Fix platform constraint processing to avoid accidental exclude

Previously, a constraint in a platform that applied to a transitive
dependency of the platform would prevent subsequent processing of
that dependency. This resulted in the dependency being
unintentionally excluded.

This commit updates the configuring of exclusions to only track a
dependency is seen when it's an actual dependency and not a
constraint.

Closes gh-368

src/main/java/io/spring/gradle/dependencymanagement/internal/ExclusionConfiguringAction.java

@@ -155,7 +155,7 @@ private void handleResolvedDependency(ResolvedDependencyResult dependency, Node
 			Map<String, Exclusions> pomExclusionsById, LinkedList<Node> queue, Set<ResolvedComponentResult> seen) {
 		ResolvedComponentResult child = dependency.getSelected();
 		String childId = getId(child);
-		if (!node.excluded(childId) && seen.add(child) && !dependency.isConstraint()) {
+		if (!node.excluded(childId) && !dependency.isConstraint() && seen.add(child)) {
 			queue.add(new Node(child, childId, getChildExclusions(node, childId, pomExclusionsById)));
 		}
 	}

src/test/java/io/spring/gradle/dependencymanagement/DependencyManagementPluginIntegrationTests.java

@@ -516,6 +516,14 @@ void dependenciesDeclaredInAPlatformAreNotAccidentallyExcluded() {
 		assertThat(readLines("resolved.txt")).containsExactly("spring-core-5.3.27.jar", "spring-jcl-5.3.27.jar");
 	}
 
+	@Test
+	void platformConstrainingATransitiveDependencyDoesNotAccidentallyExcludeThatDependency() {
+		this.gradleBuild.runner().withArguments("resolve").build();
+		assertThat(readLines("resolved.txt")).containsExactly("okhttp-4.11.0.jar", "okio-jvm-3.6.0.jar",
+				"kotlin-stdlib-jdk8-1.9.10.jar", "kotlin-stdlib-jdk7-1.9.10.jar", "kotlin-stdlib-1.9.10.jar",
+				"kotlin-stdlib-common-1.9.10.jar", "annotations-13.0.jar");
+	}
+
 	private void writeLines(Path path, String... lines) {
 		try {
 			Path resolvedPath = this.gradleBuild.runner().getProjectDir().toPath().resolve(path);

src/test/resources/io/spring/gradle/dependencymanagement/DMPIT/platformConstrainingATransitiveDependencyDoesNotAccidentallyExcludeThatDependency.gradle

@@ -0,0 +1,24 @@
+plugins {
+	id "java"
+	id "io.spring.dependency-management"
+}
+
+repositories {
+	maven {
+		url file("maven-repo")
+	}
+	mavenCentral()
+}
+
+dependencies {
+	implementation(platform("test:platform-with-constrained-transitive-dependency:1.0"))
+}
+
+tasks.register("resolve") {
+	doFirst {
+		def files = project.configurations.compileClasspath.resolve()
+		def output = new File("${buildDir}/resolved.txt")
+		output.parentFile.mkdirs()
+		files.collect { it.name }.each { output << "${it}\n" }
+	}
+}

src/test/resources/maven-repo/test/platform-with-constrained-transitive-dependency/1.0/platform-with-constrained-transitive-dependency-1.0.module

@@ -0,0 +1,76 @@
+{
+  "formatVersion": "1.1",
+  "component": {
+    "group": "test",
+    "module": "platform-with-constrained-transitive-dependency",
+    "version": "1.0",
+    "attributes": {
+      "org.gradle.status": "release"
+    }
+  },
+  "createdBy": {
+    "gradle": {
+      "version": "8.4"
+    }
+  },
+  "variants": [
+    {
+      "name": "apiElements",
+      "attributes": {
+        "org.gradle.category": "platform",
+        "org.gradle.usage": "java-api"
+      },
+      "dependencies": [
+        {
+          "group": "com.squareup.okhttp3",
+          "module": "okhttp",
+          "version": {
+            "requires": "4.11.0"
+          }
+        }
+      ],
+      "dependencyConstraints": [
+        {
+          "group": "com.squareup.okio",
+          "module": "okio",
+          "version": {
+            "requires": "3.6.0",
+            "prefers": "latest.release",
+            "rejects": [
+              "3.2.0"
+            ]
+          }
+        }
+      ]
+    },
+    {
+      "name": "runtimeElements",
+      "attributes": {
+        "org.gradle.category": "platform",
+        "org.gradle.usage": "java-runtime"
+      },
+      "dependencies": [
+        {
+          "group": "com.squareup.okhttp3",
+          "module": "okhttp",
+          "version": {
+            "requires": "4.11.0"
+          }
+        }
+      ],
+      "dependencyConstraints": [
+        {
+          "group": "com.squareup.okio",
+          "module": "okio",
+          "version": {
+            "requires": "3.6.0",
+            "prefers": "latest.release",
+            "rejects": [
+              "3.2.0"
+            ]
+          }
+        }
+      ]
+    }
+  ]
+}

src/test/resources/maven-repo/test/platform-with-constrained-transitive-dependency/1.0/platform-with-constrained-transitive-dependency-1.0.pom

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <!-- This module was also published with a richer model, Gradle metadata,  -->
+  <!-- which should be used instead. Do not delete the following line which  -->
+  <!-- is to indicate to Gradle or any Gradle module metadata file consumer  -->
+  <!-- that they should prefer consuming it instead. -->
+  <!-- do_not_remove: published-with-gradle-metadata -->
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>test</groupId>
+  <artifactId>platform-with-constrained-transitive-dependency</artifactId>
+  <version>1.0</version>
+  <packaging>pom</packaging>
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>com.squareup.okio</groupId>
+        <artifactId>okio</artifactId>
+        <version>3.6.0</version>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+  <dependencies>
+    <dependency>
+      <groupId>com.squareup.okhttp3</groupId>
+      <artifactId>okhttp</artifactId>
+      <version>4.11.0</version>
+      <scope>compile</scope>
+    </dependency>
+  </dependencies>
+</project>