Github user revans2 commented on a diff in the pull request:
https://github.com/apache/storm/pull/736#discussion_r40823287
--- Diff: DEVELOPER.md ---
@@ -222,6 +222,11 @@ To pull in a merge request you should generally follow
the command line instruct
# Build the code and run the tests
+Storm has some oddities with packaging and plugin dependencies. We build
our own plugins and shade storm-core,
+but have sub-modules that depend on storm-core. Because of this the build
needs to be split into two parts.
--- End diff --
Essentially what happens is that if you build a multi-module project where
one module depends on another module that is a part of the same build, maven
tries to be smart and will use the pom.xml and .jar or .class directory from
the module that is a dependency.
So if we have a project set up like the following where we have b depends
on a, and a is shaded. b will see different versions of the code and pom.xml
from a depending on what maven command is run.
- base/
- pom.xml
- a/
- pom.xml
- dependency-reduce-pom.xml
- target/
- classes/
- a.jar (shaded)
- a.orig.jar (no-shaded)
- b/
- pom.xml (depends on a)
If I run `mvn clean compile` the classpath for compiling b will include
`base/a/target/classes` which is not shaded, and if b is written to use a
shaded class it will fail to compile. b will also see the full set of
non-shaded dependencies from a, so if b is creating an uber jar, it will assume
that all of those dependencies will be provided by a, when in reality they will
not be.
If I run `mvn clean package` or `mvn clean install` b will see the shaded
a.jar on its classpath, but it will still see the full non-shaded set of a's
dependencies.
The only way I found to make b use the dependency-reduced-pom.xml from a,
is to first build/install a without b, and then build/install b without a.
That way a will install the shaded jar and dependency-reduced-pom.xml into the
local repository. Then b will get its dependencies from the local repo instead
of trying to rebuild a.
I'll try to add this to the documentation.
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