1 files changed, 49 insertions, 0 deletions

diff --git a/src/WixToolset.Core/Link/ReportConflictingSymbolsCommand.cs b/src/WixToolset.Core/Link/ReportConflictingSymbolsCommand.cs
new file mode 100644
index 00000000..39c3a5c2
--- /dev/null
+++ b/src/WixToolset.Core/Link/ReportConflictingSymbolsCommand.cs
@@ -0,0 +1,49 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Link
+{
+    using System.Collections.Generic;
+    using System.Linq;
+    using WixToolset.Data;
+
+    public class ReportConflictingSymbolsCommand : ICommand
+    {
+        private IEnumerable<Symbol> possibleConflicts;
+        private IEnumerable<Section> resolvedSections;
+
+        public ReportConflictingSymbolsCommand(IEnumerable<Symbol> possibleConflicts, IEnumerable<Section> resolvedSections)
+        {
+            this.possibleConflicts = possibleConflicts;
+            this.resolvedSections = resolvedSections;
+        }
+
+        public void Execute()
+        {
+            // Do a quick check if there are any possibly conflicting symbols that don't come from tables that allow
+            // overriding. Hopefully the symbols with possible conflicts list is usually very short list (empty should
+            // be the most common). If we find any matches, we'll do a more costly check to see if the possible conflicting
+            // symbols are in sections we actually referenced. From the resulting set, show an error for each duplicate
+            // (aka: conflicting) symbol. This should catch any rows with colliding primary keys (since symbols are based
+            // on the primary keys of rows).
+            List<Symbol> illegalDuplicates = possibleConflicts.Where(s => "WixAction" != s.Row.Table.Name && "WixVariable" != s.Row.Table.Name).ToList();
+            if (0 < illegalDuplicates.Count)
+            {
+                HashSet<Section> referencedSections = new HashSet<Section>(resolvedSections);
+                foreach (Symbol referencedDuplicateSymbol in illegalDuplicates.Where(s => referencedSections.Contains(s.Section)))
+                {
+                    List<Symbol> actuallyReferencedDuplicateSymbols = referencedDuplicateSymbol.PossiblyConflictingSymbols.Where(s => referencedSections.Contains(s.Section)).ToList();
+
+                    if (actuallyReferencedDuplicateSymbols.Any())
+                    {
+                        Messaging.Instance.OnMessage(WixErrors.DuplicateSymbol(referencedDuplicateSymbol.Row.SourceLineNumbers, referencedDuplicateSymbol.Name));
+
+                        foreach (Symbol duplicate in actuallyReferencedDuplicateSymbols)
+                        {
+                            Messaging.Instance.OnMessage(WixErrors.DuplicateSymbol2(duplicate.Row.SourceLineNumbers));
+                        }
+                    }
+                }
+            }
+        }
+    }
+}