Simplify YAML/JSON parser code path with Result pattern (#18713)

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Author: anthony-c-martin

src/Bicep.Core.IntegrationTests/ModuleTests.cs

@@ -182,8 +182,6 @@ param inputb string
             });
         }
 
-        private delegate bool TryReadDelegate(Uri fileUri, out string? fileContents, out DiagnosticBuilder.DiagnosticBuilderDelegate? failureBuilder);
-
         [TestMethod]
         public void SourceFileGroupingBuilder_build_should_throw_diagnostic_exception_if_entrypoint_file_read_fails()
         {

src/Bicep.Core.UnitTests/Semantics/ObjectDeserializationTests.cs

@@ -95,7 +95,7 @@ public void JSON_file_content_gets_deserialized_into_JSON()
         private static void CompareSimpleJSON(string json)
         {
             var arguments = new FunctionArgumentSyntax[4];
-            new YamlObjectParser().TryExtractFromObject(json, null, [arguments[0]], out var errorDiagnostic, out JToken? jToken);
+            new YamlObjectParser().TryExtractFromObject(json, null, [arguments[0]]).IsSuccess(out var jToken);
             var correctList = new List<int> { 1, 2 };
             var correctObject = new Dictionary<string, int> { { "nestedInt", 1 }, };
 
@@ -133,7 +133,7 @@ public void Unparsable_YAML()
                     - 2";
 
             var span = new TextSpan(0, 10 - 0);
-            new YamlObjectParser().TryExtractFromObject(invalidYml, null, [span], out var errorDiagnostic, out JToken? jToken);
+            new YamlObjectParser().TryExtractFromObject(invalidYml, null, [span]).IsSuccess(out _, out var errorDiagnostic);
             Assert.AreEqual(errorDiagnostic!.Code, "BCP340");
         }
 
@@ -156,7 +156,7 @@ public void Unparsable_JSON()
                     - 2";
 
             var span = new TextSpan(0, 10 - 0);
-            new JsonObjectParser().TryExtractFromObject(invalidJson, null, [span], out var errorDiagnostic, out JToken? jToken);
+            new JsonObjectParser().TryExtractFromObject(invalidJson, null, [span]).IsSuccess(out _, out var errorDiagnostic);
             Assert.AreEqual(errorDiagnostic!.Code, "BCP186");
         }
 
@@ -165,7 +165,7 @@ public void Complex_JSON_gets_deserialized_into_JSON()
         {
             var json = COMPLEX_JSON;
             var arguments = new FunctionArgumentSyntax[4];
-            new YamlObjectParser().TryExtractFromObject(json, null, [arguments[0]], out var errorDiagnostic, out JToken? jToken);
+            new YamlObjectParser().TryExtractFromObject(json, null, [arguments[0]]).IsSuccess(out var jToken);
             var expectedValue = "```bicep\ndateTimeFromEpoch([epochTime: int]): string\n\n```\nConverts an epoch time integer value to an [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) dateTime string.\n";
             Assert.AreEqual(expectedValue, jToken!["documentation"]!["value"]);
         }
@@ -188,7 +188,7 @@ public void Simple_YAML_file_content_gets_deserialized_into_JSON()
                      zip: 99970";
 
             var arguments = new FunctionArgumentSyntax[4];
-            new YamlObjectParser().TryExtractFromObject(yml, null, [arguments[0]], out var errorDiagnostic, out JToken? jToken);
+            new YamlObjectParser().TryExtractFromObject(yml, null, [arguments[0]]).IsSuccess(out var jToken);
 
             Assert.AreEqual("George Washington", jToken!["name"]);
             Assert.AreEqual("400", jToken["addresses"]!["home"]!["street"]!["house_number"]);

src/Bicep.Core/Semantics/IObjectParser.cs

@@ -5,10 +5,9 @@
 using Bicep.Core.Text;
 using Newtonsoft.Json.Linq;
 
-namespace Bicep.Core.Semantics
+namespace Bicep.Core.Semantics;
+
+public interface IObjectParser
 {
-    public interface IObjectParser
-    {
-        bool TryExtractFromObject(string fileContent, string? tokenSelectorPath, IPositionable[] positionable, [NotNullWhen(false)] out IDiagnostic? errorDiagnostic, [NotNullWhen(true)] out JToken? newToken);
-    }
+    ResultWithDiagnostic<JToken> TryExtractFromObject(string fileContent, string? tokenSelectorPath, IPositionable[] positionable);
 }

src/Bicep.Core/Semantics/JsonObjectParser.cs

@@ -5,16 +5,17 @@
 using Microsoft.WindowsAzure.ResourceStack.Common.Json;
 using Newtonsoft.Json.Linq;
 
-namespace Bicep.Core.Semantics
+namespace Bicep.Core.Semantics;
+
+public class JsonObjectParser : ObjectParser
 {
-    public class JsonObjectParser : ObjectParser
+    protected override ResultWithDiagnostic<JToken> ExtractTokenFromObject(string fileContent, IPositionable positionable)
     {
-        /// <summary>
-        /// TryFromJson returns null if the fileContent is not a valid JSON object
-        /// </summary>
-        override protected JToken ExtractTokenFromObject(string fileContent)
-            => fileContent.TryFromJson<JToken>();
-        override protected Diagnostic GetExtractTokenErrorType(IPositionable positionable)
-            => DiagnosticBuilder.ForPosition(positionable).UnparsableJsonType();
+        if (fileContent.TryFromJson<JToken>() is {} jToken)
+        {
+            return new(jToken);
+        }
+
+        return new(DiagnosticBuilder.ForPosition(positionable).UnparsableJsonType());
     }
 }

src/Bicep.Core/Semantics/Namespaces/SystemNamespaceType.cs

@@ -1431,7 +1431,7 @@ private static FunctionResult LoadContentResultBuilder(ObjectParser objectParser
 
             if (TryLoadTextContentFromFile(model, diagnostics, (arguments[0], argumentTypes[0]), arguments.Length > 2 ? (arguments[2], argumentTypes[2]) : null, characterLimit)
                 .IsSuccess(out var result, out var errorDiagnostic) &&
-                objectParser.TryExtractFromObject(result.Content, tokenSelectorPath, positionables, out errorDiagnostic, out var token))
+                objectParser.TryExtractFromObject(result.Content, tokenSelectorPath, positionables).IsSuccess(out var token, out errorDiagnostic))
             {
                 return new(ConvertJsonToBicepType(token), ConvertJsonToExpression(token));
             }

src/Bicep.Core/Semantics/ObjectParser.cs

@@ -3,76 +3,43 @@
 using System.Diagnostics.CodeAnalysis;
 using Bicep.Core.Diagnostics;
 using Bicep.Core.Text;
+using Bicep.Core.Utils;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 
-namespace Bicep.Core.Semantics
+namespace Bicep.Core.Semantics;
+
+public abstract class ObjectParser : IObjectParser
 {
-    public abstract class ObjectParser : IObjectParser
+    public ResultWithDiagnostic<JToken> TryExtractFromObject(string fileContent, string? tokenSelectorPath, IPositionable[] positionable)
     {
-        public bool TryExtractFromObject(string fileContent, string? tokenSelectorPath, IPositionable[] positionable, [NotNullWhen(false)] out IDiagnostic? errorDiagnostic, [NotNullWhen(true)] out JToken? newToken)
+        var result = ExtractTokenFromObject(fileContent, positionable[0]);
+        if (result.IsSuccess(out var newToken) && tokenSelectorPath is {})
         {
-            errorDiagnostic = null;
-            newToken = this.ExtractTokenFromObject(fileContent);
-            if (newToken is not { })
-            {
-                // Instead of catching and returning the parsing exception, we simply return a generic error.
-                // This avoids having to deal with localization, and avoids possible confusion regarding line endings in the message.
-                errorDiagnostic = this.GetExtractTokenErrorType(positionable[0]);
-                return false;
-            }
-            if (tokenSelectorPath is not null)
-            {
-                return this.TryExtractFromTokenByPath(newToken, tokenSelectorPath, positionable[1], out errorDiagnostic, out newToken);
-            }
-            return true;
+            return TryExtractFromTokenByPath(newToken, tokenSelectorPath, positionable[1]);
         }
-        protected abstract JToken? ExtractTokenFromObject(string fileContent);
 
-        protected abstract Diagnostic GetExtractTokenErrorType(IPositionable positionable);
+        return result;
+    }
 
-        private bool TryExtractFromTokenByPath(JToken token, string tokenSelectorPath, IPositionable positionable, [NotNullWhen(false)] out IDiagnostic? errorDiagnostic, out JToken newToken)
-        {
-            newToken = token;
-            errorDiagnostic = null;
-            if (tokenSelectorPath is null)
-            {
-                return true;
-            }
+    protected abstract ResultWithDiagnostic<JToken> ExtractTokenFromObject(string fileContent, IPositionable positionable);
 
-            try
-            {
-                var selectTokens = token.SelectTokens(tokenSelectorPath, false).ToList();
+    private static ResultWithDiagnostic<JToken> TryExtractFromTokenByPath(JToken token, string tokenSelectorPath, IPositionable positionable)
+    {
+        try
+        {
+            var selectTokens = token.SelectTokens(tokenSelectorPath, false).ToList();
 
-                switch (selectTokens.Count)
-                {
-                    case 0:
-                        {
-                            errorDiagnostic = DiagnosticBuilder.ForPosition(positionable).NoJsonTokenOnPathOrPathInvalid();
-                            return false;
-                        }
-                    case 1:
-                        {
-                            newToken = selectTokens.First();
-                            break;
-                        }
-                    default:
-                        {
-                            newToken = new JArray(selectTokens);
-                            break;
-                        }
-                }
-                return true;
-            }
-            catch (JsonException)
+            return selectTokens switch
             {
-                //path is invalid or user hasn't finished typing it yet
-                errorDiagnostic = DiagnosticBuilder.ForPosition(positionable).NoJsonTokenOnPathOrPathInvalid();
-                return false;
-            }
-
-
+                [] => new(DiagnosticBuilder.ForPosition(positionable).NoJsonTokenOnPathOrPathInvalid()),
+                [var singleToken] => new(singleToken),
+                _ => new(new JArray(selectTokens))
+            };
+        }
+        catch (JsonException)
+        {
+            return new(DiagnosticBuilder.ForPosition(positionable).NoJsonTokenOnPathOrPathInvalid());
         }
-
     }
 }

src/Bicep.Core/Semantics/YamlObjectParser.cs

@@ -6,27 +6,29 @@
 using Newtonsoft.Json.Linq;
 using SharpYaml.Serialization;
 
-namespace Bicep.Core.Semantics
+namespace Bicep.Core.Semantics;
+
+public class YamlObjectParser : ObjectParser
 {
-    public class YamlObjectParser : ObjectParser
+    protected override ResultWithDiagnostic<JToken> ExtractTokenFromObject(string fileContent, IPositionable positionable)
     {
-        /// <summary>
-        /// Deserialize raises an exception if the fileContent is not a valid YAML object
-        /// </summary>
-        override protected JToken? ExtractTokenFromObject(string fileContent)
+        if (TryDeserialize(fileContent) is { } deserialized)
         {
-            try
-            {
-                return new Serializer().Deserialize(fileContent) is { } deserialized ? JToken.FromObject(deserialized) : null;
-            }
-            catch
-            {
-                return null;
-            }
+            return new(JToken.FromObject(deserialized));
         }
 
-        override protected Diagnostic GetExtractTokenErrorType(IPositionable positionable)
-            => DiagnosticBuilder.ForPosition(positionable).UnparsableYamlType();
+        return new(DiagnosticBuilder.ForPosition(positionable).UnparsableYamlType());
+    }
 
+    private static object? TryDeserialize(string fileContent)
+    {
+        try
+        {
+            return new Serializer().Deserialize(fileContent);
+        }
+        catch
+        {
+            return null;
+        }
     }
 }

src/Bicep.Core/TypeSystem/ArmFunctionReturnTypeEvaluator.cs

@@ -43,7 +43,7 @@ public static class ArmFunctionReturnTypeEvaluator
             args[i + prefixArgsArray.Length] = new(converted);
         }
 
-        if (EvaluateOperatorAsArmFunction(armFunctionName, out var result, out var builderFunc, args))
+        if (EvaluateOperatorAsArmFunction(armFunctionName, args).IsSuccess(out var result, out var builderFunc))
         {
             if (TypeHelper.TryCreateTypeLiteral(result) is { } literalType)
             {
@@ -113,28 +113,22 @@ public static class ArmFunctionReturnTypeEvaluator
         return target;
     }
 
-    private static bool EvaluateOperatorAsArmFunction(string armFunctionName,
-        [NotNullWhen(true)] out JToken? result,
-        [NotNullWhen(false)] out DiagnosticBuilder.DiagnosticBuilderDelegate? builderFunc,
-        params FunctionArgument[] arguments)
+    private static ResultWithDiagnosticBuilder<JToken> EvaluateOperatorAsArmFunction(string armFunctionName, params FunctionArgument[] arguments)
     {
         try
         {
-            result = ExpressionBuiltInFunctions.Functions.EvaluateFunction(armFunctionName, arguments, new TemplateExpressionEvaluationHelper().EvaluationContext);
-            builderFunc = default;
-            return true;
+            var result = ExpressionBuiltInFunctions.Functions.EvaluateFunction(armFunctionName, arguments, new TemplateExpressionEvaluationHelper().EvaluationContext);
+            return new(result);
         }
         catch (Exception e)
         {
             // The ARM function invoked will almost certainly fail at runtime, but there's a chance a fix has been
             // deployed to ARM since this version of Bicep was released. Given that context, this failure will only
             // be reported as a warning, and the fallback type will be used.
-            builderFunc = b => b.ArmFunctionLiteralTypeConversionFailedWithMessage(
+            return new(b => b.ArmFunctionLiteralTypeConversionFailedWithMessage(
                 string.Join(", ", arguments.Select(a => a.TryGetToken()?.ToString())),
                 armFunctionName,
-                e.Message);
-            result = default;
-            return false;
+                e.Message));
         }
     }
-}
+}