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feat: extract delegate body from UseProvidedBody syntax for source generation
Add DelegateBodySyntaxExtractor to extract lambda body from syntax tree. Support both expression lambdas (e.g. () => 42) and block lambdas with complex control flow (if/else, switch, multi-statement bodies). Add EmitWithBody to PartialMethodSourceEmitter for arbitrary body emission. Fix test lambda parameter names to match actual method parameters. Co-authored-by: dex3r <3155725+dex3r@users.noreply.github.com> Agent-Logs-Url: https://github.com/dex3r/EasySourceGenerators/sessions/e1b5542a-d819-423d-a4b7-f97407a7d1b4
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6 files changed

Lines changed: 229 additions & 11 deletions

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‎EasySourceGenerators.Generators/IncrementalGenerators/DelegateBodySyntaxExtractor.cs‎

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@@ -0,0 +1,157 @@
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using System;
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using System.Linq;
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using System.Text;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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namespace EasySourceGenerators.Generators.IncrementalGenerators;
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/// <summary>
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/// Extracts the delegate body source code from a <c>UseProvidedBody(...)</c> invocation
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/// within a generator method's syntax tree. The extracted body is re-indented to match
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/// the target method body indentation (8 spaces).
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/// </summary>
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internal static class DelegateBodySyntaxExtractor
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{
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private const string MethodBodyIndent = " ";
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/// <summary>
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/// Attempts to find a <c>UseProvidedBody(...)</c> call in the given generator method syntax
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/// and extract the lambda body. Returns <c>null</c> if no such call is found.
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/// For expression lambdas, returns a single <c>return {expr};</c> line.
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/// For block lambdas, returns the block body re-indented to the method body level.
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/// </summary>
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internal static string? TryExtractDelegateBody(MethodDeclarationSyntax generatorMethodSyntax)
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{
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InvocationExpressionSyntax? invocation = generatorMethodSyntax
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.DescendantNodes()
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.OfType<InvocationExpressionSyntax>()
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.FirstOrDefault(inv =>
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inv.Expression is MemberAccessExpressionSyntax memberAccess &&
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memberAccess.Name.Identifier.Text == "UseProvidedBody");
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if (invocation == null)
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{
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return null;
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}
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ArgumentSyntax? argument = invocation.ArgumentList.Arguments.FirstOrDefault();
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if (argument?.Expression is not LambdaExpressionSyntax lambda)
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{
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return null;
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}
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if (lambda.Body is ExpressionSyntax expression)
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{
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string expressionText = expression.ToFullString().Trim();
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return expressionText;
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}
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if (lambda.Body is BlockSyntax block)
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{
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return ExtractBlockBody(block);
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}
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return null;
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}
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/// <summary>
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/// Extracts the content of a block body (between <c>{</c> and <c>}</c>),
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/// determines the base indentation, and re-indents all lines to the method body level.
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/// Blank lines between statements are preserved with method body indentation.
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/// </summary>
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private static string? ExtractBlockBody(BlockSyntax block)
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{
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string blockText = block.ToFullString();
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string[] lines = blockText.Replace("\r\n", "\n").Replace("\r", "\n").Split('\n');
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int openIndex = -1;
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int closeIndex = -1;
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for (int i = 0; i < lines.Length; i++)
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{
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if (openIndex == -1 && lines[i].TrimEnd().EndsWith("{", StringComparison.Ordinal))
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{
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openIndex = i;
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break;
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}
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}
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for (int i = lines.Length - 1; i >= 0; i--)
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{
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string trimmed = lines[i].Trim();
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if (trimmed.StartsWith("}", StringComparison.Ordinal))
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{
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closeIndex = i;
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break;
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}
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}
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if (openIndex == -1 || closeIndex == -1 || closeIndex <= openIndex)
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{
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return null;
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}
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string[] contentLines = new string[closeIndex - openIndex - 1];
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Array.Copy(lines, openIndex + 1, contentLines, 0, contentLines.Length);
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if (contentLines.Length == 0)
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{
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return null;
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}
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int minIndent = int.MaxValue;
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foreach (string line in contentLines)
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{
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if (string.IsNullOrWhiteSpace(line))
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{
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continue;
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}
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int indent = 0;
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foreach (char c in line)
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{
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if (c == ' ')
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{
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indent++;
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}
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else if (c == '\t')
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{
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indent += 4;
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}
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else
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{
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break;
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}
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}
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if (indent < minIndent)
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{
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minIndent = indent;
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}
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}
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if (minIndent == int.MaxValue)
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{
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minIndent = 0;
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}
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StringBuilder result = new();
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for (int i = 0; i < contentLines.Length; i++)
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{
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string line = contentLines[i];
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if (string.IsNullOrWhiteSpace(line))
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{
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result.AppendLine(MethodBodyIndent);
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}
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else
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{
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string stripped = minIndent <= line.Length ? line.Substring(minIndent) : line.TrimStart();
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string trimmedEnd = stripped.TrimEnd();
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result.AppendLine(MethodBodyIndent + trimmedEnd);
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}
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}
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return result.ToString().TrimEnd('\n', '\r');
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}
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}

‎EasySourceGenerators.Generators/IncrementalGenerators/GeneratesMethodGenerationPipeline.cs‎

Lines changed: 36 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -96,8 +96,9 @@ private static string GenerateSourceForGroup(
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}
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/// <summary>
99-
/// Generates source code from a fluent body pattern, executing the generator method
100-
/// and extracting the return value from the fluent API result.
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/// Generates source code from a fluent body pattern. First attempts to extract the delegate
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/// body from a <c>UseProvidedBody</c> call in the syntax tree. If no such call is found,
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/// falls back to executing the generator method and extracting the return value.
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/// </summary>
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private static string GenerateFromFluentBodyPattern(
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SourceProductionContext context,
@@ -106,6 +107,18 @@ private static string GenerateFromFluentBodyPattern(
106107
INamedTypeSymbol containingType,
107108
Compilation compilation)
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{
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string? delegateBody = DelegateBodySyntaxExtractor.TryExtractDelegateBody(methodInfo.Syntax);
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if (delegateBody != null)
112+
{
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bool isVoidReturn = partialMethod.ReturnType.SpecialType == SpecialType.System_Void;
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string bodyLines = FormatDelegateBodyForEmit(delegateBody, isVoidReturn);
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return GeneratesMethodPatternSourceBuilder.GeneratePartialMethodWithBody(
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containingType,
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partialMethod,
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bodyLines);
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}
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(FluentBodyResult? result, string? error) = GeneratesMethodExecutionRuntime.ExecuteFluentBodyGeneratorMethod(
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methodInfo.Symbol,
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partialMethod,
@@ -127,6 +140,27 @@ private static string GenerateFromFluentBodyPattern(
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result!.ReturnValue);
128141
}
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/// <summary>
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/// Formats the extracted delegate body for emission. Expression bodies are wrapped in
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/// <c>return {expr};</c>. Block bodies are used as-is (already re-indented by the extractor).
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/// </summary>
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private static string FormatDelegateBodyForEmit(string delegateBody, bool isVoidReturn)
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{
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bool isBlockBody = delegateBody.Contains("\n");
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if (isBlockBody)
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{
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return delegateBody;
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}
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if (isVoidReturn)
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{
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return $" {delegateBody};";
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}
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return $" return {delegateBody};";
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}
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/// <summary>
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/// Generates source code from a simple pattern, executing the generator method
132166
/// and using its return value as the partial method's return expression.

‎EasySourceGenerators.Generators/IncrementalGenerators/GeneratesMethodPatternSourceBuilder.cs‎

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@@ -28,6 +28,19 @@ internal static string GenerateSimplePartialMethod(
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return PartialMethodSourceEmitter.Emit(emitData, returnValueLiteral);
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}
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/// <summary>
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/// Generates a complete C# source file containing a partial method implementation
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/// with the given body lines (already indented to the method body level).
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/// </summary>
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internal static string GeneratePartialMethodWithBody(
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INamedTypeSymbol containingType,
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IMethodSymbol partialMethod,
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string bodyLines)
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{
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PartialMethodEmitData emitData = RoslynSymbolDataMapper.ToPartialMethodEmitData(containingType, partialMethod);
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return PartialMethodSourceEmitter.EmitWithBody(emitData, bodyLines);
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}
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/// <summary>
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/// Formats a string value as a C# literal expression based on the target return type.
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/// Delegates to <see cref="CSharpLiteralFormatter.FormatValueAsLiteral"/>.

‎EasySourceGenerators.Generators/SourceEmitting/PartialMethodSourceEmitter.cs‎

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@@ -26,6 +26,19 @@ internal static string Emit(PartialMethodEmitData data, string? returnValueLiter
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return builder.ToString();
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}
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/// <summary>
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/// Generates a complete C# source file containing a partial method implementation
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/// with the given body lines (already indented to the method body level).
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/// </summary>
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internal static string EmitWithBody(PartialMethodEmitData data, string bodyLines)
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{
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StringBuilder builder = new();
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AppendFileHeader(builder, data);
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builder.AppendLine(bodyLines);
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AppendClosingBraces(builder);
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return builder.ToString();
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}
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/// <summary>
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/// Appends the auto-generated file header, namespace declaration, type declaration,
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/// and method signature opening to the <see cref="StringBuilder"/>.

‎EasySourceGenerators.Tests/DelegateBodyTests.cs‎

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@@ -57,7 +57,7 @@ static partial class DelegateBodyTestClass_WithIf
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{
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public static partial int PartialMethod(int someParam)
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{
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if (someParamHere > 0)
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if (someParam > 0)
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{
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return 42;
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}
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{
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public static partial int PartialMethod(int someParam)
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{
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switch (someParamHere)
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switch (someParam)
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{
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case -1: return 6;
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case 0: return 7;
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{
111111
int interResult = 0;
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switch (someParamHere)
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switch (someParam)
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{
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case -1: interResult = 6; break;
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case 0: interResult = 7; break;
@@ -157,9 +157,9 @@ public static partial class DelegateBodyTestClass_WithIf
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public static IMethodBodyGenerator JustReturnConstantGenerator() =>
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Generate.MethodBody()
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.ForMethod().WithReturnType<int>().WithParameter<int>()
160-
.UseProvidedBody(someParamHere =>
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.UseProvidedBody(someParam =>
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{
162-
if (someParamHere > 0)
162+
if (someParam > 0)
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{
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return 42;
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}
@@ -178,9 +178,9 @@ public static partial class DelegateBodyTestClass_WithSwitch
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public static IMethodBodyGenerator JustReturnConstantGenerator() =>
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Generate.MethodBody()
180180
.ForMethod().WithReturnType<int>().WithParameter<int>()
181-
.UseProvidedBody(someParamHere =>
181+
.UseProvidedBody(someParam =>
182182
{
183-
switch (someParamHere)
183+
switch (someParam)
184184
{
185185
case -1: return 6;
186186
case 0: return 7;
@@ -198,11 +198,11 @@ public static partial class DelegateBodyTestClass_WithComplexBody
198198
public static IMethodBodyGenerator JustReturnConstantGenerator() =>
199199
Generate.MethodBody()
200200
.ForMethod().WithReturnType<int>().WithParameter<int>()
201-
.UseProvidedBody(someParamHere =>
201+
.UseProvidedBody(someParam =>
202202
{
203203
int interResult = 0;
204204

205-
switch (someParamHere)
205+
switch (someParam)
206206
{
207207
case -1: interResult = 6; break;
208208
case 0: interResult = 7; break;

‎EasySourceGenerators.Tests/EasySourceGenerators.Tests.csproj‎

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<ItemGroup>
2727
<Using Include="NUnit.Framework"/>
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<Using Include="System.Text"/>
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</ItemGroup>
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<PropertyGroup>

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