Merge pull request #99 from nblumhardt/list-enumeration-index

Supply the list element index in the second #each parameter when enumerating

Author: nblumhardt

src/Serilog.Expressions/Templates/Compilation/CompiledRepetition.cs

@@ -22,22 +22,22 @@ class CompiledRepetition : CompiledTemplate
 {
     readonly Evaluatable _enumerable;
     readonly string? _keyOrElementName;
-    readonly string? _valueName;
+    readonly string? _valueOrIndexName;
     readonly CompiledTemplate _body;
     readonly CompiledTemplate? _delimiter;
     readonly CompiledTemplate? _alternative;
 
     public CompiledRepetition(
         Evaluatable enumerable,
         string? keyOrElementName,
-        string? valueName,
+        string? valueOrIndexName,
         CompiledTemplate body,
         CompiledTemplate? delimiter,
         CompiledTemplate? alternative)
     {
         _enumerable = enumerable;
         _keyOrElementName = keyOrElementName;
-        _valueName = valueName;
+        _valueOrIndexName = valueOrIndexName;
         _body = body;
         _delimiter = delimiter;
         _alternative = alternative;
@@ -52,29 +52,32 @@ public override void Evaluate(EvaluationContext ctx, TextWriter output)
             return;
         }
 
-        if (enumerable is SequenceValue sv)
+        if (enumerable is SequenceValue sequence)
         {
-            if (sv.Elements.Count == 0)
+            if (sequence.Elements.Count == 0)
             {
                 _alternative?.Evaluate(ctx, output);
                 return;
             }
 
-            var first = true;
-            foreach (var element in sv.Elements)
+            for (var i = 0; i < sequence.Elements.Count; ++i)
             {
-                if (element == null)
-                    continue; // Should have been invalid but Serilog didn't check and so this does occur in the wild.
+                // Null elements should have been invalid but Serilog didn't check, and so this does occur in the wild.
+                var element = sequence.Elements[i] ?? new ScalarValue(null);
 
-                if (first)
-                    first = false;
-                else
+                if (i != 0)
+                {
                     _delimiter?.Evaluate(ctx, output);
+                }
 
                 var local = _keyOrElementName != null
-                    ? new(ctx.LogEvent, Locals.Set(ctx.Locals, _keyOrElementName, element))
+                    ? new EvaluationContext(ctx.LogEvent, Locals.Set(ctx.Locals, _keyOrElementName, element))
                     : ctx;
 
+                local = _valueOrIndexName != null
+                    ? new EvaluationContext(local.LogEvent, Locals.Set(local.Locals, _valueOrIndexName, new ScalarValue(i)))
+                    : local;
+
                 _body.Evaluate(local, output);
             }
 
@@ -101,8 +104,8 @@ public override void Evaluate(EvaluationContext ctx, TextWriter output)
                     ? new(ctx.LogEvent, Locals.Set(ctx.Locals, _keyOrElementName, new ScalarValue(member.Name)))
                     : ctx;
 
-                local = _valueName != null
-                    ? new(local.LogEvent, Locals.Set(local.Locals, _valueName, member.Value))
+                local = _valueOrIndexName != null
+                    ? new(local.LogEvent, Locals.Set(local.Locals, _valueOrIndexName, member.Value))
                     : local;
 
                 _body.Evaluate(local, output);
@@ -129,8 +132,8 @@ public override void Evaluate(EvaluationContext ctx, TextWriter output)
                     ? new(ctx.LogEvent, Locals.Set(ctx.Locals, _keyOrElementName, element.Key))
                     : ctx;
 
-                local = _valueName != null
-                    ? new(local.LogEvent, Locals.Set(local.Locals, _valueName, element.Value))
+                local = _valueOrIndexName != null
+                    ? new(local.LogEvent, Locals.Set(local.Locals, _valueOrIndexName, element.Value))
                     : local;
 
                 _body.Evaluate(local, output);

test/Serilog.Expressions.Tests/Cases/template-evaluation-cases.asv

@@ -23,6 +23,7 @@ A{#if false}B{#else if false}C{#else if true}D{#else}E{#end} ⇶ AD
 A{#if false}B{#else if true}C{#end}                  ⇶ AC
 {#if true}A{#if false}B{#else}C{#end}D{#end}         ⇶ ACD
 {#each a in [1,2,3]}<{a}>{#delimit},{#end}           ⇶ <1>,<2>,<3>
+{#each a, i in [1,2,3]}<{a}>({i}){#delimit},{#end}   ⇶ <1>(0),<2>(1),<3>(2)
 {#each a in {x: 1, y: 2}}{a}{#end}                   ⇶ xy
 {#each a, b in {x: 1, y: 2}}{a}.{b}{#end}            ⇶ x.1y.2
 {#each a, b in {x: {y: 'z'}}}{#each c, d in b}A: {a}, C: {c}, D: {d}{#end}{#end} ⇶ A: x, C: y, D: z