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sbt-1.3.0-M2 breaks code that relies on URLClassLoader

See original GitHub issue

I’ve read the CONTRIBUTING guidelines

steps

Checkout airfame https://github.com/wvlet/airframe
Run sbt -Dsbt.version=1.3.0-M2 logJVM/testOnly *ResourceTest

problem

Some application needs to find files inside a jar file. To do so, we need to use the public method URLClassLoader.findResourceURLs(path) : Enumeration[URL]. ClassLoader has the same name method, but it’s defined as protected, so we cannot use the base ClassLoader.
Before sbt-1.3.0-M2, if we trace parent class loaders, we usually can find at least one URLClassLoader that can access resources inside jar files.
- Actually LayeredClassLoader, which is extending URLClassLoader, is found as a parent class loader, but it seems this class loader cannot find resources inside jar files.
Upgrading airframe to use sbt-1.3.0-M2 breaks the build https://github.com/wvlet/airframe/pull/457
- This is because no URLClassLoader that can find resources inside jar files can be found in this code: https://github.com/wvlet/airframe/blob/28a70c3fdc7a209eabf357548bdf7737c80e7b52/airframe-log/jvm/src/main/scala/wvlet/log/io/Resource.scala#L81-L90

expectation

sbt class loader should provide a URLClassLoader to get local resource URls.

notes

sbt version: 1.3.0-M2

Issue Analytics

State:
Created 4 years ago
Comments:17 (17 by maintainers)

Top GitHub Comments

1reaction

eatkinscommented, Apr 3, 2019

Should be fixed in #4601

ethanatkins@Ethans-MacBook-ProZ:~/work/oss/sbt/community/airframe$ sbt8 -Dsbt.supershell=never -Dsbt.version=1.3.0-M2 "logJVM/testOnly *ResourceTest"                                                                                                                                     
Getting org.scala-sbt sbt 1.3.0-M2  (this may take some time)...
:: retrieving :: org.scala-sbt#boot-app
        confs: [default]
        80 artifacts copied, 0 already retrieved (29549kB/218ms)
[info] Loading settings for project global-plugins from idea.sbt,global.sbt ...
[info] Loading global plugins from /Users/ethanatkins/.sbt/1.0/plugins
[info] Loading settings for project airframe-build from plugin.sbt ...
[info] Loading project definition from /Users/ethanatkins/work/oss/sbt/community/airframe/project
[warn] There may be incompatibilities among your library dependencies; run 'evicted' to see detailed eviction warnings.
[info] Loading settings for project root from build.sbt ...
[info] Resolving key references (32254 settings) ...
[info] Set current project to airframe-root (in build file:/Users/ethanatkins/work/oss/sbt/community/airframe/)
[info] ResourceTest:
[info] Resource
[info] - should find files from the current class loader
[info] - should find resources from jar files *** FAILED ***
[info]   0 was not greater than 0 (ResourceTest.scala:41)
[info] - should find classes of specific types *** FAILED ***
[info]   0 was not greater than 0 (ResourceTest.scala:49)
[info] ResourceReader trait
[info] - should find files using the context class
[info] Run completed in 509 milliseconds.
[info] Total number of tests run: 4
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 2, failed 2, canceled 0, ignored 0, pending 0
[info] *** 2 TESTS FAILED ***
[error] Failed tests:
[error]         wvlet.log.io.ResourceTest
[error] (logJVM / Test / testOnly) sbt.TestsFailedException: Tests unsuccessful
[error] Total time: 3 s, completed Apr 2, 2019 5:00:51 PM
ethanatkins@Ethans-MacBook-ProZ:~/work/oss/sbt/community/airframe$ sbt8 -Dsbt.supershell=never -Dsbt.version=1.3.0-meta-0 "logJVM/testOnly *ResourceTest"                                                                                                                                 
Getting org.scala-sbt sbt 1.3.0-meta-0  (this may take some time)...
:: retrieving :: org.scala-sbt#boot-app
        confs: [default]
        80 artifacts copied, 0 already retrieved (29706kB/149ms)
[info] Loading settings for project global-plugins from idea.sbt,global.sbt ...
[info] Loading global plugins from /Users/ethanatkins/.sbt/1.0/plugins
[info] Loading settings for project airframe-build from plugin.sbt ...
[info] Loading project definition from /Users/ethanatkins/work/oss/sbt/community/airframe/project
[warn] There may be incompatibilities among your library dependencies; run 'evicted' to see detailed eviction warnings.
/Users/ethanatkins/work/oss/sbt/community/airframe/build.sbt:251: warning: value watchSources in object Keys is deprecated (since 1.3.0): WatchSource has been replaced by Glob. To add file triggers to a task with key: Key, set `Key / watchTriggers := Seq[Glob](...)`.               
      watchSources += new sbt.internal.io.Source(
      ^
[info] Loading settings for project root from build.sbt ...
[info] Resolving key references (32319 settings) ...
[info] Set current project to airframe-root (in build file:/Users/ethanatkins/work/oss/sbt/community/airframe/)
[info] ResourceTest:
[info] Resource
[info] - should find files from the current class loader
[info] - should find resources from jar files
[info] - should find classes of specific types
[info] ResourceReader trait
[info] - should find files using the context class
[info] Run completed in 681 milliseconds.
[info] Total number of tests run: 4
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 4, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 4 s, completed Apr 2, 2019 5:01:39 PM

1reaction

eatkinscommented, Apr 1, 2019

Ok, cool. I didn’t fully understand the use case. My point is simply that there is nothing in the sbt spec that says that run or test provide any specific URLClassLoader implementation so you are relying on undefined behavior. As long as we can agree on that point (or agree to disagree), I think we can move on.

I’m not saying you’re wrong. I am suggesting that if a URLClassLoader with specific semantics is required then it would be best practice to actually manage your classloaders manually and not rely on what sbt provides by default. Then you will not be impacted if sbt (or any other build tool) changes the implementation out from underneath you.

Again, I am planning to fix the current airframe build before sbt 1.3.0.