improve code

Author: cherylEnkidu

Firestore/Swift/Source/Helper/PipelineHelper.swift

@@ -38,6 +38,7 @@ enum Helper {
       }
       let alias = value.alias
       if result.keys.contains(alias) {
+        // TODO: Add tests to verify the behaviour.
         fatalError("Duplicate alias '\(alias)' found in selectables.")
       }
       result[alias] = value.expr
@@ -52,6 +53,7 @@ enum Helper {
 
         let alias = aliasedAggregate.alias
         if result.keys.contains(alias) {
+          // TODO: Add tests to verify the behaviour.
           fatalError("Duplicate alias '\(alias)' found in accumulators.")
         }
         result[alias] = aliasedAggregate.aggregate
@@ -84,11 +86,11 @@ enum Helper {
     if let exprValue = value as? Expression {
       return exprValue.toBridge()
     } else if let aggregateFunctionValue = value as? AggregateFunction {
-      return aggregateFunctionValue.toBridge()
+      return aggregateFunctionValue.bridge
     } else if let dictionaryValue = value as? [String: Sendable?] {
       let mappedValue: [String: Sendable] = dictionaryValue.mapValues {
         if let aggFunc = $0 as? AggregateFunction {
-          return aggFunc.toBridge()
+          return aggFunc.bridge
         }
         return sendableToExpr($0).toBridge()
       }

Firestore/Swift/Source/Stages.swift

@@ -151,8 +151,8 @@ class AddFields: Stage {
   init(selectables: [Selectable]) {
     self.selectables = selectables
     let map = Helper.selectablesToMap(selectables: selectables)
-    let objc_accumulators = map.mapValues { $0.toBridge() }
-    bridge = AddFieldsStageBridge(fields: objc_accumulators)
+    let objcAccumulators = map.mapValues { $0.toBridge() }
+    bridge = AddFieldsStageBridge(fields: objcAccumulators)
   }
 }
 

Firestore/Swift/Source/SwiftAPI/Pipeline/Aggregates/AggregateFunction.swift

@@ -12,12 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-extension AggregateFunction {
-  func toBridge() -> AggregateFunctionBridge {
-    return (self as AggregateBridgeWrapper).bridge
-  }
-}
-
 /// Represents an aggregate function in a pipeline.
 ///
 /// An `AggregateFunction` is a function that computes a single value from a set of input values.

Firestore/Swift/Tests/Integration/PipelineTests.swift

@@ -3243,16 +3243,6 @@ class PipelineIntegrationTests: FSTIntegrationTestCase {
     }
   }
 
-  func testAddFieldsThrowsOnDuplicateAliases() async throws {
-    let collRef = collectionRef(withDocuments: bookDocs)
-    let db = collRef.firestore
-    _ = db.pipeline()
-      .collection(collRef.path)
-      .select([Field("title"), Field("author")])
-      .addFields([Constant("bar").as("foo"), Constant("baz").as("foo")])
-      .sort([Field("author").ascending()])
-  }
-
   func testSupportsTimestampConversions() async throws {
     let db = firestore()
     let randomCol = collectionRef() // Unique collection for this test