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Cache projectsUsingPlugin to fix O(N²) reactor scan #427

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Cache projectsUsingPlugin to fix O(N²) reactor scan #427

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24 changes: 22 additions & 2 deletions src/main/java/org/apache/maven/plugins/install/InstallMojo.java
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Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,7 @@ private enum State {
}

private static final String INSTALL_PROCESSED_MARKER = InstallMojo.class.getName() + ".processed";
private static final String PROJECTS_USING_PLUGIN_KEY = InstallMojo.class.getName() + ".projectsUsingPlugin";

public InstallMojo() {}

Expand All @@ -120,6 +121,26 @@ private boolean hasState(Project project) {
return pluginContext.containsKey(INSTALL_PROCESSED_MARKER);
}

/**
* Returns the list of reactor projects that have this plugin configured, cached on first call.
* The list is invariant during a build and is stored in the current project's plugin
* context to avoid recomputing it on every module invocation (O(N) total instead of O(N²)).
*/
@SuppressWarnings("unchecked")
private List<Project> getProjectsUsingPlugin() {
List<Project> allProjects = session.getProjects();
if (allProjects.isEmpty()) {
return List.of();
}
Map<String, Object> ctx = session.getPluginContext(allProjects.get(0));
List<Project> cached = (List<Project>) ctx.get(PROJECTS_USING_PLUGIN_KEY);
if (cached == null) {

@mfriedenhagen mfriedenhagen Aug 6, 2026

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Does this work properly when Maven processes modules in parallel? I do not see any locking.

cached = allProjects.stream().filter(this::usingPlugin).collect(Collectors.toList());
ctx.put(PROJECTS_USING_PLUGIN_KEY, cached);
}
return cached;
}

private boolean usingPlugin(Project project) {
Plugin plugin = project.getBuild().getPluginsAsMap().get("org.apache.maven.plugins:maven-install-plugin");
return plugin != null
Expand All @@ -144,8 +165,7 @@ public void execute() {
}
}

List<Project> projectsUsingPlugin =
session.getProjects().stream().filter(this::usingPlugin).collect(Collectors.toList());
List<Project> projectsUsingPlugin = getProjectsUsingPlugin();
if (allProjectsMarked(projectsUsingPlugin)) {
for (Project reactorProject : projectsUsingPlugin) {
State state = getState(reactorProject);
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