polymer: dart2js transformers should not run in "pub serve" with Dartium

[DartBot]

<img src="https://avatars.githubusercontent.com/u/1081711?v=3" align="left" width="96" height="96"hspace="10"> Issue by jmesserly
Originally opened as dart-lang/sdk#19168

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I think this is the issue Alan was seeing...

Polymer is supposed to work out-of-the-box in Dartium w/o transforms. All of our transforms are deploy time optimizations or just part of making HTML+dart2js work:

• inline HTML imports
• smoke -- polyfill reflection on dart2js
• optimized @­observable objects
• extract inline <script> into dart files
• collect all <script>s for dart2js
• ... possibly a few other things I'm forgetting ...

[DartBot]

<img src="https://avatars.githubusercontent.com/u/1081711?v=3" align="left" width="48" height="48"hspace="10"> Comment by jmesserly

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Added Pkg-PolymerBuild label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/1081711?v=3" align="left" width="48" height="48"hspace="10"> Comment by jmesserly

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Added Area-Pkg label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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This is exactly what Bob and I were discussing this morning.

It's tricky because pub-serve is used both for serving for dartium and for serving for Chrome/FF so people can also iterate there. For the former we want no transformations to be run, for the latter we want all transformations to run. We also want that the entrypoint file that the user loads (index.html) to be the same in both cases.

We can work on making our transformers lazy, but we need from pub a mechanism so we can choose not to run transformers given a particular user agent.

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cc @nex3.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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Marked this as being blocked by dart-archive/barback#50.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/1081711?v=3" align="left" width="48" height="48"hspace="10"> Comment by jmesserly

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ah right. seems Dartium vs non-Dartium is the crucial distinction.

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Changed the title to: "polymer: dart2js transformers should not run in "pub serve" with Dartium".

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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After discussing this more throughout the day. Seems that the best solution we have so far is to have 2 entrypoints for polymer apps when running in pub-serve. Say you have an app with 'web/index.html' as the entrypoint.

What we'll do is the following:

• web/index.html has a small transformer that injects a small .js script tag upfront
• if the script detects that Dart is available, there is nothing else to do, we let the rest of the page load as usual
• otherwise, we use a redirect to change the browser to point at web/index-js.html
• index-js.html is the result of a lazy transformer that does everything we need.

I'm marking now this blocked on issue dart-archive/code_transformers#17, since that's how we will be able to implement the lazy transformer. In particular, we need to be able to rewrite smoke's mirror import lazily, and since that modifies code in another package, it would need to be handled as a global transformation. We can possibly also run the observe transformers lazily, so we could avoid all work in Dartium.

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Marked this as being blocked by dart-archive/code_transformers#17.
Unmarked this as being blocked by dart-archive/barback#50.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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Marked this as blocking #401.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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Added this to the 1.6 milestone.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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Added Priotiy-Medium label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2049220?v=3" align="left" width="48" height="48"hspace="10"> Comment by sigmundch

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Removed Priority-Unassigned, Priotiy-Medium labels.
Added Priority-Medium label.