Draft JEP: Elide deprecation warnings on import statements

Joe Darcy joe.darcy at oracle.com
Wed Feb 5 12:20:01 PST 2014


Below is the text of a draft JEP we are considering submitting for JDK 9.




As of Java SE 8, java compilers are required by reasonable
interpretations of the Java Language Specification to issue
deprecation warnings when a deprecated type is imported by name or
when a deprecated member (method, field, nested type) is imported
statically. These warnings are uninformative and should not be
required. Deprecation warnings at actual uses of deprecated members
should remain.


The goal of this JEP is to facilitate making large code bases clean of
lint warnings. The deprecation warnings on imports cannot be
suppressed using the @SuppressWarnings annotation, unlike uses of
deprecated members in code. In large code bases like that of the JDK,
deprecated functionality must often be supported for some time and
merely importing a deprecated construct does not justify a warning
message if all the uses of the deprecated construct are intentional
and suppressed.


It is not a goal of this JEP to actually resolve all the deprecation
warnings in the JDK code case. However, that might occur as part of a
separate maintenance effort in JDK 9.


 From a specification perspective, the needed change is small. In JLS 7
(text in JLS 8 will be similar), the section on @Deprecated states:

"A Java compiler must produce a deprecation warning when a type,
method, field, or constructor whose declaration is annotated with the
annotation @Deprecated is used (i.e. overridden, invoked, or
referenced by name), unless:

     * The use is within an entity that is itself annotated with the
       annotation @Deprecated; or

     * The use is within an entity that is annotated to suppress the
       warning with the annotation @SuppressWarnings("deprecation"); or

     * The use and declaration are both within the same outermost class."

The specification change would be something like adding another bullet
stating the additional exclusion:

     * The use is within an import statement.

In the javac reference implementation, there would be a simple check
to skip over import statements when looking for deprecation warnings.


Normal unit tests should suffice to test this feature. A handful of
JCK tests may need to be updated for the changed specification.


   - Other JDK components: The change would ease getting and keeping
      the JDK code base free of deprecations warnings.
   - Compatibility: Since warning will be issued in fewer cases, there 
is negligible compatibility impact.
   - User experience: Fewer uninformative warnings will be issued by the 
   - TCK: As noted earlier, a handful of JCK test may need updating.

More information about the compiler-dev mailing list