Fixes a bug where calling addChildFields more than once with the same arguments lead to a 'Cannot follow the same aggregate relationship twice' error

Author: jamessimone

force-app/repository/Repository.cls

@@ -1,6 +1,7 @@
 @SuppressWarnings('PMD.AvoidBooleanMethodParameters,PMD.ExcessiveParameterList,PMD.ExcessivePublicCount')
 public virtual without sharing class Repository implements IRepository {
   private final Map<Schema.SObjectField, String> childToRelationshipNames;
+  private final Map<String, String> relationshipNameToChildQuery = new Map<String, String>();
   private final IDML dml;
   @TestVisible
   private final List<Schema.SObjectField> queryFields;
@@ -174,6 +175,7 @@ public virtual without sharing class Repository implements IRepository {
   ) {
     Repository cr = (Repository) childRepo;
     cr.selectFields.addAll(cr.addSelectFields());
+    cr.selectFields.addAll(cr.relationshipNameToChildQuery.values());
     Set<String> localSelectFields = cr.selectFields;
     localSelectFields.remove('Id');
 
@@ -213,12 +215,12 @@ public virtual without sharing class Repository implements IRepository {
       this.childBindVarKeys.addAll(query.getBindVars().keySet());
     }
 
-    this.selectFields.add(
-      String.format(
-        baseSubselect,
-        new List<String>{ String.join(childFieldNames, ','), this.childToRelationshipNames.get(childFieldToken) }
-      )
+    String relationshipName = this.childToRelationshipNames.get(childFieldToken);
+    String childFieldsToAdd = String.format(
+      baseSubselect,
+      new List<String>{ String.join(childFieldNames, ','), this.childToRelationshipNames.get(childFieldToken) }
     );
+    this.relationshipNameToChildQuery.put(relationshipName, childFieldsToAdd);
     return this;
   }
 
@@ -301,6 +303,7 @@ public virtual without sharing class Repository implements IRepository {
       localSelectFields.addAll(this.selectFields);
       this.baseSelectUsed = false;
     }
+    localSelectFields.addAll(this.relationshipNameToChildQuery.values());
     return 'SELECT ' + String.join(localSelectFields, ', ') + '\nFROM ' + this.repoType;
   }
 

force-app/repository/RepositoryTest.cls

@@ -144,6 +144,52 @@ private class RepositoryTest {
     Assert.areEqual(acc.Name, returnedCon.Account.Name);
   }
 
+  @IsTest
+  static void itSupportsCallingAddChildFieldsWithSameArgumentsTwice() {
+    IRepository repo = new AccountRepo()
+      .addChildFields(
+        Contact.AccountId,
+        new List<QueryField>{
+          new QueryField(Contact.AccountId),
+          new QueryField(Contact.LastName),
+          new QueryField(
+            new List<Schema.SObjectField>{ Contact.AccountId },
+            new List<Schema.SObjectField>{ Account.Name }
+          )
+        },
+        new List<Query>{ Query.notEquals(Account.Name, 'somepredicate') },
+        new Map<String, RepositorySortOrder>(),
+        1
+      );
+    repo.addChildFields(
+      Contact.AccountId,
+      new List<QueryField>{
+        new QueryField(Contact.AccountId),
+        new QueryField(Contact.LastName),
+        new QueryField(
+          new List<Schema.SObjectField>{ Contact.AccountId },
+          new List<Schema.SObjectField>{ Account.Name }
+        )
+      },
+      new List<Query>{ Query.notEquals(Account.Name, 'somepredicate') },
+      new Map<String, RepositorySortOrder>(),
+      1
+    );
+
+    Account acc = new Account(Name = 'Parent');
+    insert acc;
+    Contact con = new Contact(AccountId = acc.Id, LastName = 'Child');
+    insert con;
+
+    List<Account> accounts = repo.getAll();
+
+    Assert.areEqual(1, accounts.size());
+    Assert.areEqual(1, accounts.get(0).Contacts.size());
+    Contact returnedCon = accounts.get(0).Contacts.get(0);
+    Assert.areEqual(con.LastName, returnedCon.LastName);
+    Assert.areEqual(acc.Name, returnedCon.Account.Name);
+  }
+
   @IsTest
   static void itShouldAddChildFieldsFromRepo() {
     IRepository repo = new AccountRepo()