Analysis: macro call with unparing << > freezes UI on TiddlyWiki 5.4 — root cause and quick fix

[linonetwo]

I investigated a case where the tag-tree-picker plugin caused the browser tab to freeze on TiddlyWiki 5.4-prerelease. After manual reproducing, AI found this was triggered by a syntax bug in my plugin’s macro output rather than a bug in core.

• The plugin’s tagTreeMacro generated macro calls like colourB=<<colourB> (single >), repeated for each tag (~26 items in the test data).
• TiddlyWiki 5.4’s parser handles macro-parameter parsing differently (sticky regex /y and stricter attribute parsing). For the malformed colourB=<<colourB> the parser produced a malformed attribute map (an extra attribute named <<colourB and colourB parsed as a string), which led to bad parse trees and ultimately a render-time crash/freeze.
• TiddlyWiki 5.3 tolerated that malformed form in a way that avoided the crash; the stricter 5.4 behavior exposed the plugin’s syntax error.

The plugin emits malformed macro syntax (colourB=<<colourB> instead of colourB=<<colourB>>). This is a plugin-side bug. But the change in TiddlyWiki 5.4’s parser made that malformed syntax produce an invalid parse tree that leads to render-time instability. So I post it here so other plugin authors could find how to fix freezing bug.

[saqimtiaz]

@Jermolene this may unfortunately be a blocker for the release.

[Jermolene]

Ouch yes, not good. I'll investigate further

[linonetwo]

Do you think so? It could be easily fixed by plugin author, and missing closing > is user's fault.

[pmario]

It's not the first problem that we had to fix with new parser behaviour. There have been some changes, so the code is not as "battle tested" as it was. IMO it's actually a good thing that it came up early.

As a side effect it pointed out a bug on your side ;)