Dependency conflicts are extremely opaque
-----------------------------------------
Key: MNG-5138
URL: https://jira.codehaus.org/browse/MNG-5138
Project: Maven 2 & 3
Issue Type: Bug
Components: Dependencies
Affects Versions: 3.0.3
Reporter: Robert Watkins
Attachments: maven_dep_conflict.tgz
When you get conflicts between versions of dependencies - mostly transitive,
and mostly when using ranges - it is extremely hard to see where the conflicts
are coming from.
With Maven 2.2, you could use the -X argument to get extra information, and it
was possible to see where versions were detected and where conflicts were
coming from. This is no longer the case with Maven 3, probably due to the use
of Aether.
In the attached tar ball, there are three projects ('first', 'second' and
'third'), each generated using the maven:archetype plugin.
'first' depends on commons-lang:commons-lang:[2.5]
'second' depends on commons-lang:commons-lang:[2.6]
'third' depends on both 'first' and 'second'.
When you do 'mvn clean install' on 'third', you get the following output:
$ mvn clean install
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building third 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.825s
[INFO] Finished at: Tue Jul 26 21:59:46 EST 2011
[INFO] Final Memory: 3M/81M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project third: Could not resolve dependencies
for project net.twasink:third:jar:1.0-SNAPSHOT: Failed to collect dependencies
for [net.twasink:first:jar:1.0-SNAPSHOT (compile),
net.twasink:second:jar:1.0-SNAPSHOT (compile), junit:junit:jar:3.8.1 (test)]:
Could not resolve version conflict for [commons-lang:commons-lang::jar] with
requested versions [2.6,2.6], [2.5,2.5] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e
switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please
read the following articles:
[ERROR] [Help 1]
http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException
Using -X and -e gives you stack traces but no more meaningful information.
Ideally, the normal output should indicate the transitive paths - e.g. that
commons-lang:2.5 is being brought in by 'first' and 2.6 by 'second'. Failing
that, the debug output could log the transitive paths, as Maven 2.2 did. While
this is an obviously simple and contrived example, real-world projects using
ranges can get a lot more complex.
Alternatively, if there is a way from the Maven CLI to switch on logging for
Aether, that might help as well.
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