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POWhy does bnd add a uses directive for a package used only within a method body?
 

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  1. POWhy does bnd add a uses directive for a package used only within a method body?
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    <p>I have a project with a single source file, listed here in its entirety:</p> <pre><code>package com.acme.el; public class ExpressionUtils { public static Object evaluate() { new org.apache.commons.el.ExpressionEvaluatorImpl(); return null; } } </code></pre> <p>The functionality is irrelevant to the question. When I build the project as an OSGi bundle using Gradle, the manifest contains the following instruction:</p> <pre><code>Export-Package: com.acme.el;uses:="org.apache.commons.el";version="1.0" </code></pre> <p>What baffles me is that <code>uses</code> directive. As I've understood the directive, it is meant to define dependencies on other packages that need to be propagated to other bundles importing this exported package - if my class definitions or method signatures refer to classes in the <code>org.apache.commons.el</code> package, for instance. But in this class, the dependency on <code>org.apache.commons.el</code> is completely contained <em>within the body</em> of a method. It is not exposed in the API, and no other bundle importing <code>com.acme.el</code> could ever get a hold of the <code>ExpressionEvaluatorImpl</code> instance created in the method. So the dependency shouldn't need to be propagated, right? </p> <p>Did I misunderstand the meaning of the <code>uses</code> directive, or is its use here unnecessary?</p> <p>I made <a href="https://github.com/emlun/bnd-uses-strange">a minimal example GitHub repo for reproduction</a> which you can clone and import as a Gradle project in Eclipse.</p>
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    1. USEmil Lundberg
    1. USEmil Lundberg
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    1. COI've read section 3.7.5 Package Constraints of the OSGi spec v4.3.0, but it didn't make me much wiser on this. This is all that is said about when to use the `uses` directive, the rest discusses how the framework should handle these directives: _[...] For example, when they extend classes from another package, or these other classes appear in method signatures. It can therefore be said that a package **uses** other packages. These inter-package dependencies are modeled with the uses directive on the Export-Package header._
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      1. USEmil Lundberg
    2. COYour understanding of the "uses" constraint is correct, so it's not clear to me why the constraint is being generated by bnd in this case. If you're absolutely sure there are no other references to the package elsewhere, then you may have found a bug; please report it at https://github.com/bndtools/bnd/issues
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      1. USNeil Bartlett
    3. COYes, I'm absolutely sure - I created a minimal example containing only that one class listed in the question, which you can see for yourself at the linked GitHub repo. :)
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