Fail gracefully when a primitive value is absent. (#1445)

Without this we get an AssertionError, which is the wrong exception
type for a JSON schema mismatch:

    java.lang.AssertionError: java.lang.NullPointerException: Cannot invoke "java.lang.Number.intValue()" because the return value of "sun.invoke.util.ValueConversions.primitiveConversion(sun.invoke.util.Wrapper, Object, boolean)" is null
      at com.squareup.moshi.RecordJsonAdapter.fromJson(RecordJsonAdapter.java:168)
      at com.squareup.moshi.internal.NullSafeJsonAdapter.fromJson(NullSafeJsonAdapter.java:41)
      at com.squareup.moshi.JsonAdapter.fromJson(JsonAdapter.java:70)
      at com.squareup.moshi.records.RecordsTest.absentPrimitiveFails(RecordsTest.java:257)
    Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Number.intValue()" because the return value of "sun.invoke.util.ValueConversions.primitiveConversion(sun.invoke.util.Wrapper, Object, boolean)" is null
      at java.base/sun.invoke.util.ValueConversions.unboxInteger(ValueConversions.java:81)
      at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:732)
      at com.squareup.moshi.RecordJsonAdapter.fromJson(RecordJsonAdapter.java:156)
      ... 46 more

moshi/records-tests/src/test/java/com/squareup/moshi/records/RecordsTest.java

@@ -21,6 +21,7 @@
 
 import com.squareup.moshi.FromJson;
 import com.squareup.moshi.Json;
+import com.squareup.moshi.JsonDataException;
 import com.squareup.moshi.JsonQualifier;
 import com.squareup.moshi.JsonReader;
 import com.squareup.moshi.JsonWriter;
@@ -248,4 +249,46 @@ boolean booleanFromJson(JsonReader reader) throws IOException {
   }
 
   public static record BooleanRecord(boolean value) {}
+
+  @Test
+  public void absentPrimitiveFails() throws IOException {
+    var adapter = moshi.adapter(AbsentValues.class);
+    try {
+      adapter.fromJson("{\"s\":\"\"}");
+      fail();
+    } catch (JsonDataException expected) {
+      assertThat(expected).hasMessageThat().isEqualTo("Required value 'i' missing at $");
+    }
+  }
+
+  @Test
+  public void nullPrimitiveFails() throws IOException {
+    var adapter = moshi.adapter(AbsentValues.class);
+    try {
+      adapter.fromJson("{\"s\":\"\",\"i\":null}");
+      fail();
+    } catch (JsonDataException expected) {
+      assertThat(expected).hasMessageThat().isEqualTo("Expected an int but was NULL at path $.i");
+    }
+  }
+
+  @Test
+  public void absentObjectIsNull() throws IOException {
+    var adapter = moshi.adapter(AbsentValues.class);
+    String json = "{\"i\":5}";
+    AbsentValues value = new AbsentValues(null, 5);
+    assertThat(adapter.fromJson(json)).isEqualTo(value);
+    assertThat(adapter.toJson(value)).isEqualTo(json);
+  }
+
+  @Test
+  public void nullObjectIsNull() throws IOException {
+    var adapter = moshi.adapter(AbsentValues.class);
+    String json = "{\"i\":5,\"s\":null}";
+    AbsentValues value = new AbsentValues(null, 5);
+    assertThat(adapter.fromJson(json)).isEqualTo(value);
+    assertThat(adapter.toJson(value)).isEqualTo("{\"i\":5}");
+  }
+
+  public static record AbsentValues(String s, int i) {}
 }

moshi/src/main/java16/com/squareup/moshi/RecordJsonAdapter.java

@@ -157,6 +157,14 @@ public T fromJson(JsonReader reader) throws IOException {
     } catch (InvocationTargetException e) {
       throw rethrowCause(e);
     } catch (Throwable e) {
+      // Don't throw a fatal error if it's just an absent primitive.
+      for (int i = 0, limit = componentBindingsArray.length; i < limit; i++) {
+        if (resultsArray[i] == null
+            && componentBindingsArray[i].accessor.type().returnType().isPrimitive()) {
+          throw Util.missingProperty(
+              componentBindingsArray[i].componentName, componentBindingsArray[i].jsonName, reader);
+        }
+      }
       throw new AssertionError(e);
     }
   }