Default models support for Spring's Autowired

[lazaroclapp]

This adds support for spring's @Autowired annotation as both a way to exclude fields from initialization checking (since Spring will inject them before any methods are called), and to mark methods as initializers. See Spring's documentation and the discussion in #396

This is based on the original PR #475 contributed by @chat-eau-lumi (note CLA signature in that PR). It adds fixes to test cases, particularly around importing Spring classes and the constructor usage of @Autowired, contributed by @lazaroclapp.

[lazaroclapp]

@chat-eau-lumi Can you take a look and make sure the Spring code for the tests is what you had in mind? It doesn't exactly need to run (since it's not being processed by the Spring annotation processor), but it should look as close to real Spring code demonstrating both @Autowired uses as possible.

[coveralls]

Pull Request Test Coverage Report for Build #533

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 89.162%

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Files with Coverage Reduction	New Missed Lines	%
src/main/java/com/uber/nullaway/ErrorProneCLIFlagsConfig.java	3	95.45%

Totals
Change from base Build #532:	0.0%
Covered Lines:	3480
Relevant Lines:	3903

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💛 - Coveralls

[chat-eau-lumi]

Yes, it looks good! I'm used to writing public Test() instead of public init(), but it looks like init() covers the constructor case just fine.

[msridhar]

LGTM

[lazaroclapp]

Yes, it looks good! I'm used to writing public Test() instead of public init(), but it looks like init() covers the constructor case just fine.

Wait a moment. Clarification: the point of making @Autowired methods initializers is to have methods which are not constructors but are annotated as @Autowired be considered initializers from the point of view of NullAway. The class constructor (Test()) is always an initializer and always checked for which fields it does or doesn't initialize.

Am I misunderstanding what @Autowired on a method means here? When would you normally use that annotation in a method (as opposed to a field)?

[chat-eau-lumi]

Sorry, I mistook the Autowired initializers case for the Autowired contructors case for some reason! I usually see Autowired setter methods, but you're right- in general it's used for initializer methods.

[lazaroclapp]

Checking the docs, it seems that what this PR does makes sense, even if it doesn't cover all the semantics of Spring's @Autowired. Will re-run CI after rebasing and land this once all checks pass :)