Derived from bug 51961, comment 1: Positional parameters with an '=' in them are converted to named parameters, even if the '=' is safely embedded inside a nested transclusion.
Minimal test case:
{{echo|{{echo|1=bar}}}}
To fix this, we should probably tokenize the value with appropriate flags and look at the remaining string content instead of the entire string.
Version: unspecified
Severity: normal
Change 79836 had a related patch set uploaded by Subramanya Sastry:
WIP: (Bug 52824) Improved handling of '=' char in tpl-param values
This is normally a syntactic diff only, but still annoying:
https://en.wikipedia.org/w/index.php?title=Hartsfield%E2%80%93Jackson_Atlanta_International_Airport&diff=565342506&oldid=564597913
Change 79836 merged by jenkins-bot:
(Bug 52824) Improved handling of '=' char in tpl-param values
Now deployed to production. Verified fixed on an old id of the airport pages. Also verified the fix on https://fr.wikipedia.org/wiki/Robert_Soucy?veaction=edit as per bug 51961, comment 1.