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JEP 211: Elide Deprecation Warnings on Import Statements

Summary​

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.

Goals​

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.

Non-Goals​

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.

Description​

From a specification perspective, the needed change is small. In JLS 8 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 @Deprecated is used (overridden, invoked, or referenced by name) in a construct which is explicitly or implicitly declared, 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.

Testing​

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