This document discusses module repositories in Ceylon, including: - Modules are now a fundamental part of the language design in Ceylon - The Ceylon Module Repository (CMR) is used by the typechecker and runtime to locate dependent modules - Modules are compiled to a local repository and can then be shared globally using repositories like the Herd module repository - Maven repositories can be used but sometimes have invalid metadata that requires workarounds - The CMR, runtime, and other Ceylon components are implemented as modules themselves.

1. Module repositories
Aleš Justin, Red Hat

2. Modules?
• History
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Java SDK monolith
JSR-277, JSR-294, …
OSGi
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• Should be part of the language!
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Well, you cannot ignore legacy
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A ton of cool Java libs, …
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• It’s all about modules in Ceylon!
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(at least that’s what Stéphane tells me ;-)

3. Compiling the app?
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Something needs to know how to *find* dependent modules
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Typechecker “talks” to Ceylon Module Repository (CMR)
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Once an app module is compiled, it goes into local module
repo → *ready* to be used by other modules
!
But how do we share it “globally”?

4. Running the app?
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Directly — MyApp::main(String… args) ?
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BOOM!! … as nobody knows how to *load* dependent modules
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Custom “Runtime”
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JBoss Modules based (WildFly AS proven; p2p classloading)
“Talks” to CMR to lookup modules
Lazy initialisation; build minimal transient closure of dependency info

5. More module lookups
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• Sources, module list view and compiling
JavaScript backend
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IDE
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Lookup .js files

6. Module lookup
• <name,version> → module or <null>
• No range lookup
• Set of repositories
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Local
Remote
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File system
Maven
WebDav
Herd
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Transferring module’ bytecode bits and *dependency info*
• Type of repository
• Remote → Local

7. Dependency info
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• import org.acme.poke “1.0”
Maven
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• From pom.xml / via Aether
• JBoss Modules
• module.xml
Custom jar
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• module.properties
• OSGi (wip)
Native

8. Maven trouble?
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Some Maven pom.xml files are “invalid”
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Transitive dependencies / flat classpath
2nd level dep used directly
!
• Fix?
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Current workaround = overrides.xml
Add
Remove
Replace
Any better idea?

9. Repositories configuration
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• Distrib, Project, User, Cache, Herd, …
Add your own
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• —rep <repo config>
Customise things in .ceylon/config
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Default

10. Module sharing?
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Herd (http://modules.ceylon-lang.org/)
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Upload your modules
Upload permission
Dependency pre-check
Integrity validation check
Set-up your own Herd
!
• Query for modules
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If supported by repository type

11. Misc
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• Can be used in the app; but not encouraged
Language and JDK are added by default
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• Yes, even JDK is a module (actually multiple modules)
Logging module(s) have special treatment
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• So all logs end-up at the same place — JBoss LogManager
CMR is pluggable — RepositoryBuilder
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CMR, Runtime, Typechecker, … are also all modules
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Impl your own Repository

12. Thanks!
!
ajustin@redhat.com
Q&A anytime