[MNG-5104] Enforcing build order...

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Incomplete
• Affects Version/s: 2.2.1
• Component/s: Bootstrap & Build, Reactor and Workspace
• Environment: Linux AMD64
• Assignee: Unassigned
• Reporter: Ancoron Luciferis
• Created: 24/May/11 18:30
• Updated: 22/Jan/14 20:32
• Resolved: 22/Jan/14 20:32

Description

Currently, building multi-module aka. reactor projects is working, but does not help the developers to ensure a certain level of isolation of their modules.

E.g. imagine the following project tree:

• <root>
  • Component A
    • A.api
    • A.jpa
    • A.ejb (depends on A.api, A.jpa)
  • Component B
    • B.api
    • B.jpa
    • B.ejb (depends on B.api, B.jpa, A.api)
  • Component C
    • C.api
    • C.jpa
    • C.ejb (depends on C.api, C.jpa, A.api)

...and all things are just fine.

Now, some developer comes in, not fully aware of the "big picture", producing something like this:

• <root>
  • Component A
    • A.api
    • A.jpa (depends on B.jpa)
    • A.ejb (depends on A.api, A.jpa)
  • Component B
    • B.api
    • B.jpa
    • B.ejb (depends on B.api, B.jpa, A.api, C.ejb)
  • Component C
    • C.api
    • C.jpa
    • C.ejb (depends on C.api, C.jpa, A.api)

...so in an old-school build with tools like Ant this would fail to build as the build order is clear and strict, according to best-practices. Not so with Maven. In the first case Maven might (although unlikely and yet to be seen) come up with a clear build order like this:

1. <root>
2. Component A
3. A.api
4. A.jpa
5. A.ejb
6. Component B
7. B.api
8. B.jpa
9. B.ejb
10. Component C
11. C.api
12. C.jpa
13. C.ejb

...however, in the second case Maven will not fail to build and instead come up with something like this:

1. <root>
2. Component A
3. A.api
4. Component B
5. B.jpa
6. A.jpa
7. A.ejb
8. B.api
9. Component C
10. C.api
11. C.jpa
12. C.ejb
13. B.ejb

All artifacts are build correctly, but it is no longer guaranteed that e.g. "Component A" could be used without "Component B", therefore introducing a requirement and eventually a lot of changes to the build-/tool-/test-chain.

So we would like to have an option to disable the Maven "magic" here and just stupidly build according to the <module> tags we've carefully written.