stride3d/stride · error · SemanticErrorException

While parsing a flow mapping, did not find expected ',' or…

Error message

While parsing a flow mapping,  did not find expected ',' or '}'.

What it means

YAML parser error in Parser.ParseFlowMappingKey: inside a flow mapping ({...}), after the first key the next token was neither a comma (FlowEntry) nor the closing brace, so the parser cannot continue the flow mapping. Caused by malformed flow-mapping syntax such as a missing comma between entries or an unexpected token.

Solutions

1. Add the missing ',' between flow mapping entries
2. Close the mapping with '}' where intended
3. Remove stray characters/tokens inside the flow mapping

Example fix

// before
limits: {cpu: 2 memory: 4Gi
// after
limits: {cpu: 2, memory: 4Gi}

// Reject flow mappings with obviously missing separators before load
var lines = yamlText.Split('\n'); foreach (var l in lines) if (System.Text.RegularExpressions.Regex.IsMatch(l, "\\{[^}]*\\w\\s+\\w+\\s*[^,:}\\n]")) throw new FormatException("Possible missing ',' in flow mapping: " + l);

try { yaml.Load(reader); } catch (YamlException ex) { throw new ConfigFormatException($"Flow mapping error at {ex.Start.Line}:{ex.Start.Column}"); }

When it happens

Trigger: A flow mapping like {a: 1 b: 2} (missing comma between pairs), an unclosed '{', or an illegal token inside { ... }.

Common situations: Inline JSON-ish YAML objects in config files where a comma was dropped or the closing '}' was deleted during editing.

Related errors

• While parsing a flow sequence, did not find expected ',' or…
• While parsing a block mapping, did not find expected key.
• Expected ' ', got ' ' (at line , character ).
• Did not find expected <stream-start>.
• Did not find expected

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/ae3f3d53ab431cb3. Report an issue: GitHub.

Appendix: source

Thrown at sources/core/Stride.Core.Yaml/Parser.cs:894

        {
            if (isFirst)
            {
                GetCurrentToken();
                Skip();
            }

            if (!(GetCurrentToken() is FlowMappingEnd))
            {
                if (!isFirst)
                {
                    if (GetCurrentToken() is FlowEntry)
                    {
                        Skip();
                    }
                    else
                    {
                        var current = GetCurrentToken();
                        throw new SemanticErrorException(current.Start, current.End, "While parsing a flow mapping,  did not find expected ',' or '}'.");
                    }
                }

                if (GetCurrentToken() is Key)
                {
                    Skip();

                    if (!(GetCurrentToken() is Value || GetCurrentToken() is FlowEntry || GetCurrentToken() is FlowMappingEnd))
                    {
                        states.Push(ParserState.YAML_PARSE_FLOW_MAPPING_VALUE_STATE);
                        return ParseNode(false, false);
                    }
                    else
                    {
                        state = ParserState.YAML_PARSE_FLOW_MAPPING_VALUE_STATE;
                        return ProcessEmptyScalar(GetCurrentToken().Start);
                    }
                }

View on GitHub (pinned to 96fad776d2)