Fix for range limits

Fixes #9120
sebastienros · Apr 10, 2021 · f31ed36 · f31ed36
1 parent a990d02
commit f31ed36
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Showing 2 changed files with 78 additions and 21 deletions.
diff --git a/Fluid.Tests/ForStatementTests.cs b/Fluid.Tests/ForStatementTests.cs
@@ -345,6 +345,69 @@ public async Task ForEvaluatesMemberOptionsOffsetOnly()
 
             Assert.Equal("54", sw.ToString());
         }
+
+        [Fact]
+        public async Task NegativeTargetShouldNotRenderLoop()
+        {
+            var e = new ForStatement(
+                new List<Statement> { new TextSpanStatement("x") },
+                "i",
+                new RangeExpression(
+                    new LiteralExpression(NumberValue.Create(0)),
+                    new LiteralExpression(NumberValue.Create(-1))
+                ),
+                null, null, false
+            );
+
+            var sw = new StringWriter();
+            await e.WriteToAsync(sw, HtmlEncoder.Default, new TemplateContext());
+
+            Assert.Equal("", sw.ToString());
+        }
+
+        [Fact]
+        public async Task InvalidRangeShouldNotRenderLoop()
+        {
+            var e = new ForStatement(
+                new List<Statement> { new TextSpanStatement("x") },
+                "i",
+                new RangeExpression(
+                    new LiteralExpression(NumberValue.Create(-10)),
+                    new LiteralExpression(NumberValue.Create(-20))
+                ),
+                null, null, false
+            );
+
+            var sw = new StringWriter();
+            await e.WriteToAsync(sw, HtmlEncoder.Default, new TemplateContext());
+
+            Assert.Equal("", sw.ToString());
+        }
+
+        [Fact]
+        public async Task NegativeLimitShouldStripFromEnd()
+        {
+            var context = new TemplateContext()
+                    .SetValue("limit", -3)
+                ;
+
+            var e = new ForStatement(
+                new List<Statement> { CreateMemberStatement("i") },
+                "i",
+                new RangeExpression(
+                    new LiteralExpression(NumberValue.Create(1)),
+                    new LiteralExpression(NumberValue.Create(9))
+                ),
+                new MemberExpression(new IdentifierSegment("limit")),
+                offset: null,
+                false
+            );
+
+            var sw = new StringWriter();
+            await e.WriteToAsync(sw, HtmlEncoder.Default, context);
+
+            Assert.Equal("123456", sw.ToString());
+        }
 
         static Statement CreateMemberStatement(string p)
         {

diff --git a/Fluid/Ast/ForStatement.cs b/Fluid/Ast/ForStatement.cs
@@ -54,9 +54,6 @@ public ForStatement(
         public bool Reversed { get; }
         public Statement Else { get; }
 
-        private List<FluidValue> _rangeElements;
-        private int _rangeStart, _rangeEnd;
-
         public override async ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
         {
             List<FluidValue> list = null;
@@ -68,26 +65,14 @@ public override async ValueTask<Completion> WriteToAsync(TextWriter writer, Text
             }
             else if (Range != null)
             {
-                int start = Convert.ToInt32((await Range.From.EvaluateAsync(context)).ToNumberValue());
-                int end = Convert.ToInt32((await Range.To.EvaluateAsync(context)).ToNumberValue());
+                var start = Convert.ToInt32((await Range.From.EvaluateAsync(context)).ToNumberValue());
+                var end = Convert.ToInt32((await Range.To.EvaluateAsync(context)).ToNumberValue());
 
-                // Cache range
-                if (_rangeElements == null || _rangeStart != start || _rangeEnd != end)
-                {
-                    _rangeElements = new List<FluidValue>(end - start);
+                list = new List<FluidValue>(Math.Max(1, end - start));
 
-                    for (var i = start; i <= end; i++)
-                    {
-                        _rangeElements.Add(NumberValue.Create(i));
-                    }
-
-                    list = _rangeElements;
-                    _rangeStart = start;
-                    _rangeEnd = end;
-                }
-                else
+                for (var i = start; i <= end; i++)
                 {
-                    list = _rangeElements;
+                    list.Add(NumberValue.Create(i));
                 }
             }
 
@@ -113,7 +98,16 @@ public override async ValueTask<Completion> WriteToAsync(TextWriter writer, Text
             if (Limit is not null)
             {
                 var limit = (int) (await Limit.EvaluateAsync(context)).ToNumberValue();
-                count = Math.Min(count, limit);
+
+                // Limit can be negative
+                if (limit >= 0)
+                {
+                    count = Math.Min(count, limit);
+                }
+                else
+                {
+                    count = Math.Max(0, count + limit);
+                }
             }
 
             if (count == 0)