Add default version of export to selfimports

[chrisrueger]

This is an thought-experiment / prove of concept / based on discussion for #6220.
Relates to #6220 (comment)

In this PR

• after exports and imports have been processed in Builder.analyze()
• we calculate self-imports
• and then call augmentImports(selfImports, exports) to applyVersionPolicy() to any of those self-imports which
  a) do not yet have a version or
  b) specify a range-mask with the rang macro (e.g. Import-Package: example.c;version="${range;[==,=+)}")
• -nodefaultversion true still works and could disable the behavior

Based on the observation in #6220 (comment) the following will happen for this bnd:

.bnd:

Bundle-Version: 1.0.1
-exportcontents: example.a, example.b, example.c
Import-Package: example.c;version="${range;[==,=+)}", *

MANIFEST.MF:

Bundle-Version: 1.0.1
Export-Package: example.a;uses:="example.b";version="1.0.1",example.b;version="1.0.1",example.c;version="1.0.1"
Import-Package: example.b;version="[1.0,2)",java.lang,example.c;version="[1.0,1.1)"

instead of as it was before:

Export-Package: example.a;uses:="example.b";version="1.0.1",example.b;version="1.0.1",example.c;version="1.0.1"
Import-Package: example.b,java.lang,example.c;version="${range;[==,=+)}"

Why or When would that be useful?

As outlined in #6220 3rd-party depdencies like Gson etc. use bnd to create OSGi bundles via the maven or gradle plugins.
But often there is no OSGi-knowledge present hence there are often no version information at the package-level like:

• packageinfo file in the package directory (recommended)
• package-info.java, bnd’s Version annotation
• Manifest of the exporting JAR

Only a Bundle-Version is usually mainted.

For all those dependencies out there the previous behavior already added the Bundle-Version as the last resort to Exports, while self-imports would not get any version information.

But now the self-imports would get the version information from the export even it is the "last resort" Bundle-Version

Open Questions

• what about if this be the (new) default behavior?
• does it even make sense?
• what could go wrong if this would be the new default? What could it break?
• or should there be a new option / instruction to enable this behavior?

Feedback appreciated @pkriens @bjhargrave

[bjhargrave]

This is a bad idea. Because export defaults to using Bundle-Version does not mean it is a valid choice on the import side. There is probably no other bundle which exports the package at the Bundle-Version of the importer. So matching the import at the Bundle-Version will be pointless. Bundle-Version is not semantic and thus not suitable for use on imports.

Exporters need to use proper versions. Importing at the Bundle-Version is a bad idea. So I would reject this proposed change.

[chrisrueger]

Thanks @bjhargrave for the feedback.

I am just wondering if there is any other way out of the situation described in eclipse-jdtls/eclipse.jdt.ls#3236 (comment) other than manually fixing in upstream (gson).

The problem, as you've noted, is that both gson bundles import just "com.google.gson.annotations" (implied >= 0.0.0) leaving the door open for resolution between different versions of the same library 😐 gson 2.10.1 should import with a range of [2.10.1,2.11.0) and gson 2.11.0 should import with a range of [2.11.0,2.12.0) to be safe.

com.google.gson_2.10.1.jar
Import-Package = sun.misc;resolution:=optional,com.google.gson.annotations;version="[2.10.1,2.11.0)"

com.google.gson_2.11.0.jar
Import-Package = sun.misc;resolution:=optional,com.google.gson.annotations;version="[2.11.0,2.12.0)"

My interpretation is that gson "expects" that its own com.google.gson.annotations is imported, but apparently another bundle of the same library got wired.

[bjhargrave]

The solution is always to fix the upstream :-)

In the alternate, if the bundle must not import the package from another bundle, then its bnd instructions should decorate the export with -noimport:=true. Then it won't self-import and will just export. When the bundle goes to access the package, it will always use its own copy since it can never import the package.

[chrisrueger]

Closing. Continue at comment #6220 (comment)