Empty message in mermaid sequence diagram not working

[ls-bit]

Mermaid allows sequence diagrams to contain empty messages. For an empty message just a whitespace is added instead of text. It should render a line without text. GitHub handles this correctly:

sequenceDiagram
    Alice->>John: Hello
    John-->>Alice: 

Loading

Kroki throws an error for the same diagram:

Error 400: Error: Syntax error in graph: Parse error on line 5: ...! John-->>-Alice: ----------------------^ Expecting 'NEWLINE', 'AS', ',', 'SOLID_OPEN_ARROW', 'DOTTED_OPEN_ARROW', 'SOLID_ARROW', 'BIDIRECTIONAL_SOLID_ARROW', 'DOTTED_ARROW', 'BIDIRECTIONAL_DOTTED_ARROW', 'SOLID_CROSS', 'DOTTED_CROSS', 'SOLID_POINT', 'DOTTED_POINT', 'TXT', got 'INVALID' Error: Parse error on line 5: ...! John-->>-Alice: ----------------------^ Expecting 'NEWLINE', 'AS', ',', 'SOLID_OPEN_ARROW', 'DOTTED_OPEN_ARROW', 'SOLID_ARROW', 'BIDIRECTIONAL_SOLID_ARROW', 'DOTTED_ARROW', 'BIDIRECTIONAL_DOTTED_ARROW', 'SOLID_CROSS', 'DOTTED_CROSS', 'SOLID_POINT', 'DOTTED_POINT', 'TXT', got 'INVALID' at Ot.parseError (file:///usr/local/kroki/assets/mermaid/chunks/mermaid.esm.min/sequenceDiagram-7SUASMRF.mjs:1:14208) at Ot.parse (file:///usr/local/kroki/assets/mermaid/chunks/mermaid.esm.min/sequenceDiagram-7SUASMRF.mjs:3:174) at Diagram.fromText (file:///usr/local/kroki/assets/mermaid/mermaid.esm.min.mjs:3:253) at async Object.render (file:///usr/local/kroki/assets/mermaid/mermaid.esm.min.mjs:10:1164)

https://kroki.io/mermaid/svg/eNorTi0sTc1LTnXJTEwvSszlUgACx5zM5FRdOzuv_Iw8KwWP1JycfLA4iK8LFAfLWykAAEB5EiQ=

If the empty message is not the last line it also works in Kroki:

sequenceDiagram
    Alice->>John: Hello
    John-->>Alice: 
    John->>Alice: Hello

Loading

https://kroki.io/mermaid/svg/eNorTi0sTc1LTnXJTEwvSszlUgACx5zM5FRdOzuv_Iw8KwWP1JycfLA4iK8LFAfLWylgE0sBAPLhF68=

Maybe this happens due to input being trimmed somewhere.

[ggrossetie]

It seems to be related to how we encode/decode the diagram. It's working fine if I send the diagram using a POST request: https://docs.kroki.io/kroki/setup/usage/

[ggrossetie]

One way to workaround this limitation is to add an empty comment (in order to preserve the trailing spaces):

sequenceDiagram
    Alice->>John: Hello
    John-->>Alice: 
%%