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Latest revision as of 04:36, 6 November 2019

Tycho Pomless Build Extension

Tycho is used to building Eclipse plug-ins, features, update sites, RCP applications and OSGi bundles with Maven. Maven itself requires some maven-related meta-data like artifact/group id, versions plugins to use an packaging types. Most of that meta-data is already available in the various files (MANIFEST.MF, feature.xml, product-file and so on) and actually Tycho requires that these metadata is synchronized in some extend, for example the pom.xml version must always match the MANIFEST.MF version. This leads to duplication of information and frustration of developers normaly using the PDE-IDE for development as they must create "useless" pom.xml files and keep things in sync, builds fail late because inconsistencies are only detected when the actual bundle is build.

Thats where the Tycho Pomless Build Extension can help to dramatically reduce the required configuration overhead, as all the boiler-plate xml-code could be generated automatically if you want to follow (and accept) some common patterns of deriving maven coordinates from OSGi-Artifacts.

Enabling pomless for your build

To enable pomless builds, create a folder named .mvn in the root of your build-tree and inside this folder a file named 'extensions.xml' with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<extensions>
 <extension>
   <groupId>org.eclipse.tycho.extras</groupId>
   <artifactId>tycho-pomless</artifactId>
   <version>1.5.1</version>
 </extension>
</extensions>

You probably want to check if a newer version is available as mentioned here in the example. Due to the nature of a build-extension you can't use properties from maven files, but System-properties if desired to specify the version actually used. From now on you can omit pom.xml files for the following cases.

general assumptions of tycho pomless

  • if there is a pom.xml in the folder, tycho pomless simply do nothing so you always have the choice to override tycho-pomless if needed
  • the group id is always inherited from the parent, this can't be overridden currently see https://github.com/takari/polyglot-maven/issues/193
  • the parent is always assumed to be in the default location (../pom.xml), you can override this see section 'Advanced parent pom configurations'
  • even though you can choose the build structure as you like, it is recommended to follow the Tycho/pomless/Structured Build approach as you can then benefit from the simplest configuration

Define target platform configuration pomless

You can define your target as you like according to https://wiki.eclipse.org/Tycho/Target_Platform If you are using a target file you can build that pomless if you follow these rules

  • either there is only one target file in the folder
  • or the target to use is named like the folder

Tycho pomless will the generate the following maven coordinates for this: version: inherited from the parent artifactId: name of used target file without the .target extension name: name of the target

Structured Build: In a structured build you would locate the target under releng/<desired-artifact-id>/<desired-artifact-id>.product

Special considerations: Placing target files into bundles/features is possible but will likely confuse tycho-pomless, it is recommended that you place the target into a plain project (Java/Maven/... is not required)

Building bundles/plugins pomless

If a folder contains a folder META-INF with a file MANIFEST.MF tycho-pomless considers this as a plugin folder (see next section for the special case of test bundles) and will generate the following maven-coordinates for you:

  • version: version specified in manifest
  • artifactId: bundle-symbolic name specified in manifest
  • name: name of the bundle specified in manifest taking the default localization into account if given

Structured Build: In a structured build you would locate bundles under bundles/<bsn>

test-bundles

A special case are bundles named .test or .tests in the end or those with a special property in build.properties, as those are considered test bundles and executed as eclipse-tests. You can control this behavior with the following property in build.properties:

tycho.pomless.testbundle=true/false

to either force the detection as a test bundle or to deny it to be detect as a test bundle

Currently it is not possible to configure this more, this is tracked in https://bugs.eclipse.org/bugs/show_bug.cgi?id=552370

Structured Build: In a structured build you would locate bundles under tests/<bsn>

Building features pomless

If a folder contains a feature.xml tycho-pomless assumes this is a feature project and will generate the following maven-coordinates for you:

  • version: version specified in manifest
  • artifactId: id of feature
  • name: name of the feature taking the default localization into account if given

Building products/update-sites pomless

Products and Updatesite both use eclipse-repository packaging type and are thus handled together

Updatesites

If a folder contains a category.xml tycho-pomless assumes this is an updatesite project and will generate the following maven-coordinates for you:

  • version: inherited from parent
  • artifactId: <name of folder>.eclipse-repository
  • name: <name of folder>.eclipse-repository

Structured Build: In a structured build you would locate updatesites under sites/<desired artifactId prefix>

Products

If a folder contains a *.product file tycho-pomless assumes this is a product project and will generate the following maven-coordinates for you:

  • version: version of product
  • artifactId: id of product
  • name: name of product

Structured Build: In a structured build you would locate products under products/<product-id>

Special considerations: Placing product/category.xml files into bundles/features is possible but will likely confuse tycho-pomless, it is recommended that you place the product into a plain project (Java/Maven/... is not required) and don't mix them. It is also possible to place many products into one directory in that case tycho will select an arbitrary one depending on your file-system.

pomless aggregation of modules

if you name a folder bundles, plugins, tests, features, sites, products or releng and it contains sub-folders that are either pom-based or pomless modules it assumes that this is an "aggregation" folder and will generate a pom file that lists all those as modules with the following maven-coordinates:

  • version: inherited from parent
  • groupid: <name of the folder>
  • modules: all valid sub-folder-modules

Effectively you now has toolset on our hands to build full PDE/Plugin artifact source with just one single pom.xml and in we are even investigating ways how we even can omit that when using structured builds.

The root-pom then might looks like this (of course it also works if you only use bundles and features for example):

<project>
  .... list all your favorite maven config here like tycho versions and plugin configuration ...
 <modules>
  <module>releng/my-target-for-pomless</module>
  <module>bundles/</module>
  <module>features/</module>
  <module>tests/</module>
  <module>sites/</module>
  <module>products/</module>
 </module>
</project>


Advanced parent pom configurations

You can, to some extend configure how tycho tries to inferring the parent:

  • define a system-property tycho.pomless.parent (defaults to "..") that configures the global default for searching parent poms (similar to tycho.localArtifacts this can't be configured in pom directly because of the early phase this is required)
  • you can define tycho.pomless.parent inside build.properties of individual bundle/fragment

If you are using the pomless aggregation of modules you can reference the generated parent the following way:

<parent>
 <groupId>...</groupId>
 <artifactId>...</artifactId>
 <version>...</version>
 <relativePath>../pom.tycho</relativePath>
</parent>

FAQ

Why Tycho Pomless? Shouldn't it be just Tycho?

Even though they closely relate to each other, tycho-pomless is, contrary to Tycho, a build-extension that can be used independent of Tycho (you can even use different versions of tycho-pomless and tycho) and only generates the necessary meta-data out of the RCP artifacts that is then used to actually do the build. Because of this, Tycho-pomless can't read configurations from maven poms (as these are not parsed at the time Tycho pomless kicks in), and only offers a subset of whole Tycho, but if you feel something is missing, feel free to open a bug here https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Tycho

What are all those files starting with a dot I see during the build?

Tycho pomless uses the the polyglot-maven build extension what uses the name of the replacement-pom and generates a file named '.polyglot.<name of replacement pom>'.

Each artifact (bundle, feature, product,/updatesite, target) has its own handler and uses the real marker file (e.g. the MANIFEST.MF, feature.xml, .product/category.xml, ...) as a replacement pom, so you will see different files starting with .polyglot.*, with two exceptions:

  • polyglot requires replacement poms to be a regular (existing!) file, not a folder, thus .META-INF_MANIFEST.MF is generated and deleted after the build finishes, sadly if you kill the build via Eclipse these files are not cleaned up due to https://bugs.eclipse.org/bugs/show_bug.cgi?id=38016
  • polyglot currently ignores all alternative files ending with .xml, (most notable feature.xml and category.xml), so also here a temporary file is created see https://github.com/takari/polyglot-maven/issues/192 for details
  • you might see another new file tycho.pom, that is generated when you use the automatic generation of module-aggregation files.

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