--sub-lang failed to download subtitles with dash in it.

[nickyfoto]

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Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2019.04.07. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

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• At least skimmed through the README, most notably the FAQ and BUGS sections
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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

Add the -v flag to your command line you run youtube-dl with (youtube-dl -v <your command line>), copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

youtube-dl -v --sub-lang pt-BR --write-auto-sub --skip-download https://www.youtube.com/watch\?v\=lmWh9jV_1ac
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'--sub-lang', u'pt-BR', u'--write-auto-sub', u'--skip-download', u'https://www.youtube.com/watch?v=lmWh9jV_1ac']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.04.07
[debug] Python version 2.7.15 (CPython) - Darwin-18.5.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 4.1.2, ffprobe 4.1.2, rtmpdump 2.4
[debug] Proxy map: {}
[youtube] lmWh9jV_1ac: Downloading webpage
[youtube] lmWh9jV_1ac: Downloading video info webpage
[youtube] lmWh9jV_1ac: Looking for automatic captions
WARNING: pt-BR subtitles not available for lmWh9jV_1ac
[debug] Default format spec: bestvideo+bestaudio/best
...
<end of log>

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Description of your issue, suggested solution and other information

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After listing the available subtitles, we can only download the ones without the dash in the middle such as en, es. Failed in downloading zh-CN, pt-BR or similar ones. Command report WARNING: zh-CN subtitles not available .

youtube-dl --all-subs --skip-download https://www.youtube.com/watch\?v\=lmWh9jV_1ac can correctly download all the subtitiles.

# list available subtitles
youtube-dl --list-subs https://www.youtube.com/watch?v=lmWh9jV_1ac
Available subtitles for lmWh9jV_1ac:
Language formats
vi       vtt, ttml, srv3, srv2, srv1
ru       vtt, ttml, srv3, srv2, srv1
fr       vtt, ttml, srv3, srv2, srv1
en       vtt, ttml, srv3, srv2, srv1
pt       vtt, ttml, srv3, srv2, srv1
fa       vtt, ttml, srv3, srv2, srv1
pt-PT    vtt, ttml, srv3, srv2, srv1
zh-TW    vtt, ttml, srv3, srv2, srv1
ko       vtt, ttml, srv3, srv2, srv1
it       vtt, ttml, srv3, srv2, srv1
iw       vtt, ttml, srv3, srv2, srv1
zh-CN    vtt, ttml, srv3, srv2, srv1
ar       vtt, ttml, srv3, srv2, srv1
pt-BR    vtt, ttml, srv3, srv2, srv1
es       vtt, ttml, srv3, srv2, srv1
th       vtt, ttml, srv3, srv2, srv1
sr       vtt, ttml, srv3, srv2, srv1
es-ES    vtt, ttml, srv3, srv2, srv1
ja       vtt, ttml, srv3, srv2, srv1
pl       vtt, ttml, srv3, srv2, srv1

# success

youtube-dl --sub-lang en --write-auto-sub --skip-download  https://www.youtube.com/watch?v=lmWh9jV_1ac
[youtube] lmWh9jV_1ac: Downloading webpage
[youtube] lmWh9jV_1ac: Downloading video info webpage
[youtube] lmWh9jV_1ac: Looking for automatic captions
[info] Writing video subtitles to: How do tornadoes form - James Spann-lmWh9jV_1ac.en.vtt

# success

youtube-dl --sub-lang es --write-auto-sub --skip-download  https://www.youtube.com/watch?v=lmWh9jV_1ac
[youtube] lmWh9jV_1ac: Downloading webpage
[youtube] lmWh9jV_1ac: Downloading video info webpage
[youtube] lmWh9jV_1ac: Looking for automatic captions
[info] Writing video subtitles to: How do tornadoes form - James Spann-lmWh9jV_1ac.es.vtt

# failed

youtube-dl --sub-lang zh-CN --write-auto-sub --skip-download  https://www.youtube.com/watch?v=lmWh9jV_1ac
[youtube] lmWh9jV_1ac: Downloading webpage
[youtube] lmWh9jV_1ac: Downloading video info webpage
[youtube] lmWh9jV_1ac: Looking for automatic captions
WARNING: zh-CN subtitles not available for lmWh9jV_1ac

# failed

youtube-dl --sub-lang pr-BR --write-auto-sub --skip-download  https://www.youtube.com/watch?v=lmWh9jV_1ac
[youtube] lmWh9jV_1ac: Downloading webpage
[youtube] lmWh9jV_1ac: Downloading video info webpage
[youtube] lmWh9jV_1ac: Looking for automatic captions
WARNING: pr-BR subtitles not available for lmWh9jV_1ac

[nickyfoto]

I confuse --write-sub with --write-auto-sub issue closed.