Make tfjs-layers compatible with the closure compiler

[dsmilkov]

• Add /** @nocollapse */ on static properties to tell closure not to remove them.
• Prepend declare in front of interfaces and types that are external (used in json deserialization/serialization) so closure doesn't rename their properties.
• Instead of object literals, explicitly assign each field separately to a config object and mark it as serialization.ConfigDict so closure doesn't rename its properties.

Similar changes in tfjs-core: tensorflow/tfjs-core#1521

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This change is 

[caisq]

cc @ericdnielsen , @bileschi , @davidsoergel as an FYI.

[dsmilkov]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @caisq, @davidsoergel, and @nsthorat)

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src/engine/container.ts, line 775 at r1 (raw file):

    const theConfig = this.getConfig();
    const modelConfig: serialization.ConfigDict = {};
    modelConfig.className = this.getClassName();

FYI, this is a known issue with Closure. You can't do object literals even if you immediately assign them to a variable that is marked as being an external interface, such as ConfigDict. You have to assign each field individually.

[caisq]

@dsmilkov Thank you for spending the time and effort in making the code compile with closure.

Is there a way to ensure that going forward, people making changes in tfjs-layers will not break the closure compiler?

[davidsoergel]

Reviewed 24 of 24 files at r1.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @caisq, @davidsoergel, and @nsthorat)

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src/engine/container.ts, line 775 at r1 (raw file):

Previously, dsmilkov (Daniel Smilkov) wrote…

FYI, this is a known issue with Closure. You can't do object literals even if you immediately assign them to a variable that is marked as being an external interface, such as ConfigDict. You have to assign each field individually.

There are tons of object literals in our tests. I guess it's OK there?

[dsmilkov]

So an idea is to setup a weekly cron job to sync layers and test compilation with closure by executing a few pre-trained models (most of these problems only show up on run-time when code is compiled with aggressive closure rewriting rules).

We don't sync existing tests at all.