Description Stephan Herrmann 2019-05-25 15:13:09 EDT

I observed a combination of settings and source file that can confuse the analysis of @SuppressWarnings:


- configure the following options:

org.eclipse.jdt.core.compiler.problem.undocumentedEmptyBlock=error
org.eclipse.jdt.core.compiler.problem.fatalOptionalError=enabled

compile the following source:
//---
package p;

import java.util.List;

public class C {
	@SuppressWarnings("unused") private int i00, i01, i02, i03, i04, i05, i06, i07, i08, i09;
	@SuppressWarnings("unused") private int i10, i11, i12, i13, i14, i15, i16, i17, i18, i19;
	@SuppressWarnings("unused") private int i20, i21, i22, i23, i24, i25, i26, i27, i28, i29;
	@SuppressWarnings("unused") private int i30, i31, i32, i33, i34, i35, i36, i37, i38, i39;
	@SuppressWarnings("unused") private int i40, i41, i42, i43, i44, i45, i46, i47, i48, i49;
	@SuppressWarnings("unused") private int i50, i51, i52, i53, i54, i55, i56, i57, i58, i59;
	@SuppressWarnings("unused") private int i60, i61, i62, i63, i64, i65, i66, i67, i68, i69;
	@SuppressWarnings("unused") private int i70, i71, i72, i73, i74, i75, i76, i77, i78, i79;
	@SuppressWarnings("unused") private int i80, i81, i82, i83, i84, i85, i86, i87, i88, i89;
	@SuppressWarnings("unused") private int i90, i91, i92, i93, i94, i95, i96, i97, i98, i99;
	@SuppressWarnings("unused") private int j00, j01, j02, j03, j04, j05, j06, j07, j08, j09;
	
	@SuppressWarnings("rawtypes") List l;
	
	void empty() {
	}
}
//---


Observations:

We accumulate > 100 problems (110 of which are "unused private field").

We detect undocumented empty block, which is configured as error.

Due to fatalOptionalError we tag the MethodDeclaration with ignoreFurtherInvestigation.

During generateCode() for this method we invoke compilationResult.getProblems().

Since problemCount > maxProblemPerUnit we reduce the problems to 100.

After this, CompilationUnitDeclaration.finalizeProblems()
 - does not see hasMandatoryErrors so we proceed to analysie @SW
 - we find two @SW declarations for which the suppressed problem got deleted

In particular @SuppressWarnings("unused") gets the infamous
   "At least one of the problems in category 'unused' is not analysed due to a compiler option being ignored"

At @SuppressWarnings("rawtypes") we incorrectly get
   "Unnecessary @SuppressWarnings("rawtypes")"


I chose undocumentedEmptyBlock arbitrarily. Any optional problem configured to error will do.