perf(core): Use build-time class availability (#5875)

* perf(core): Use build-time class availability

Consult class availability data injected by build tooling before falling back to reflection. Keep the map nullable so consumers without supporting tooling preserve current behavior.

Refs JAVA-654
Co-Authored-By: Codex <noreply@openai.com>

* ref(core): Make class availability package-private

Allow package-local tests to set class availability without reflection.

Refs LINEAR-JAVA-654

Co-Authored-By: Codex <noreply@openai.com>

---------

Co-authored-by: Codex <noreply@openai.com>

Author: romtsn

sentry/src/main/java/io/sentry/util/LoadClass.java

@@ -4,13 +4,17 @@
 import io.sentry.ILogger;
 import io.sentry.SentryLevel;
 import io.sentry.SentryOptions;
+import java.util.Map;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /** An Adapter for making Class.forName testable */
 @Open
 public class LoadClass {
 
+  // Populated by the Sentry Android Gradle plugin for class names it can resolve at build time.
+  static @Nullable Map<String, Boolean> classAvailability;
+
   /**
    * Loads and initializes a class via reflection. Use this when you intend to actually use the
    * class (e.g. instantiate it or invoke its methods). The returned class is fully initialized, so
@@ -57,6 +61,16 @@ public class LoadClass {
    * @return true if the class is on the classpath
    */
   public boolean isClassAvailable(final @NotNull String clazz, final @Nullable ILogger logger) {
+    final @Nullable Map<String, Boolean> availability = classAvailability;
+    if (availability != null) {
+      final @Nullable Boolean available = availability.get(clazz);
+      if (available != null) {
+        if (!available && logger != null) {
+          logger.log(SentryLevel.INFO, "Class not available: " + clazz);
+        }
+        return available;
+      }
+    }
     return loadClass(clazz, logger, false) != null;
   }
 

sentry/src/test/java/io/sentry/util/LoadClassTest.kt

@@ -1,12 +1,39 @@
 package io.sentry.util
 
+import com.google.common.truth.Truth.assertThat
 import kotlin.test.Test
 import kotlin.test.assertFalse
 import kotlin.test.assertNotNull
 import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
 class LoadClassTest {
+  @Test
+  fun `isClassAvailable uses known build-time results and reflects unknown classes`() {
+    LoadClass.classAvailability =
+      mapOf(
+        "io.sentry.SentryEvent" to false,
+        "io.sentry.ThisClassDoesNotExist" to true,
+      )
+
+    try {
+      val loadClass = LoadClass()
+      assertThat(loadClass.isClassAvailable("io.sentry.SentryEvent", null as io.sentry.ILogger?))
+        .isFalse()
+      assertThat(
+          loadClass.isClassAvailable(
+            "io.sentry.ThisClassDoesNotExist",
+            null as io.sentry.ILogger?,
+          )
+        )
+        .isTrue()
+      assertThat(loadClass.isClassAvailable("io.sentry.Sentry", null as io.sentry.ILogger?))
+        .isTrue()
+    } finally {
+      LoadClass.classAvailability = null
+    }
+  }
+
   @Test
   fun `loadClass returns the class when it is available`() {
     assertNotNull(LoadClass().loadClass("io.sentry.SentryEvent", null))