The use of the #widget keyword (introduced by https://www.mediawiki.org/wiki/Extension:Widgets) makes Parsoid worker die.
Here for example with a git master (98387c2e8f3e5512045c0f762fca728795ebead0) and this wikicode:
{{#widget:foobar}}I get
ApiRequest { method: 'POST',
form:
{ format: 'json',
action: 'expandtemplates',
prop: 'wikitext|categories',
text: '{{#widget:foobar}}',
title: 'Main_Page' },
followRedirect: true,
uri: 'http://devwiki.wikimedia.org.uk/w/api.php',
timeout: 30000,
proxy: undefined,
strictSSL: true,
headers: { 'User-Agent': 'Parsoid/0.1', Connection: 'close' } }
[fatal][devwiki/Main_Page?oldid=156] Cannot read property 'length' of undefined
TypeError: Cannot read property 'length' of undefined
at peg$c379 (eval at <anonymous> (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:89:38), <anonymous>:1356:61)
at peg$parseeof (eval at <anonymous> (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:89:38), <anonymous>:14738:12)
at peg$parsetlb (eval at <anonymous> (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:89:38), <anonymous>:2007:12)
at peg$parsetoplevelblock (eval at <anonymous> (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:89:38), <anonymous>:1909:12)
at Object.parse (eval at <anonymous> (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:89:38), <anonymous>:17872:18)
at PegTokenizer.tokenizeAsync (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:206:24)
at PegTokenizer._processText (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:180:8)
at PegTokenizer.process (/var/www/parsoid/lib/mediawiki.tokenizer.peg.js:119:7)
at ParserPipeline.process (/var/www/parsoid/lib/mediawiki.parser.js:485:21)
at Object.Util.processContentInPipeline (/var/www/parsoid/lib/mediawiki.Util.js:1112:12)
[warning][master][15113] worker 15465 died (1), restarting.Version: unspecified
Severity: major