From 1dc2ece826c4cd1959cdedbfbb47a7f08982ef46 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Tue, 2 Jul 2024 11:19:50 -0400
Subject: [PATCH] [BUG]: SelectExpressionFactory fails with empty string (#28)

* Fix check for empty select expressions

---------

Co-authored-by: Matt Edwards <matthew.edwards@wagglebee.net>
---
 .../Expressions/SelectExpressionFactory.cs    |  3 ++
 .../Query/JsonPathFilterExpressionTests.cs    | 38 +++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/src/Hyperbee.Json/Filters/Parser/Expressions/SelectExpressionFactory.cs b/src/Hyperbee.Json/Filters/Parser/Expressions/SelectExpressionFactory.cs
index ac17d6d6..195545d5 100644
--- a/src/Hyperbee.Json/Filters/Parser/Expressions/SelectExpressionFactory.cs
+++ b/src/Hyperbee.Json/Filters/Parser/Expressions/SelectExpressionFactory.cs
@@ -16,6 +16,9 @@ static class ExpressionHelper<TNode>
 
         public static Expression GetExpression( ReadOnlySpan<char> item, FilterContext<TNode> context )
         {
+            if ( item.IsEmpty )
+                return null;
+
             if ( item[0] != '$' && item[0] != '@' )
                 return null;
 
diff --git a/test/Hyperbee.Json.Tests/Query/JsonPathFilterExpressionTests.cs b/test/Hyperbee.Json.Tests/Query/JsonPathFilterExpressionTests.cs
index 1ee3663a..f5d9de69 100644
--- a/test/Hyperbee.Json.Tests/Query/JsonPathFilterExpressionTests.cs
+++ b/test/Hyperbee.Json.Tests/Query/JsonPathFilterExpressionTests.cs
@@ -489,6 +489,44 @@ public void FilterExpressionWithEqualsArrayWithSingleQuotes( string query, Type
         _ = source.Select( query ).ToArray();
     }
 
+    [DataTestMethod]
+    [DataRow( "$[?(@.a[?(@.price>10)])]", typeof( JsonDocument ) )]
+    [DataRow( "$[?(@.a[?(@.price>10)])]", typeof( JsonNode ) )]
+    [ExpectedException( typeof( NotSupportedException ) )]
+    public void FilterExpressionWithSubFilter( string query, Type sourceType )
+    {
+        // consensus: NOT_SUPPORTED
+
+        var json =
+            """
+            [
+                {
+                    "a": [{"price": 1}, {"price": 3}]
+                },
+                {
+                    "a": [{"price": 11}]
+                },
+                {
+                    "a": [{"price": 8}, {"price": 12}, {"price": 3}]
+                },
+                {
+                    "a": []
+                }
+            ]
+            """;
+
+        var source = GetDocumentFromSource( sourceType, json );
+
+        var matches = source.Select( query );
+        var expected = new[]
+        {
+            source.FromJsonPathPointer( "$[1]" ),
+            source.FromJsonPathPointer( "$[2]" )
+        };
+
+        Assert.IsTrue( expected.SequenceEqual( matches ) );
+    }
+
     [DataTestMethod]
     [DataRow( "$[?((@.key<44)==false)]", typeof( JsonDocument ) )]
     [DataRow( "$[?((@.key<44)==false)]", typeof( JsonNode ) )]