test(spring): Compile the Spring modules against their oldest Spring Boot version

Since the matrix stopped rewriting the catalog, the SDK only compiles
against the catalog's Spring Boot version, so nothing checked any more
that it compiles against the oldest version of each line. An unguarded
call to a newer API would only fail if a suite ran that code path.

The Spring Boot matrix plugin now registers compileJavaBoot<oldest> in
each of the six modules, compiling the main sources against a compile
classpath resolved for the line's oldest version. The oldest version's
aggregate depends on it, so the matrix workflows run it.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: runningcode

.cursor/rules/e2e_tests.mdc

@@ -76,6 +76,8 @@ it. Gradle runs the two in parallel.
   module once it's added to its workflow.
 - Suite code may only use APIs that exist in the oldest version of its line. Compiled against a
   newer one, a missing API fails at runtime with `NoSuchMethodError` or `NoClassDefFoundError`.
+- The oldest version's aggregate also compiles the module's main code against that version, e.g.
+  `compileJavaBoot3_2_12`, since nothing else checks that the SDK compiles against it.
 
 ## Gotchas
 

build-logic/src/main/kotlin/io/sentry/gradle/SpringBootMatrixPlugin.kt

@@ -6,6 +6,7 @@ import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.file.FileCollection
 import org.gradle.api.tasks.SourceSetContainer
+import org.gradle.api.tasks.compile.JavaCompile
 import org.gradle.api.tasks.testing.Test
 import org.gradle.language.base.plugins.LifecycleBasePlugin
 
@@ -30,6 +31,10 @@ abstract class SpringBootMatrixExtension @Inject constructor(private val project
    * `gradle/spring-boot-versions.json`, and `allIntegrationTestsBoot<line>` for all of them. The CI
    * workflows read the same file and run each version in its own job. A WAR module uses its Boot
    * module's line, because the Boot BOM decides its Spring version.
+   *
+   * The line's first version must be the oldest. The module's main code compiles against it in
+   * `compileJavaBoot<version>`, part of that version's aggregate, because the main compilation only
+   * proves the code compiles against the catalog's version.
    */
   fun versions(line: Int) {
     val file = project.layout.settingsDirectory.file("gradle/spring-boot-versions.json")
@@ -48,6 +53,22 @@ abstract class SpringBootMatrixExtension @Inject constructor(private val project
         group = LifecycleBasePlugin.VERIFICATION_GROUP
       }
     }
+
+    val oldest = versions.first()
+    val compileClasspath = classpath("main", oldest, compile = true)
+    val compileOldest =
+      project.tasks.register("compileJava${suffix(oldest)}", JavaCompile::class.java) {
+        description = "Compiles the main Java sources against Spring Boot $oldest."
+        group = LifecycleBasePlugin.VERIFICATION_GROUP
+        val compileJava = project.tasks.named("compileJava", JavaCompile::class.java).get()
+        source = sourceSet("main").java
+        classpath = compileClasspath
+        destinationDirectory.set(project.layout.buildDirectory.dir("classes/java/main${suffix(oldest)}"))
+        javaCompiler.set(compileJava.javaCompiler)
+        options.release.set(compileJava.options.release)
+        options.annotationProcessorPath = compileJava.options.annotationProcessorPath
+      }
+    project.tasks.named(aggregateName(oldest)) { dependsOn(compileOldest) }
   }
 
   /**
@@ -74,28 +95,29 @@ abstract class SpringBootMatrixExtension @Inject constructor(private val project
   }
 
   /** [sourceSet]'s output and runtime dependencies, with Spring Boot at [version]. */
-  fun runtimeClasspath(sourceSet: String, version: String): FileCollection {
+  fun runtimeClasspath(sourceSet: String, version: String): FileCollection =
+    sourceSet(sourceSet).output + classpath(sourceSet, version, compile = false)
+
+  /** [sourceSet]'s compile or runtime classpath dependencies, with Spring Boot at [version]. */
+  private fun classpath(sourceSet: String, version: String, compile: Boolean): FileCollection {
     val sources = sourceSet(sourceSet)
-    val name = "$sourceSet${suffix(version)}RuntimeClasspath"
+    val base =
+      if (compile) sources.compileClasspathConfigurationName
+      else sources.runtimeClasspathConfigurationName
+    val name = "$sourceSet${suffix(version)}${if (compile) "Compile" else "Runtime"}Classpath"
     val configurations = project.configurations
-    val dependencies =
-      configurations.findByName(name)
-        ?: configurations.create(name) {
-          isCanBeConsumed = false
-          extendsFrom(
-            configurations.getByName(sources.implementationConfigurationName),
-            configurations.getByName(sources.runtimeOnlyConfigurationName),
-          )
-          attributes.addAllLater(
-            configurations.getByName(sources.runtimeClasspathConfigurationName).attributes
-          )
-          // What setting the version in the catalog does: every Spring Boot artifact, the BOM
-          // included, is in this group. Libraries pinned to their own version still win conflicts.
-          resolutionStrategy.eachDependency {
-            if (requested.group == "org.springframework.boot") useVersion(version)
-          }
+    return configurations.findByName(name)
+      ?: configurations.create(name) {
+        isCanBeConsumed = false
+        val baseConfiguration = configurations.getByName(base)
+        extendsFrom(*baseConfiguration.extendsFrom.toTypedArray())
+        attributes.addAllLater(baseConfiguration.attributes)
+        // What setting the version in the catalog does: every Spring Boot artifact, the BOM
+        // included, is in this group. Libraries pinned to their own version still win conflicts.
+        resolutionStrategy.eachDependency {
+          if (requested.group == "org.springframework.boot") useVersion(version)
         }
-    return sources.output + dependencies
+      }
   }
 
   private fun sourceSet(name: String) =