Lint stuck after upgrading gradle plugin to 2.3.0

app:lint hangs after I upgraded the gradle plugin to 2.3.0.

Unexpected failure during lint analysis (this is a bug in lint or one of the libraries it depends on)

It complains about ProblemReporter.isClassPathCorrect(ProblemReporter.java:4761) and other places in ProblemReporter, but I was not able to pinpoint the problem.

Turns out this is caused by libraries that uses old lint APIs, in my case Timber and Butterknife. Once I updated those dependencies, lint finishes.

Thanks Josh Burton for sharing his solution with me!

Constraint Layout beta5 lint error

Constraint Layout beta 5 is the release candidate, and added a lint to deprecate older versions.

The easiest way to get rid of the lint error is to press Alt-Enter and choose the first option to upgrade.

However, I encountered a bug, which forces me to stay with beta4 until the next version comes out with the fix. I still want to get rid of the lint error so my continuous build does not fail. I didn't want to change lintOptions abortOnError to false in build.gradle because I still want my build to catch other fatal lint errors.

I tried to get Android Studio to fix this lint error for me by choosing Disable inspection from Alt-Enter. Alas, that only changed the local settings. Turns out that I need to go to Settings → Editor → Inspections to undo that.

The option I wanted is Suppress: Add tools:ignore="MissingConstraints" attribute, which modifies the xml for me to add the appropriate lint suppression.

<android.support.constraint.ConstraintLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:ignore="MissingConstraints">
<!-- Cannot upgrade to beta5 due to http://b.android.com/233863 -->

Finally, I added a comment to remind me why I suppress the lint error.

More info: Suppress Lint Warnings.