TodoMVC.

See: issue #19168

This is significantly improved by polymer 0.10.1 . There's still more to do, but we're in good shape for 1.5 .

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This issue has been moved to dart-archive/polymer-dart#201.