pub build packages directory for a Polymer app is too big

[DartBot]

<img src="https://avatars.githubusercontent.com/u/224266?v=3" align="left" width="96" height="96"hspace="10"> Issue by johnmccutchan
Originally opened as dart-lang/sdk#19521

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Reproduction steps:

$ cd runtime/bin/vmservice/client
$ pub build --mode=release

Look in build/web/packages

Specifically,

824K ./packages/polymer/src/js/polymer

That directory has two copies of polymer.js (polymer.js and polymer.concat.js). It also has two map files.

1.6M ./packages/web_components

Same problem here, directory has two copies of platform.js (platform.js and platform.concat.js). It also has two map files (each are half a meg in size!).

I'm not sure why .map files are being included in release mode build output.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2156198?v=3" align="left" width="48" height="48"hspace="10"> Comment by kasperl

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Added Triaged label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/224266?v=3" align="left" width="48" height="48"hspace="10"> Comment by johnmccutchan

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Short term question: Can I safely delete one of the copies of each?

[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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That's a good point. We could remove the *.concat.js versions in release mode.

The main challenge is how. I can imagine 2 options:
  - self-transformers: we could add a transformer to web_components and polymer to respectively remove part of their own code. This might slow down the build of polymer apps enough that we might want to do this differently. In particular, until pub-serve can use some sort of import-hooks, it does a lot of work just to load an extra transfomer.
  - global transformers: we are already planning to move polymer, smoke, and maybe observe to become part of a global-polymer transformer (see issue dart-lang/sdk#9), so it might make sense to put this there too.

As for your question in #­2, yes. You can safely delete the *.concat.js files and the .map files after you build in release mode.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/224266?v=3" align="left" width="48" height="48"hspace="10"> Comment by johnmccutchan

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Thanks Siggi!

Removing the *.concat.js files reduced the compiled Observatory size by 0.5MB (or 25%). We were already removing the *.map files.

[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.
Removed Pkg-Polymer label.
Added Pkg-PolymerBuild, Area-Pkg labels.

[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 this from the 1.6 milestone.
Added Polymer-P-1 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 Polymer-P-1 label.
Added Polymer-Milestone-Next 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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Added PolymerMilestone-Next 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 Polymer-Milestone-Next label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2156198?v=3" align="left" width="48" height="48"hspace="10"> Comment by kasperl

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Added this to the 1.6 milestone.