[xdl] Do not override google-services.json contents since SDK37

[sjchmiela]

Why

Following Using FCM doc or GoogleSignIn - Usage with Firebase part would not render the expected results — googleSignIn configuration was always being applied onto google-services.json, even if a custom one has been provided by the user. Most probably this is not how this should work or what the user expect.

When pushed to Turtle builders, should fix expo/expo#7727.

How

Depending on the SDK version of the built project:

• if the SDK is >= 37:
  • only change google-services.json if none was provided (so we're operating on a placeholder one)
  • if both configuration settings are provided print a warning and not modify the custom google-services.json
• if the SDK is < 37:
  • if the user provides a custom googleServicesFile, print a warning that its contents are about to be modified,
  • always modify google-services.json, as it has been working before.

I have also moved the replace "host.exp.exponent" with ${javaPackage} to where the logic above is mentioned so that all google-services.json modifications are in one place.

Test plan

• SDK37, only googleServicesFile — job, no warning, used google-services.json
• SDK37, only googleSignIn — job, no warning, uses placeholder project ID and googleSignIn key
• SDK37, both provided — job, warning present (google-services.json overrides others), used google-services.json
• SDK36, only googleServicesFile — job, no warning, removed key from google-services.json force-pushed version where the warning should be printed and the key still removed
• SDK36, only googleSignIn — job, no warning, used googleSignIn and leaking project ID
• SDK36, both provided — job, warning present (google-services.json overridden), google-services.json overridden

[codecov-io]

Codecov Report

Merging #1897 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1897   +/-   ##
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  Coverage   60.77%   60.77%           
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  Files          84       84           
  Lines        2598     2598           
  Branches      719      719           
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  Hits         1579     1579           
  Misses        996      996           
  Partials       23       23           

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[MarzV]

@sjchmiela, First of all, thnkz for addressing this issue, lot of people depend on this feature. But can can you please eleborate on this a bit more in detail in the scenario that a build is made with SDK 36

Before this issues was raised, I did not have the extra code in my app.json for the google.service.json. I mean this snippet of code:

"android": {
"package": "secret",
"googleServicesFile": "./google-services.json",
"config": {
"googleSignIn": {
"apiKey": "xxxxxxxxxxxxxxxx"
}
},
"versionCode": 1
},
}

But after the moment issues where raised that pushtoken was no longer set for standalone apps. there was a suggestion that adding the above code would fix the problem, so I did.

Question: When building with SDK 36 do we still need to add the above extra snippet of code, even when before it was not there and everything worked just fine. Or do we now always need to add this extra code snippit to the app.json file.?

Your answer is much appreciated