Add support for the 'externally_connectable' property for Chrome builds

[BrentM]

Background

In an upcoming release, AdBlock on Chrome will start using the Chrome message passing API - chrome.runtime.onMessageExternal. In order to do so, the buildtools need to support rendering appropriate values for
​externally_connectable into the generated manifest.json

Since this isnt' the first time (and probably won't be the last time) that some arbitrary values need to be added to the manifest.json, we want to support some generic rendering from a metadata.* to a manifest.json

What to change

Implement a machinery which takes arbitrary key/value pairs from a manifest-section of a metadata.*-file and implicitly renders them into the generated manifest.json.

Let the parsing follow these rules:

• An option's key may be declared as a series of nested dictionary keys, seperated by '.'.
• Declaring an option's value in a new line (even if only one is given) will define the option's value as a list.
• When an option's value is defined as a list, no other nested objects may follow.
• A list is expandable by the ConfigParser's '+=' token (Note: A previously declared string will be converted into a list).
• Values may be marked as number or bool by prefixing them accordingly (this also applies to values in a list):
  • bool:<value>
  • number:<value>

Integration Notes

Values in metadata.* that are supposed to be lists must now separated by newlines, instead of spaces (with the first items starting in a newline after the option itself).

[BrentM]

I've attached files that have been updated with what I believe are the required changes.

[tlucas]

Hey Brent, thanks for providing the changes!

I wonder if you intentionally only added the matches-key?
FWIW i'll add ids and accepts_tls_channel_id too, to fully support externally_connectable-

[BrentM]

I only did the minimum amount that we needed :) Thanks for adding the other options.

[tlucas]

Replying to BrentM:

I only did the minimum amount that we needed :) Thanks for adding the other options.

Alright - i adjusted the description accordingly.

[abpbot]

A commit referencing this issue has landed:
​Issue 6552 - Support arbitrary manifest values

[tlucas]

@Brent, the patch is now in master.
Please have a look at the example metadata in tests, it should be exactly what you need:

​https://hg.adblockplus.org/buildtools/diff/8055aac42982/tests/metadata.chrome#l1.26

Best, Tristan

[abpbot]

A commit referencing this issue has landed:
​Issue 6552 - call setdefault() on correct dictionary

[BrentM]

Thanks I'll take a look.