Move module list into pomless aggregators

.mvn/maven.config

@@ -1,3 +1,4 @@
 -T4
 -Dtycho.localArtifacts=ignore
 -Dtycho.version=5.0.2
+-Dtycho.pomless.parent=${maven.multiModuleProjectDirectory}

PomlessAggregator.adoc

@@ -0,0 +1,99 @@
+= Pomless aggregators with Tycho
+:toc: left
+:toclevels: 2
+:icons: font
+:source-highlighter: rouge
+
+== What this repository demonstrates
+
+Tycho's `tycho-build` extension can derive a Maven model for a bundle, feature, product or update site from the files that already describe it, so most modules here have no `pom.xml`.
+The same mechanism can also derive an *aggregator*, which is what this repository uses to keep the module list out of the root `pom.xml`.
+
+Two variants are shown:
+
+`build/pom.tycho`:: The reactor module list. The root `pom.xml` declares a single module, and the real list lives in a plain text file.
+`lsp/pom.tycho`:: A group of related bundles collected in their own folder, listed by an aggregator of their own.
+
+== How it works
+
+A folder containing a file named `pom.tycho` is turned into an aggregator with packaging `pom`.
+The artifactId is the folder name, and every non-comment line becomes a `<module>` entry.
+
+.build/pom.tycho
+[source]
+----
+# "#" comments and blank lines are ignored
+../com.vogella.ide.first
+../lsp
+----
+
+Because the lines are used verbatim, they may point outside the aggregator's own folder.
+That is what allows `build/` to reference bundles that sit at the repository root.
+
+The root `pom.xml` keeps everything else it needs to keep, and shrinks to:
+
+[source,xml]
+----
+<modules>
+  <module>build</module>
+</modules>
+----
+
+NOTE: A `pom.tycho` is only read in a folder that has no `pom.xml`.
+Where both exist the `pom.xml` always wins, so the root pom cannot source its own module list this way.
+That is why the indirection through `build/` is needed.
+
+=== Automatic detection
+
+If a folder is named `bundles`, `plugins`, `tests`, `features`, `sites`, `products` or `releng`, Tycho scans its subfolders and generates the module list without any file at all.
+The list of names is configurable with `-Dtycho.pomless.aggregator.names`.
+
+This repository deliberately uses an explicit `lsp/pom.tycho` instead, for two reasons.
+The folder name `lsp` says what the group is, and an explicit list keeps the ability to disable a single module by commenting out one line.
+Automatic detection always takes every subfolder it finds.
+
+TIP: Tycho writes its generated `pom.tycho` files with a `## tycho automatic module detection <uuid>` first line and deletes them when the JVM exits.
+A hand-written file simply must not start with that marker.
+
+== Required configuration
+
+Two settings make the nested layout work.
+
+..mvn/maven.config
+[source]
+----
+-Dtycho.pomless.parent=${maven.multiModuleProjectDirectory}
+----
+
+By default a pomless module looks for its parent in `..`.
+That holds for a bundle at the repository root, but not for one nested inside `lsp/`, which would look in `lsp/` and find nothing.
+Pointing the property at the directory that contains `.mvn` makes every pomless module resolve the root pom as its parent, whatever its depth.
+`maven.multiModuleProjectDirectory` is resolved by Maven itself, so the setting keeps working when the build is started from a subdirectory.
+
+The same property can be set per module, as `tycho.pomless.parent` in a bundle's `build.properties`, which takes precedence over the global default.
+
+.pom.xml
+[source,xml]
+----
+<file>${maven.multiModuleProjectDirectory}/target-platform/target-platform.target</file>
+----
+
+The target definition was previously referenced as `../target-platform/target-platform.target`.
+That path is resolved against each module's own directory, so it breaks for a module one level deeper.
+An absolute path avoids the problem for good.
+
+== Trade-offs
+
+The module list is no longer XML, comments are cheaper, and related bundles can be grouped without the root pom growing.
+Set against that, the list is no longer where a reader expects it, and `build/` exists only as an indirection.
+For a repository with a handful of modules that is a poor trade.
+It starts paying off at the scale of this one, where nearly every module is pomless already.
+
+== Building
+
+Nothing changes for the caller:
+
+[source,bash]
+----
+./mvnw clean verify
+----

build/pom.tycho

@@ -0,0 +1,46 @@
+# The reactor module list.
+#
+# Tycho's pomless build turns this file into an aggregator (packaging=pom,
+# artifactId "build"), so the root pom.xml only needs a single <module>build</module>
+# entry instead of one line per bundle. Paths are relative to this folder,
+# hence the "../" prefix for everything that lives at the repository root.
+#
+# "#" comments and blank lines are ignored, which makes temporarily disabling
+# a module a one-character edit.
+
+../com.vogella.ide.first
+../com.vogella.ide.feature
+../com.vogella.tasks.model
+../com.vogella.tasks.services
+../com.vogella.tasks.ui
+../com.vogella.ide.editor.tasks
+../com.vogella.contribute.parts
+../com.vogella.swt.widgets
+../com.vogella.tasks.events
+../com.vogella.eclipse.css
+
+../com.vogella.resources
+../com.vogella.adapters
+../com.vogella.tasks.extendedsupplier
+../com.vogella.preferences.page
+../com.vogella.ide.editor.gradle
+../com.vogella.ide.editor.asciidoc
+../com.vogella.ide.editor.shell
+../com.vogella.ide.debugtools
+
+# Language server example, grouped in its own folder with its own pom.tycho
+../lsp
+
+../z.ex.search
+../com.vogella.ide.iconreplacer
+../com.vogella.ide.parallelstart
+../com.vogella.json.validation
+
+# Tests
+../com.vogella.json.validation.tests
+# ../com.vogella.tasks.services.tests
+
+../updatesite
+
+# releng
+# ../com.vogella.ide.product

lsp/pom.tycho

@@ -0,0 +1,12 @@
+# Modules of the "lsp" aggregator.
+#
+# This file replaces an lsp/pom.xml. Tycho's pomless build reads it and
+# generates an aggregator with packaging=pom and artifactId "lsp" (the folder
+# name). One module per line, "#" comments and blank lines are ignored.
+#
+# An explicit list is required here because "lsp" is not one of the folder
+# names Tycho scans automatically (bundles, plugins, tests, features, sites,
+# products, releng).
+com.vogella.lsp.asciidoc.client
+com.vogella.lsp.asciidoc.server
+com.vogella.lsp.asciidoc.server.tests

pom.xml

@@ -89,7 +89,7 @@
         <version>${tycho.version}</version>
         <configuration>
           <target>
-            <file>../target-platform/target-platform.target</file>
+            <file>${maven.multiModuleProjectDirectory}/target-platform/target-platform.target</file>
           </target>
           <!-- Optional set the Java version your are using-->
           <executionEnvironment>JavaSE-25</executionEnvironment>
@@ -115,43 +115,7 @@
     </plugins>
   </build>
   <modules>
-    <module>com.vogella.ide.first</module>
-    <module>com.vogella.ide.feature</module>
-    <module>com.vogella.tasks.model</module>
-    <module>com.vogella.tasks.services</module>
-    <module>com.vogella.tasks.ui</module>
-    <module>com.vogella.ide.editor.tasks</module>
-    <module>com.vogella.contribute.parts</module>
-    <module>com.vogella.swt.widgets</module>
-    <module>com.vogella.tasks.events</module>
-    <module>com.vogella.eclipse.css</module>
-    <!---->
-    <module>com.vogella.resources</module>
-    <module>com.vogella.adapters</module>
-    <module>com.vogella.tasks.extendedsupplier</module>
-    <module>com.vogella.preferences.page</module>
-    <module>com.vogella.ide.editor.gradle</module>
-    <module>com.vogella.ide.editor.asciidoc</module>
-    <module>com.vogella.ide.editor.shell</module>
-    <module>com.vogella.ide.debugtools</module>
-    <module>com.vogella.lsp.asciidoc.client</module>
-    <module>com.vogella.lsp.asciidoc.server</module>
-    <module>com.vogella.lsp.asciidoc.server.tests</module>
-    <module>z.ex.search</module>
-    <module>com.vogella.ide.iconreplacer</module>
-    <module>com.vogella.ide.parallelstart</module>
-    <module>com.vogella.json.validation</module>
-
-    <!--Tests-->
-    <module>com.vogella.json.validation.tests</module>
-    <!--
-
-    <module>com.vogella.tasks.services.tests</module>
--->
-    <module>updatesite</module>
-    <!--releng-->
-    <!-- <module>com.vogella.ide.product</module> -->
-
-
+    <!-- The real module list lives in build/pom.tycho -->
+    <module>build</module>
   </modules>
 </project>