feat: Add support for SENTRY_SAMPLE_RATE environment variable

Add `sampleRate` to `ExternalOptions` so it can be configured via the
`SENTRY_SAMPLE_RATE` environment variable or `sample-rate` property,
matching the behavior of other sample rate options.

Fixes GH-5091
Co-Authored-By: Claude <noreply@anthropic.com>

Author: adinauer

sentry/api/sentry.api

@@ -504,6 +504,7 @@ public final class io/sentry/ExternalOptions {
 	public fun getProguardUuid ()Ljava/lang/String;
 	public fun getProxy ()Lio/sentry/SentryOptions$Proxy;
 	public fun getRelease ()Ljava/lang/String;
+	public fun getSampleRate ()Ljava/lang/Double;
 	public fun getSendClientReports ()Ljava/lang/Boolean;
 	public fun getServerName ()Ljava/lang/String;
 	public fun getSpotlightConnectionUrl ()Ljava/lang/String;
@@ -552,6 +553,7 @@ public final class io/sentry/ExternalOptions {
 	public fun setProguardUuid (Ljava/lang/String;)V
 	public fun setProxy (Lio/sentry/SentryOptions$Proxy;)V
 	public fun setRelease (Ljava/lang/String;)V
+	public fun setSampleRate (Ljava/lang/Double;)V
 	public fun setSendClientReports (Ljava/lang/Boolean;)V
 	public fun setSendDefaultPii (Ljava/lang/Boolean;)V
 	public fun setSendModules (Ljava/lang/Boolean;)V

sentry/src/main/java/io/sentry/ExternalOptions.java

@@ -23,6 +23,7 @@ public final class ExternalOptions {
   private @Nullable Boolean enableUncaughtExceptionHandler;
   private @Nullable Boolean debug;
   private @Nullable Boolean enableDeduplication;
+  private @Nullable Double sampleRate;
   private @Nullable Double tracesSampleRate;
   private @Nullable Double profilesSampleRate;
   private @Nullable SentryOptions.RequestSize maxRequestBodySize;
@@ -77,6 +78,7 @@ public final class ExternalOptions {
         propertiesProvider.getBooleanProperty("uncaught.handler.enabled"));
     options.setPrintUncaughtStackTrace(
         propertiesProvider.getBooleanProperty("uncaught.handler.print-stacktrace"));
+    options.setSampleRate(propertiesProvider.getDoubleProperty("sample-rate"));
     options.setTracesSampleRate(propertiesProvider.getDoubleProperty("traces-sample-rate"));
     options.setProfilesSampleRate(propertiesProvider.getDoubleProperty("profiles-sample-rate"));
     options.setDebug(propertiesProvider.getBooleanProperty("debug"));
@@ -295,6 +297,14 @@ public void setEnableDeduplication(final @Nullable Boolean enableDeduplication)
     this.enableDeduplication = enableDeduplication;
   }
 
+  public @Nullable Double getSampleRate() {
+    return sampleRate;
+  }
+
+  public void setSampleRate(final @Nullable Double sampleRate) {
+    this.sampleRate = sampleRate;
+  }
+
   public @Nullable Double getTracesSampleRate() {
     return tracesSampleRate;
   }

sentry/src/main/java/io/sentry/SentryOptions.java

@@ -3394,6 +3394,9 @@ public void merge(final @NotNull ExternalOptions options) {
     if (options.getPrintUncaughtStackTrace() != null) {
       setPrintUncaughtStackTrace(options.getPrintUncaughtStackTrace());
     }
+    if (options.getSampleRate() != null) {
+      setSampleRate(options.getSampleRate());
+    }
     if (options.getTracesSampleRate() != null) {
       setTracesSampleRate(options.getTracesSampleRate());
     }

sentry/src/test/java/io/sentry/ExternalOptionsTest.kt

@@ -101,6 +101,11 @@ class ExternalOptionsTest {
     }
   }
 
+  @Test
+  fun `creates options with sampleRate using external properties`() {
+    withPropertiesFile("sample-rate=0.2") { assertEquals(0.2, it.sampleRate) }
+  }
+
   @Test
   fun `creates options with tracesSampleRate using external properties`() {
     withPropertiesFile("traces-sample-rate=0.2") { assertEquals(0.2, it.tracesSampleRate) }

sentry/src/test/java/io/sentry/SentryOptionsTest.kt

@@ -376,6 +376,7 @@ class SentryOptionsTest {
     externalOptions.setTag("tag1", "value1")
     externalOptions.setTag("tag2", "value2")
     externalOptions.enableUncaughtExceptionHandler = false
+    externalOptions.sampleRate = 0.3
     externalOptions.tracesSampleRate = 0.5
     externalOptions.profilesSampleRate = 0.5
     externalOptions.addInAppInclude("com.app")
@@ -433,6 +434,7 @@ class SentryOptionsTest {
     assertEquals(java.net.Proxy.Type.SOCKS, options.proxy!!.type)
     assertEquals(mapOf("tag1" to "value1", "tag2" to "value2"), options.tags)
     assertFalse(options.isEnableUncaughtExceptionHandler)
+    assertEquals(0.3, options.sampleRate)
     assertEquals(0.5, options.tracesSampleRate)
     assertEquals(0.5, options.profilesSampleRate)
     assertEquals(listOf("com.app"), options.inAppIncludes)