Changed the expression tokenizer to recognize dots in field chains

Author: Bart Koelman

src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryExpressionParser.cs

@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using System.Text;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Resources.Annotations;
@@ -31,17 +32,42 @@ protected virtual void Tokenize(string source)
 
     protected ResourceFieldChainExpression ParseFieldChain(FieldChainRequirements chainRequirements, string? alternativeErrorMessage)
     {
-        if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+        var pathBuilder = new StringBuilder();
+        EatFieldChain(pathBuilder, alternativeErrorMessage);
+
+        IImmutableList<ResourceFieldAttribute> chain = OnResolveFieldChain(pathBuilder.ToString(), chainRequirements);
+
+        if (chain.Any())
         {
-            IImmutableList<ResourceFieldAttribute> chain = OnResolveFieldChain(token.Value!, chainRequirements);
+            return new ResourceFieldChainExpression(chain);
+        }
+
+        throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
+    }
 
-            if (chain.Any())
+    private void EatFieldChain(StringBuilder pathBuilder, string? alternativeErrorMessage)
+    {
+        while (true)
+        {
+            if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+            {
+                pathBuilder.Append(token.Value);
+
+                if (TokenStack.TryPeek(out Token? nextToken) && nextToken.Kind == TokenKind.Period)
+                {
+                    EatSingleCharacterToken(TokenKind.Period);
+                    pathBuilder.Append('.');
+                }
+                else
+                {
+                    return;
+                }
+            }
+            else
             {
-                return new ResourceFieldChainExpression(chain);
+                throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
             }
         }
-
-        throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
     }
 
     protected CountExpression? TryParseCount()

src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryTokenizer.cs

@@ -14,6 +14,7 @@ public sealed class QueryTokenizer
             [')'] = TokenKind.CloseParen,
             ['['] = TokenKind.OpenBracket,
             [']'] = TokenKind.CloseBracket,
+            ['.'] = TokenKind.Period,
             [','] = TokenKind.Comma,
             [':'] = TokenKind.Colon,
             ['-'] = TokenKind.Minus

src/JsonApiDotNetCore/Queries/Internal/Parsing/TokenKind.cs

@@ -6,6 +6,7 @@ public enum TokenKind
     CloseParen,
     OpenBracket,
     CloseBracket,
+    Period,
     Comma,
     Colon,
     Minus,

test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs

@@ -54,6 +54,7 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("includes", " ", "Unexpected whitespace.")]
     [InlineData("includes", ",", "Relationship name expected.")]
     [InlineData("includes", "posts,", "Relationship name expected.")]
+    [InlineData("includes", "posts.", "Relationship name expected.")]
     [InlineData("includes", "posts[", ", expected.")]
     [InlineData("includes", "title", "Relationship 'title' does not exist on resource type 'blogs'.")]
     [InlineData("includes", "posts.comments.publishTime,",

test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/LegacyFilterParseTests.cs

@@ -31,7 +31,6 @@ public LegacyFilterParseTests()
     [InlineData("filter", "some", "Expected field name between brackets in filter parameter name.")]
     [InlineData("filter[", "some", "Expected field name between brackets in filter parameter name.")]
     [InlineData("filter[]", "some", "Expected field name between brackets in filter parameter name.")]
-    [InlineData("filter[.]", "some", "Relationship '' in '.' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[some]", "other", "Field 'some' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[author]", "some", "Attribute 'author' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[author.posts]", "some",

test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SparseFieldSetParseTests.cs

@@ -58,7 +58,7 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("fields[]", "", "Resource type expected.")]
     [InlineData("fields[ ]", "", "Unexpected whitespace.")]
     [InlineData("fields[owner]", "", "Resource type 'owner' does not exist.")]
-    [InlineData("fields[owner.posts]", "id", "Resource type 'owner.posts' does not exist.")]
+    [InlineData("fields[owner.posts]", "id", "Resource type 'owner' does not exist.")]
     [InlineData("fields[blogPosts]", " ", "Unexpected whitespace.")]
     [InlineData("fields[blogPosts]", "some", "Field 'some' does not exist on resource type 'blogPosts'.")]
     [InlineData("fields[blogPosts]", "id,owner.name", "Field 'owner.name' does not exist on resource type 'blogPosts'.")]