Fix duplicate key handling (#10049)

NikolaMilosavljevic · web-flow · commit 791a389797e0 · 2026-03-25T11:28:58.000-07:00
Fixes #10025 ## Problem After migrating from Newtonsoft.Json to System.Text.Json, loading template.json files with duplicate case-insensitive property keys (e.g. `"Empty"` and `"empty"`) throws an `ArgumentException`: ``` System.ArgumentException: An item with the same key has already been added. Key: empty (Parameter 'key') at System.Collections.Generic.OrderedDictionary`2.Add(TKey key, TValue value) at System.Text.Json.Nodes.JsonObject.InitializeDictionary() at System.Text.Json.Nodes.JsonObject.get_Count() ... at Microsoft.TemplateEngine.Orchestrator.RunnableProjects.ConfigModel.TemplateConfigModel..ctor(...) ``` This affected MAUI templates (`maui-blazor`, `maui-blazor-solution`) which intentionally had both `"Empty"` (PascalCase backward-compat alias) and `"empty"` (lowercase) symbol definitions. ## Root Cause In `src/Shared/JExtensions.cs`, the `NodeOptions` field was configured with `PropertyNameCaseInsensitive = true`: ```csharp private static readonly JsonNodeOptions NodeOptions = new() { PropertyNameCaseInsensitive = true }; ``` This caused `JsonObject` to use a case-insensitive internal dictionary. When any operation triggered `JsonObject.InitializeDictionary()` (e.g. accessing `.Count`, iterating via `.ToList()`), it attempted to insert both `"Empty"` and `"empty"` into the same case-insensitive dictionary, throwing on the duplicate. This setting was **redundant** — all case-insensitive property lookups in the codebase already go through the `GetPropertyCaseInsensitive()` helper method, which manually performs a case-insensitive fallback search. ## Fix **File changed:** `src/Shared/JExtensions.cs` - Removed the `NodeOptions` field entirely (it only existed to set `PropertyNameCaseInsensitive = true`) - Replaced all 6 usages of `NodeOptions` in `JsonNode.Parse()` calls with `null` (uses default `JsonNodeOptions`, which is case-sensitive) This means `JsonObject` now stores properties with their original casing and uses a case-sensitive internal dictionary — which tolerates keys like `"Empty"` and `"empty"` coexisting. Case-insensitive lookups continue to work through the existing `GetPropertyCaseInsensitive()` helper. ## Test Added **File:** `test/Microsoft.TemplateEngine.Orchestrator.RunnableProjects.UnitTests/TemplateConfigTests/GenericTests.cs` Added `CanReadTemplateWithDuplicateCaseInsensitiveSymbolKeys` — a regression test that verifies a template.json with symbols `"Empty"` and `"empty"` loads without throwing.
diff --git a/src/Shared/JExtensions.cs b/src/Shared/JExtensions.cs
@@ -17,7 +17,6 @@ namespace Microsoft.TemplateEngine
     internal static class JExtensions
     {
         private static readonly JsonDocumentOptions DocOptions = new() { CommentHandling = JsonCommentHandling.Skip, AllowTrailingCommas = true };
-        private static readonly JsonNodeOptions NodeOptions = new() { PropertyNameCaseInsensitive = true };
         private static readonly JsonSerializerOptions SerializerOptions = new()
         {
             PropertyNameCaseInsensitive = true,
@@ -387,7 +386,7 @@ internal static JsonObject ReadJObjectFromIFile(this IFile file)
             using Stream s = file.OpenRead();
             using TextReader tr = new StreamReader(s, System.Text.Encoding.UTF8, true);
             string json = tr.ReadToEnd();
-            return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)
+            return (JsonObject?)JsonNode.Parse(json, null, DocOptions)
                 ?? throw new InvalidOperationException("Failed to parse JSON from file.");
         }
 
@@ -396,7 +395,7 @@ internal static JsonObject ReadObject(this IPhysicalFileSystem fileSystem, strin
             using Stream fileStream = fileSystem.OpenRead(path);
             using var textReader = new StreamReader(fileStream, System.Text.Encoding.UTF8, true);
             string json = textReader.ReadToEnd();
-            return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)
+            return (JsonObject?)JsonNode.Parse(json, null, DocOptions)
                 ?? throw new InvalidOperationException($"Failed to parse JSON from '{path}'.");
         }
 
@@ -480,7 +479,7 @@ internal static bool TryGetValueCaseInsensitive(this JsonObject obj, string key,
         /// </summary>
         internal static JsonObject ParseJsonObject(string json)
         {
-            return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)
+            return (JsonObject?)JsonNode.Parse(json, null, DocOptions)
                 ?? throw new InvalidOperationException("Failed to parse JSON string as JsonObject.");
         }
 
@@ -489,7 +488,7 @@ internal static JsonObject ParseJsonObject(string json)
         /// </summary>
         internal static JsonNode? ParseJsonNode(string json)
         {
-            return JsonNode.Parse(json, NodeOptions, DocOptions);
+            return JsonNode.Parse(json, null, DocOptions);
         }
 
         /// <summary>
@@ -503,7 +502,7 @@ internal static JsonObject ParseJsonObject(string json)
         internal static JsonObject FromObject(object obj)
         {
             string json = JsonSerializer.Serialize(obj, SerializerOptions);
-            return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)
+            return (JsonObject?)JsonNode.Parse(json, null, DocOptions)
                 ?? throw new InvalidOperationException("Failed to round-trip object to JsonObject.");
         }
 
@@ -512,7 +511,7 @@ internal static JsonObject FromObject(object obj)
         /// </summary>
         internal static JsonObject DeepCloneObject(this JsonObject source)
         {
-            return (JsonObject?)JsonNode.Parse(source.ToJsonString(), NodeOptions, DocOptions)
+            return (JsonObject?)JsonNode.Parse(source.ToJsonString(), null, DocOptions)
                 ?? throw new InvalidOperationException("Failed to deep clone JsonObject.");
         }
 
diff --git a/test/Microsoft.TemplateEngine.Orchestrator.RunnableProjects.UnitTests/TemplateConfigTests/GenericTests.cs b/test/Microsoft.TemplateEngine.Orchestrator.RunnableProjects.UnitTests/TemplateConfigTests/GenericTests.cs
@@ -54,5 +54,44 @@ public void CanReadTemplateFromStream()
             Assert.Equal(2, templateConfigModel.PrimaryOutputs.Count);
             Assert.Equal(new[] { "bar.cs", "bar/bar.cs" }, templateConfigModel.PrimaryOutputs.Select(po => po.Path).OrderBy(po => po));
         }
+
+        [Fact]
+        public void CanReadTemplateWithDuplicateCaseInsensitiveSymbolKeys()
+        {
+            // Regression test: template.json with symbols that differ only by case
+            // (e.g. "Empty" and "empty") should load without throwing.
+            // See https://github.com/dotnet/templating/issues/10047
+            string templateWithDuplicateKeys = /*lang=json*/ """
+                {
+                  "author": "Test Asset",
+                  "classifications": [ "Test Asset" ],
+                  "name": "TemplateWithDuplicateKeys",
+                  "identity": "TestAssets.TemplateWithDuplicateKeys",
+                  "shortName": "dupkeys",
+                  "symbols": {
+                    "Empty": {
+                      "type": "parameter",
+                      "datatype": "bool",
+                      "defaultValue": "false",
+                      "description": "PascalCase variant"
+                    },
+                    "empty": {
+                      "type": "parameter",
+                      "datatype": "bool",
+                      "defaultValue": "false",
+                      "description": "lowercase variant"
+                    }
+                  }
+                }
+                """;
+
+            var exception = Record.Exception(() => TemplateConfigModel.FromString(templateWithDuplicateKeys));
+            Assert.Null(exception);
+
+            TemplateConfigModel configModel = TemplateConfigModel.FromString(templateWithDuplicateKeys);
+            Assert.Equal("TemplateWithDuplicateKeys", configModel.Name);
+            // Both symbols should be accessible (last-in-wins for case-sensitive dict, both kept)
+            Assert.NotEmpty(configModel.Symbols);
+        }
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -17,7 +17,6 @@ namespace Microsoft.TemplateEngine`
`17`	`17`	`internal static class JExtensions`
`18`	`18`	`{`
`19`	`19`	`private static readonly JsonDocumentOptions DocOptions = new() { CommentHandling = JsonCommentHandling.Skip, AllowTrailingCommas = true };`
`20`		`- private static readonly JsonNodeOptions NodeOptions = new() { PropertyNameCaseInsensitive = true };`
`21`	`20`	`private static readonly JsonSerializerOptions SerializerOptions = new()`
`22`	`21`	`{`
`23`	`22`	`PropertyNameCaseInsensitive = true,`
`@@ -387,7 +386,7 @@ internal static JsonObject ReadJObjectFromIFile(this IFile file)`
`387`	`386`	`using Stream s = file.OpenRead();`
`388`	`387`	`using TextReader tr = new StreamReader(s, System.Text.Encoding.UTF8, true);`
`389`	`388`	`string json = tr.ReadToEnd();`
`390`		`- return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)`
	`389`	`+ return (JsonObject?)JsonNode.Parse(json, null, DocOptions)`
`391`	`390`	`?? throw new InvalidOperationException("Failed to parse JSON from file.");`
`392`	`391`	`}`
`393`	`392`
`@@ -396,7 +395,7 @@ internal static JsonObject ReadObject(this IPhysicalFileSystem fileSystem, strin`
`396`	`395`	`using Stream fileStream = fileSystem.OpenRead(path);`
`397`	`396`	`using var textReader = new StreamReader(fileStream, System.Text.Encoding.UTF8, true);`
`398`	`397`	`string json = textReader.ReadToEnd();`
`399`		`- return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)`
	`398`	`+ return (JsonObject?)JsonNode.Parse(json, null, DocOptions)`
`400`	`399`	`?? throw new InvalidOperationException($"Failed to parse JSON from '{path}'.");`
`401`	`400`	`}`
`402`	`401`
`@@ -480,7 +479,7 @@ internal static bool TryGetValueCaseInsensitive(this JsonObject obj, string key,`
`480`	`479`	`/// </summary>`
`481`	`480`	`internal static JsonObject ParseJsonObject(string json)`
`482`	`481`	`{`
`483`		`- return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)`
	`482`	`+ return (JsonObject?)JsonNode.Parse(json, null, DocOptions)`
`484`	`483`	`?? throw new InvalidOperationException("Failed to parse JSON string as JsonObject.");`
`485`	`484`	`}`
`486`	`485`
`@@ -489,7 +488,7 @@ internal static JsonObject ParseJsonObject(string json)`
`489`	`488`	`/// </summary>`
`490`	`489`	`internal static JsonNode? ParseJsonNode(string json)`
`491`	`490`	`{`
`492`		`- return JsonNode.Parse(json, NodeOptions, DocOptions);`
	`491`	`+ return JsonNode.Parse(json, null, DocOptions);`
`493`	`492`	`}`
`494`	`493`
`495`	`494`	`/// <summary>`
`@@ -503,7 +502,7 @@ internal static JsonObject ParseJsonObject(string json)`
`503`	`502`	`internal static JsonObject FromObject(object obj)`
`504`	`503`	`{`
`505`	`504`	`string json = JsonSerializer.Serialize(obj, SerializerOptions);`
`506`		`- return (JsonObject?)JsonNode.Parse(json, NodeOptions, DocOptions)`
	`505`	`+ return (JsonObject?)JsonNode.Parse(json, null, DocOptions)`
`507`	`506`	`?? throw new InvalidOperationException("Failed to round-trip object to JsonObject.");`
`508`	`507`	`}`
`509`	`508`
`@@ -512,7 +511,7 @@ internal static JsonObject FromObject(object obj)`
`512`	`511`	`/// </summary>`
`513`	`512`	`internal static JsonObject DeepCloneObject(this JsonObject source)`
`514`	`513`	`{`
`515`		`- return (JsonObject?)JsonNode.Parse(source.ToJsonString(), NodeOptions, DocOptions)`
	`514`	`+ return (JsonObject?)JsonNode.Parse(source.ToJsonString(), null, DocOptions)`
`516`	`515`	`?? throw new InvalidOperationException("Failed to deep clone JsonObject.");`
`517`	`516`	`}`
`518`	`517`