Consider adopting NullAway into the build process

[trustin]

See: https://github.com/uber/NullAway

[anuraaga]

Ah yeah now I remember this issue. Seems NullAway is a faster but potentially less precise checker good enough for almost all cases. But can't find any good resource listing out what cases it misses vs checker framework. Do you have any idea?

[trustin]

No. 😄 I didn't take a close look at all. IIRC JetBrains had some contract annotations, too. Not sure which is the best 🤔

[ikhoon]

I tried to test and compare NullAway and the Checker Framework.

The Checker Framework - It does not support Java 13 yet.

> org.checkerframework.javacutil.UserError: 
The Checker Framework cannot be run with JDK 13+.  You are using version 13. Please use JDK 8 or JDK 11.

So I don't think we need to go any further now.

NullAway

It produces some useful error messages. But it could not cover all of our null checking code.
For example, it does not recognize null checking in checkArgument(). uber/NullAway#47

armeria/core/src/main/java/com/linecorp/armeria/common/SessionProtocol.java

Lines 87 to 88 in bd28eb2

	checkArgument(value != null, "unknown session protocol: ", uriText);
	return value;

SerializationFormat.java:131: error: [NullAway] returning @Nullable expression from method with @NonNull return type

I am not sure that we can put NullAway into the build process.
Anyway, I am going to make a PR to fix True Positive errors detected by NullAway. 😀

[anuraaga]

@ikhoon Since checker framework also can't be run together with error prone from what I understand, we'd have two builds anyways, and I guess with some configuration tweaks that could be set to Java 11. Probably not worth the trouble though, but I'm curious whether checker framework would catch checkArgument. Do you have a branch I can play with (or you can try playing with Java 11? :D)

[ikhoon]

Since checker framework also can't be run together with error prone from what I understand,

It looks resolved in Error Prone 2.4.0
https://github.com/kelloggm/checkerframework-gradle-plugin#incompatibility-with-error-prone

Do you have a branch I can play with (or you can try playing with Java 11? :D)

Yeah, let me push the branch tested locally.

[ikhoon]

@anuraaga This is https://github.com/ikhoon/armeria/tree/nullness 😀