Auto-populate event_source_url from CAPI ParamBuilder

Summary:
# Problem

`com.facebook.capi.sdk:capi-param-builder` 1.3.0 (D106968654) exposes
`ParamBuilder.getEventSourceUrl()`, and the Java SDK's `Preference` now
has the `is_event_source_url_allowed` gate (D106971535). What is still
missing is the wiring in `Event` itself: callers who do
`event.setRequestContext(request)` get fbc / fbp handled by
`applyParamBuilderDefaults()` but `event_source_url` is never
auto-populated. This mirrors the Node.js wiring in D106966732, the PHP
wiring in D106907292, the Ruby wiring in D106704065, and the Python
wiring in D106698649.

# Solution

Extend `Event.applyParamBuilderDefaults()` so that after the existing
UserData fbc/fbp handling it also reads
`paramBuilder.getEventSourceUrl()` and assigns it to the event's
`eventSourceUrl` when:

- `preference.isEventSourceUrlAllowed()` is `true` (default), AND
- `eventSourceUrl` is currently null or empty (caller-supplied values
  always win, matching the precedence rule for fbc/fbp), AND
- the builder returned a non-empty URL.

Update the method docstring — it now fills empty `UserData` fields AND
empty `Event` fields.

Consistent with the existing fbc/fbp handling, this is wired and
unit-tested via a mocked `ParamBuilder`, but is a runtime no-op until
the deferred `paramBuilder.processRequestFromContext(context)` call in
`setRequestContext` is re-enabled (see the NOTE there). That deferral
was waiting on the Maven Central release of `capi-param-builder` to
publish the request-context methods, which the 1.3.0 bump (D106968654)
now satisfies; re-enabling the call (and the matching real-builder
guardrail assertions) is a separate follow-up, so this diff keeps the
event_source_url wiring in lock-step with how fbc/fbp are handled
today rather than changing that behavior here.

Differential Revision: D106972051

fbshipit-source-id: ee214cff0fcc2ee11a36e363b5d6431b7b4e40bb

Author: Jiaming You

src/main/java/com/facebook/ads/sdk/serverside/Event.java

@@ -638,9 +638,9 @@ public Event setRequestContext(Object context, Preference preference) {
   }
 
   /**
-   * Fills empty UserData fields from the ParamBuilder-extracted values, gated by Preference.
-   * No-op when {@link #setRequestContext} was never called. Idempotent: only fills fields that
-   * are currently empty, so the caller's explicit UserData values always take precedence
+   * Fills empty UserData and Event fields from the ParamBuilder-extracted values, gated by
+   * Preference. No-op when {@link #setRequestContext} was never called. Idempotent: only fills
+   * fields that are currently empty, so the caller's explicit values always take precedence
    * regardless of call order.
    *
    * <p>Invoked by {@link EventRequest} just before serializing the wire payload.
@@ -667,6 +667,13 @@ public Event setRequestContext(Object context, Preference preference) {
     }
 
     this.userData = ud;
+
+    String builderEventSourceUrl = this.paramBuilder.getEventSourceUrl();
+    if (Boolean.TRUE.equals(this.preference.isEventSourceUrlAllowed())
+        && (this.eventSourceUrl == null || this.eventSourceUrl.isEmpty())
+        && builderEventSourceUrl != null && !builderEventSourceUrl.isEmpty()) {
+      this.eventSourceUrl = builderEventSourceUrl;
+    }
   }
 
   /**

src/test/java/com/facebook/ads/sdk/serverside/EventRequestContextTest.java

@@ -84,6 +84,7 @@ public void testDefaultsToAllowAllPreferenceWhenNull() {
             assertTrue(pref.isFbpAllowed());
             assertTrue(pref.isClientIpAddressAllowed());
             assertTrue(pref.isReferrerUrlAllowed());
+            assertTrue(pref.isEventSourceUrlAllowed());
         }
     }
 
@@ -203,6 +204,7 @@ public void testPreferenceAllFalseSuppressesEveryAutoField() {
                  mockConstruction(ParamBuilder.class, (pb, ctx) -> {
                      when(pb.getFbc()).thenReturn("XX");
                      when(pb.getFbp()).thenReturn("YY");
+                     when(pb.getEventSourceUrl()).thenReturn("https://shop.example.com/cart");
                  })) {
             Preference pref = new Preference(false, false, false, false, false);
             Event event = new Event()
@@ -217,6 +219,63 @@ public void testPreferenceAllFalseSuppressesEveryAutoField() {
                 assertNull(ud.getFbc());
                 assertNull(ud.getFbp());
             }
+            assertNull(event.getEventSourceUrl());
+        }
+    }
+
+    // ----------------------------------------------------------------
+    // event_source_url auto-population (mocked ParamBuilder)
+    // ----------------------------------------------------------------
+
+    @Test
+    public void testAutoPopulatesEventSourceUrl() {
+        try (MockedConstruction<ParamBuilder> mocked =
+                 mockConstruction(ParamBuilder.class, (pb, ctx) -> {
+                     when(pb.getEventSourceUrl()).thenReturn("https://shop.example.com/cart");
+                 })) {
+            Event event = new Event()
+                .eventName("PageView")
+                .eventTime(1700000060L)
+                .setRequestContext(new Object());
+
+            event.applyParamBuilderDefaults();
+            assertEquals("https://shop.example.com/cart", event.getEventSourceUrl());
+        }
+    }
+
+    @Test
+    public void testCallerSuppliedEventSourceUrlTakesPrecedence() {
+        try (MockedConstruction<ParamBuilder> mocked =
+                 mockConstruction(ParamBuilder.class, (pb, ctx) -> {
+                     when(pb.getEventSourceUrl()).thenReturn("https://from-builder/");
+                 })) {
+            Event event = new Event()
+                .eventName("Lead")
+                .eventTime(1700000061L)
+                .eventSourceUrl("https://from-caller/")
+                .setRequestContext(new Object());
+
+            event.applyParamBuilderDefaults();
+            assertEquals("https://from-caller/", event.getEventSourceUrl());
+        }
+    }
+
+    @Test
+    public void testPreferenceGatesEventSourceUrl() {
+        try (MockedConstruction<ParamBuilder> mocked =
+                 mockConstruction(ParamBuilder.class, (pb, ctx) -> {
+                     when(pb.getFbc()).thenReturn("WITHFBC");
+                     when(pb.getEventSourceUrl()).thenReturn("https://from-builder/");
+                 })) {
+            Preference pref = new Preference(true, true, true, true, false);
+            Event event = new Event()
+                .eventName("PageView")
+                .eventTime(1700000062L)
+                .setRequestContext(new Object(), pref);
+
+            event.applyParamBuilderDefaults();
+            assertEquals("WITHFBC", event.getUserData().getFbc());
+            assertNull(event.getEventSourceUrl());
         }
     }