Fetching OTP docs fails for some functions

[robertoaloi]

• gen_server:call
• io:format

Reason:     {function_clause,[{shell_docs,get_bullet,[[l],undefined],[{file,"shell_docs.erl"},{line,779}]},{shell_docs,render_element,5,[{file,"shell_docs.erl"},{line,700}]},{lists,mapfoldl,3,[{file,"lists.erl"},{line,1354}]},{shell_docs,render_element,5,[{file,"shell_docs.erl"},{line,639}]},{lists,mapfoldl,3,[{file,"lists.erl"},{line,1354}]},{lists,mapfoldl,3,[{file,"lists.erl"},{line,1355}]},{shell_docs,render_docs,3,[{file,"shell_docs.erl"},{line,577}]},{shell_docs,render_headers_and_docs,3,[{file,"shell_docs.erl"},{line,538}]}]}
     Offender:   [{pid,<0.184.0>},{id,els_hover_provider},{mfargs,{els_provider,start_link,[els_hover_provider]}},{restart_type,permanent},{shutdown,brutal_kill},{child_type,worker}]

Other similar functions such as gen_server:cast work fine.

[alanz]

I am getting this problem too, with OTP 23.1.1. In erlang_ls.erl, I log

[info] <0.9.0>@erlang_ls:main:25 io:getopts: [[{binary,true},{encoding,latin1}]]

[alanz]

And the emergency workaround we are deploying internally is 1939063, which just disables use of the shell docs.

[garazdawi]

This has to do with trying to detect if the printing shell supports unicode in order to print nice unicode bullet-points :). The call that is made is io:getopts() which is expected to return a property list with {encoding,latin1|unicode} in it. Which process is the group_leader of the process that you are calling the render function from?

[robertoaloi]

Of course! And since for the STDIO transport we use a noop group leader, the response to a getopts request is hard-coded to an empty list:

erlang_ls/src/els_sup.erl

Line 105 in 7dcbad1

From ! {io_reply, ReplyAs, []};

[garazdawi]

I will add options to shell_docs:render so that you can control that via options instead of reading it from the group leader. I'll put it into OTP-23.2, so for releases before that you need to work with the group leader and return an encoding.

[alanz]

Of course! And since for the STDIO transport we use a noop group leader, the response to a getopts request is hard-coded to an empty list:

Could we use the original values (from the spawning process) instead?