Null support.

src/Squidex.Infrastructure/Queries/FilterValue.cs

@@ -123,15 +123,27 @@ namespace Squidex.Infrastructure.Queries
         {
             if (Value is IList list)
             {
-                return $"[{string.Join(", ", list.OfType<object>().ToArray())}]";
+                return $"[{string.Join(", ", list.OfType<object>().Select(ToString).ToArray())}]";
             }
-            else if (Value == null)
+            else
+            {
+                return ToString(Value);
+            }
+        }
+
+        private string ToString(object value)
+        {
+            if (ValueType == FilterValueType.String)
+            {
+                return $"'{value.ToString().Replace("'", "\\'")}'";
+            }
+            else if (value == null)
             {
-                return "<Null>";
+                return "null";
             }
             else
             {
-                return Value.ToString();
+                return value.ToString();
             }
         }
     }

src/Squidex.Infrastructure/Queries/OData/ConstantWithTypeVisitor.cs

@@ -60,6 +60,11 @@ namespace Squidex.Infrastructure.Queries.OData
                 return new FilterValue(ParseInstant(value));
             }
 
+            if (ConstantVisitor.Visit(nodeIn.Source) == null)
+            {
+                return FilterValue.Null;
+            }
+
             throw new NotSupportedException();
         }
 

src/Squidex.Infrastructure/Queries/Query.cs

@@ -32,7 +32,7 @@ namespace Squidex.Infrastructure.Queries
 
             if (FullText != null)
             {
-                parts.Add($"FullText: {FullText}");
+                parts.Add($"FullText: '{FullText.Replace("'", "\'")}'");
             }
 
             if (Skip > 0)

tests/Squidex.Domain.Apps.Entities.Tests/Assets/AssetQueryServiceTests.cs

@@ -109,7 +109,7 @@ namespace Squidex.Domain.Apps.Entities.Assets
         {
             await sut.QueryAsync(context, Q.Empty.WithODataQuery("$top=100&$orderby=fileName asc&$search=Hello World"));
 
-            A.CallTo(() => assetRepository.QueryAsync(appId, A<Query>.That.Matches(x => x.ToString() == "FullText: Hello World; Take: 100; Sort: fileName Ascending")))
+            A.CallTo(() => assetRepository.QueryAsync(appId, A<Query>.That.Matches(x => x.ToString() == "FullText: 'Hello World'; Take: 100; Sort: fileName Ascending")))
                 .MustHaveHappened();
         }
 
@@ -118,7 +118,7 @@ namespace Squidex.Domain.Apps.Entities.Assets
         {
             await sut.QueryAsync(context, Q.Empty.WithODataQuery("$filter=fileName eq 'ABC'"));
 
-            A.CallTo(() => assetRepository.QueryAsync(appId, A<Query>.That.Matches(x => x.ToString() == "Filter: fileName == ABC; Take: 200; Sort: lastModified Descending")))
+            A.CallTo(() => assetRepository.QueryAsync(appId, A<Query>.That.Matches(x => x.ToString() == "Filter: fileName == 'ABC'; Take: 200; Sort: lastModified Descending")))
                 .MustHaveHappened();
         }
 

tests/Squidex.Domain.Apps.Entities.Tests/Assets/Queries/FilterTagTransformerTests.cs

@@ -28,7 +28,7 @@ namespace Squidex.Domain.Apps.Entities.Assets.Queries
             var source = FilterBuilder.Eq("tags", "name1");
             var result = FilterTagTransformer.Transform(source, appId, tagService);
 
-            Assert.Equal("tags == id1", result.ToString());
+            Assert.Equal("tags == 'id1'", result.ToString());
         }
 
         [Fact]
@@ -40,7 +40,7 @@ namespace Squidex.Domain.Apps.Entities.Assets.Queries
             var source = FilterBuilder.Eq("tags", "name1");
             var result = FilterTagTransformer.Transform(source, appId, tagService);
 
-            Assert.Equal("tags == name1", result.ToString());
+            Assert.Equal("tags == 'name1'", result.ToString());
         }
 
         [Fact]
@@ -49,7 +49,7 @@ namespace Squidex.Domain.Apps.Entities.Assets.Queries
             var source = FilterBuilder.Eq("other", "value");
             var result = FilterTagTransformer.Transform(source, appId, tagService);
 
-            Assert.Equal("other == value", result.ToString());
+            Assert.Equal("other == 'value'", result.ToString());
 
             A.CallTo(() => tagService.GetTagIdsAsync(appId, A<string>.Ignored, A<HashSet<string>>.Ignored))
                 .MustNotHaveHappened();

tests/Squidex.Domain.Apps.Entities.Tests/Contents/Queries/FilterTagTransformerTests.cs

@@ -45,7 +45,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.Queries
             var source = FilterBuilder.Eq("data.tags2.iv", "name1");
             var result = FilterTagTransformer.Transform(source, appId, schema, tagService);
 
-            Assert.Equal("data.tags2.iv == id1", result.ToString());
+            Assert.Equal("data.tags2.iv == 'id1'", result.ToString());
         }
 
         [Fact]
@@ -57,7 +57,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.Queries
             var source = FilterBuilder.Eq("data.tags2.iv", "name1");
             var result = FilterTagTransformer.Transform(source, appId, schema, tagService);
 
-            Assert.Equal("data.tags2.iv == name1", result.ToString());
+            Assert.Equal("data.tags2.iv == 'name1'", result.ToString());
         }
 
         [Fact]
@@ -66,7 +66,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.Queries
             var source = FilterBuilder.Eq("data.tags1.iv", "value");
             var result = FilterTagTransformer.Transform(source, appId, schema, tagService);
 
-            Assert.Equal("data.tags1.iv == value", result.ToString());
+            Assert.Equal("data.tags1.iv == 'value'", result.ToString());
 
             A.CallTo(() => tagService.GetTagIdsAsync(appId, A<string>.Ignored, A<HashSet<string>>.Ignored))
                 .MustNotHaveHappened();
@@ -78,7 +78,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.Queries
             var source = FilterBuilder.Eq("data.string.iv", "value");
             var result = FilterTagTransformer.Transform(source, appId, schema, tagService);
 
-            Assert.Equal("data.string.iv == value", result.ToString());
+            Assert.Equal("data.string.iv == 'value'", result.ToString());
 
             A.CallTo(() => tagService.GetTagIdsAsync(appId, A<string>.Ignored, A<HashSet<string>>.Ignored))
                 .MustNotHaveHappened();
@@ -90,7 +90,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.Queries
             var source = FilterBuilder.Eq("no.data", "value");
             var result = FilterTagTransformer.Transform(source, appId, schema, tagService);
 
-            Assert.Equal("no.data == value", result.ToString());
+            Assert.Equal("no.data == 'value'", result.ToString());
 
             A.CallTo(() => tagService.GetTagIdsAsync(appId, A<string>.Ignored, A<HashSet<string>>.Ignored))
                 .MustNotHaveHappened();

tests/Squidex.Infrastructure.Tests/Queries/ODataConversionTests.cs

@@ -103,11 +103,20 @@ namespace Squidex.Infrastructure.Queries
             Assert.Equal(o, i);
         }
 
+        [Fact]
+        public void Should_parse_filter_when_type_is_null()
+        {
+            var i = Q("$filter=firstName eq null");
+            var o = C("Filter: firstName == null");
+
+            Assert.Equal(o, i);
+        }
+
         [Fact]
         public void Should_parse_filter_when_type_is_string()
         {
             var i = Q("$filter=firstName eq 'Dagobert'");
-            var o = C("Filter: firstName == Dagobert");
+            var o = C("Filter: firstName == 'Dagobert'");
 
             Assert.Equal(o, i);
         }
@@ -116,7 +125,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_when_type_is_string_list()
         {
             var i = Q("$filter=firstName in ('Dagobert')");
-            var o = C("Filter: firstName in [Dagobert]");
+            var o = C("Filter: firstName in ['Dagobert']");
 
             Assert.Equal(o, i);
         }
@@ -197,7 +206,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_negation()
         {
             var i = Q("$filter=not endswith(lastName, 'Duck')");
-            var o = C("Filter: !(endsWith(lastName, Duck))");
+            var o = C("Filter: !(endsWith(lastName, 'Duck'))");
 
             Assert.Equal(o, i);
         }
@@ -206,7 +215,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_startswith()
         {
             var i = Q("$filter=startswith(lastName, 'Duck')");
-            var o = C("Filter: startsWith(lastName, Duck)");
+            var o = C("Filter: startsWith(lastName, 'Duck')");
 
             Assert.Equal(o, i);
         }
@@ -215,7 +224,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_endswith()
         {
             var i = Q("$filter=endswith(lastName, 'Duck')");
-            var o = C("Filter: endsWith(lastName, Duck)");
+            var o = C("Filter: endsWith(lastName, 'Duck')");
 
             Assert.Equal(o, i);
         }
@@ -224,7 +233,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_contains()
         {
             var i = Q("$filter=contains(lastName, 'Duck')");
-            var o = C("Filter: contains(lastName, Duck)");
+            var o = C("Filter: contains(lastName, 'Duck')");
 
             Assert.Equal(o, i);
         }
@@ -233,7 +242,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_contains_to_true()
         {
             var i = Q("$filter=contains(lastName, 'Duck') eq true");
-            var o = C("Filter: contains(lastName, Duck)");
+            var o = C("Filter: contains(lastName, 'Duck')");
 
             Assert.Equal(o, i);
         }
@@ -242,7 +251,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_contains_to_false()
         {
             var i = Q("$filter=contains(lastName, 'Duck') eq false");
-            var o = C("Filter: !(contains(lastName, Duck))");
+            var o = C("Filter: !(contains(lastName, 'Duck'))");
 
             Assert.Equal(o, i);
         }
@@ -305,7 +314,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_conjunction_and_contains()
         {
             var i = Q("$filter=contains(firstName, 'Sebastian') eq false and isComicFigure eq true");
-            var o = C("Filter: (!(contains(firstName, Sebastian)) && isComicFigure == True)");
+            var o = C("Filter: (!(contains(firstName, 'Sebastian')) && isComicFigure == True)");
 
             Assert.Equal(o, i);
         }
@@ -332,7 +341,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_full_text()
         {
             var i = Q("$search=Duck");
-            var o = C("FullText: Duck");
+            var o = C("FullText: 'Duck'");
 
             Assert.Equal(o, i);
         }
@@ -341,7 +350,7 @@ namespace Squidex.Infrastructure.Queries
         public void Should_parse_filter_with_full_text_and_multiple_terms()
         {
             var i = Q("$search=Dagobert or Donald");
-            var o = C("FullText: Dagobert or Donald");
+            var o = C("FullText: 'Dagobert or Donald'");
 
             Assert.Equal(o, i);
         }
@@ -375,7 +384,7 @@ namespace Squidex.Infrastructure.Queries
 
         private static string C(string value)
         {
-            return value.Replace('\'', '"');
+            return value;
         }
 
         private static string Q(string value)