anomaly with apidiff output

[Stuart Marks]

Hi Apidiff Devs,

I'd like to report an anomaly with apidiff. I made a recent change to the JDK 
specification, which can be seen here:

  
https://github.com/openjdk/jdk/compare/master...stuart-marks:jdk:JDK-8138614-relax-new-string-requirement

This is a change to the doc comments of four AbstractStringBuilder methods: 
subSequence, substring(i), substring(i, i), and toString(). Note that ASB is a 
non-public class which has two public subclasses, StringBuffer and StringBuilder. 
Thus there should be a total of eight changes: four methods in each of the two 
public classes.

I did two javadoc runs: one on the tip of this branch ("new") and one for its right 
parent which is the commit from master that was merged into it ("old"). The diffs 
are minimal. The javadoc output is as expected: I can see changes in the specs of 
four methods in each of the StringBuilder and StringBuffer classes.

I build apidiff from source a couple weeks ago. The command line I ran was something 
like:

     apidiff --api old --api-directory javadoc-old \
         --api new --api-directory javadoc-new \
         --include 'java.base/java.lang.*' --output-directory sb.apidiff

(Where javadoc-old and javadoc-new are the respective javadoc output directories.) 
It seemed mostly successful in that it inspected all the java.lang classes, and it 
found differences in the right files.

The output is visible here:

     https://cr.openjdk.org/~smarks/misc/sb.apidiff/

However, the actual differences it found were incorrect. The diffs for StringBuffer 
seem correct. However, for StringBuilder, only one difference is shown, for the 
toString() method. The diffs for the other methods are missing. Also, perhaps 
significant, is that a couple other methods are missing from StringBuilder, 
setCharAt() and setLength(), though there aren't any differences in the specs of 
these methods.

Daniel Fuchs suggested that https://bugs.openjdk.org/browse/CODETOOLS-7903843 might 
be related. Indeed it might be, but I can't tell.

Anyone have any ideas? I can file a bug with this info if it's helpful.

s'marks