How to get an eclipse-based dependency (p2 or mavenCentral)?

[frankbenoit]

Hi Ned,

I find it difficult to understand how to use Goomph.

Creating a project using SWT/JFace seems to work:

eclipseMavenCentral {
    release '4.13.0', {
        implementation 'org.eclipse.swt'
        implementation 'org.eclipse.jface'
        useNativesForRunningPlatform()
    }
}

Next I want to use SWTBot, from the update site https://download.eclipse.org/technology/swtbot/releases/latest/

• 'org.eclipse.swtbot.go'
• 'org.eclipse.swtbot.junit4_x'
• 'org.eclipse.swtbot.swt.finder'

How can i make those bundles available?

Frank

[nedtwigg]

I find it difficult to understand how to use Goomph.

Sorry :( Ignoring the "IDE-generation" part, and focusing on just on the "build an eclipse-based application" part, here is a high-level overview:

Algorithm for finding eclipse-based dependencies

A lot of eclipse projects only publish to their own p2 repository. Some publish to both p2 and mavenCentral.

• Search for your library here: https://search.maven.org/
• If it shows up, you can get it directly from mavenCentral if you want
  • If the groupId is one of these, then you can use our eclipseMavenCentral to specify the version in terms of the eclipse release (e.g. 4.7.2) rather than the long per-jar naming format that most eclipse projects use
• if it doesn't show up, then you have no choice but to use p2asmaven.

Details

Consuming p2 dependencies

We built Goomph because we found it difficult to use p2. So we wrapped up p2 with p2asmaven, which makes it possible to run the p2 standalone application and stuff the results into a plain-old maven repository. This will always work with any p2 repository, but it's just a wrapper. That means that there are a lot of performance and "debuggability" problems that we can't solve. For example, when a p2 mirror operation hangs, the answer lies deep inside p2 internals - we're just shelling out to it, not much we can do.

Cross-published p2 / mavenCentral dependencies

Starting with eclipse 4.6.2, when eclipse published a new release to their official p2 repository, they also published to mavenCentral. However, this is only for the "core" libraries - SWT, OSGi/Equinox, JDT, PDE. The eclipseMavenCentral plugin just lets you download those dependencies using 4.7.0 as your version, rather than the long unique-to-each jar version that they have in maven central. SWTBot is not part of this core, so you can't use eclipseMavenCentral to do it.

Building RCP applications

We used to ship DiffPlug as an OSGi/RCP application. We opensourced the code that we used to do this as PdeBuildTask/PdeAntTask. Over time, we found that OSGi/RCP were adding more maintenance burden than they were worth, and we have stopped using them. So they still work for older eclipse versions, and I don't know why they wouldn't work for newer eclipse versions too. We're happy to take PRs to update them, and its fine to post bugs documenting bugs without a solution, but nobody at DiffPlug is actively working on this.

[frankbenoit]

Hi Ned,

thanks for you reply.

I don't yet understand how I can explore the available APIs. Perhaps this is a general problem for me understanding Gradle plugins.
Now i guessed, perhaps it takes repo, and really that worked.
But how am I able to find this in the docs? As Groovy/Eclipse gives my no hints via autocomplete proposals, i am fully depending on the written docs.

p2AsMaven {
    group 'org.eclipse.swtbot', {
        repo 'http://download.eclipse.org/technology/swtbot/releases/latest'
        iu 'org.eclipse.swtbot.go'
        iu 'org.eclipse.swtbot.junit4_x'
        iu 'org.eclipse.swtbot.swt.finder'
    }
}
eclipseMavenCentral {
    release '4.13.0', {
        implementation 'org.eclipse.swt'
        implementation 'org.eclipse.jface'
        useNativesForRunningPlatform()
    }
}

Now i see it accessing the repos, but failing to resolve:

[p2.mirror] Problems resolving provisioning plan.
[p2.mirror] Unable to satisfy dependency from org.eclipse.swtbot.junit4_x 2.8.0.201906121535 to package org.eclipse.swt.widgets 0.0.0.
[p2.mirror] Unable to satisfy dependency from org.eclipse.swtbot.junit4_x 2.8.0.201906121535 to package org.junit 4.12.0.
[p2.mirror] Unable to satisfy dependency from org.eclipse.swtbot.junit4_x 2.8.0.201906121535 to package org.junit.runner 4.12.0.
...

How can i make p2AsMaven aware:
package org.junit.runner 4.12.0 shall be found in junit:junit:4.12 ?
package org.eclipse.swt.widgets 0.0.0 shall be found in ???:org.eclipse.swt ?

Frank

[hacki11]

Just found out about this plugin. Did i understand the following correctly:
It is not possible to make PdeBuildTask aware of that the base directory for the target (p2) is handled by eclipseMavenCentral instead of p2AsMaven?

Do i have to mirror the p2 repository and have the eclipseMavenCentral redundantly?

[nedtwigg]

I don't yet understand how I can explore the available APIs.

The README has (broken) links to the javadoc, but changing 3.18.1 to 3.18.0 in the URL will fix them. The broken links will get fixed the next time I work on goomph (next eclipse release). In the meantime:

https://diffplug.github.io/goomph/javadoc/3.18.0/com/diffplug/gradle/p2/AsMavenPlugin.html

How can i make p2AsMaven aware

You'll have to get p2 to ignore missing dependencies. We're just shelling out to this, so setting followStrict, true in the slicing options should work.

p2AsMaven doesn't encode p2 dependencies into maven dependencies, so there won't be any problem that the p2 groupId is different than the maven groupId.

@hacki11 please open a new issue if you want to discuss further, but probably you should not use eclipseMavenCentral if you also want to use PdeBuildTask.

[frankbenoit]

Hi

sorry for again asking....
Now I have this:

buildscript {
	repositories {
		jcenter()
		mavenCentral()
	}
	dependencies {
		classpath 'com.diffplug.gradle:goomph:3.18.1'
	}
} 

apply plugin: 'com.diffplug.gradle.eclipse.mavencentral'
apply plugin: 'com.diffplug.gradle.p2.asmaven'
apply plugin: 'java'

repositories {
    jcenter()
	mavenCentral()
}

p2AsMaven {
    group 'org.eclipse.swtbot', {
        repo 'http://download.eclipse.org/technology/swtbot/releases/latest'
        iu 'org.eclipse.swtbot.go'
        iu 'org.eclipse.swtbot.junit4_x'
        iu 'org.eclipse.swtbot.swt.finder'
        slicingOption 'followStrict', 'true'
    }
}

eclipseMavenCentral {
    release '4.13.0', {
        implementation 'org.eclipse.swt'
        implementation 'org.eclipse.jface'
        useNativesForRunningPlatform()
    }
}

dependencies {
    implementation 'org.eclipse.swtbot:org.eclipse.swtbot.go'
    implementation 'org.eclipse.swtbot:org.eclipse.swtbot.junit4_x:+'
    implementation 'org.eclipse.swtbot:org.eclipse.swtbot.swt.finder:+'

    testImplementation 'junit:junit:4.12'
    testImplementation 'org.junit.jupiter:junit-jupiter:5.5.2'
	testRuntimeOnly    'org.junit.vintage:junit-vintage-engine:5.5.2'
}

test {
	useJUnitPlatform {
	}
	testLogging {
		events("passed", "skipped", "failed")
	}
}

The previous complaints are gone with the slicing option.

Now it tells me, it cannot resolve the deps:

Could not resolve: org.eclipse.swtbot:org.eclipse.swtbot.go
Could not resolve: org.eclipse.swtbot:org.eclipse.swtbot.junit4_x:+
Could not resolve: org.eclipse.swtbot:org.eclipse.swtbot.swt.finder:+

Frank

[frankbenoit]

Hi

now i learned, that dots in the groupId are not good, as they are seen as subdirs and p2asmaven does not do those.
I changed org.eclipse.swtbot to be swtbot only.

Execution failed for task ':compileJava'.
> Could not resolve all files for configuration ':compileClasspath'.
   > Could not find any matches for swtbot:org.eclipse.swtbot.go:+ as no versions of swtbot:org.eclipse.swtbot.go are available.
     Searched in the following locations:
       - https://jcenter.bintray.com/swtbot/org.eclipse.swtbot.go/maven-metadata.xml
       - https://repo.maven.apache.org/maven2/swtbot/org.eclipse.swtbot.go/maven-metadata.xml
       - file:/C:/prj/build/p2asmaven/maven/swtbot/org.eclipse.swtbot.go/maven-metadata.xml
       - file:/C:/prj/build/p2asmaven/maven/swtbot/org.eclipse.swtbot.go/2.8.0.201906121535/org.eclipse.swtbot.go-2.8.0.201906121535.pom

But the file c:\prj\build\p2asmaven\maven\swtbot\org.eclipse.swtbot.go\maven-metadata.xml is existing and lists the available version.

What else can i check?

Frank

[nedtwigg]

Are you using Gradle 6? There is a known bug with Gradle 6 and p2asmaven. Downgrading to gradle 5.6.4 will fix it.

[frankbenoit]

Hi

yes, that's finally it.
Back to 5.6.2 made it work.

Thanks!

Frank

[liblit]

@frankbenoit, that “known bug” now has a suggested fix if you prefer to move back to Gradle 6.

[frankbenoit]

@liblit
Thanks for hint.

I tried to get this work:

repositories {
    jcenter()
	mavenCentral()
	maven {
            repo 'http://download.eclipse.org/technology/swtbot/releases/latest'
	    metadataSources {
	        mavenPom()
	        artifact()
	    }
	}
}

p2AsMaven {
    group 'swtbot', {
        repo 'http://download.eclipse.org/technology/swtbot/releases/latest'
        iu 'org.eclipse.swtbot.go'
        iu 'org.eclipse.swtbot.junit4_x'
        iu 'org.eclipse.swtbot.swt.finder'
        iu 'org.apache.log4j'
        slicingOption 'followStrict', 'true'
    }
}

But this gives:

* What went wrong:
You must specify a URL for a Maven repository.

Any idea how to apply the workaround using p2AsMaven?

Frank

[liblit]

@frankbenoit asked:

Any idea how to apply the workaround using p2AsMaven?

I was able to stop using p2AsMaven entirely. Unfortunately that means I have not used the suggested fix myself, so I have nothing more to suggest.

[nedtwigg]

I think it will require goomph to implement the workaround, which I plan to do soon. Watch #106 for status updates.