[*chan] Add text-posts opt (generic text-tweets)

[wlritchi]

The Twitter extractor has a text-tweets option, which causes it to return Directory results even for tweets with no media. Some other extractors (such as Patreon) behave this way by default. Still others skip non-media posts entirely. This PR adds a text-posts option to (some of?) the extractors that otherwise skip non-media posts, and updates the Twitter extractor to respect this new option alongside the existing Twitter-specific one.

I did a cursory search for common patterns (if not files and the like) that I expected might appear in extractors that skipped non-media posts. The only ones I found were the *chan extractors. The logic change is broadly similar in all of them: move the Directory result inside the loop over posts rather than just one per thread.

This change probably isn't meaningful without corresponding post-processor config for each extractor. I tested with the following config additions:

...
    "postprocessors": [
        {
            "name": "metadata",
            "event": "post",
            "filename": "{no}.post_data.json",
            "whitelist": ["2chan", "4chan", "420chan", "vichan"]
        },
        {
            "name": "metadata",
            "event": "post",
            "filename": "{postId}.post_data.json",
            "whitelist": ["8chan", "lynxchan"]
        }
    ]

420chan appears to be permanently offline, so no test results for that one. For the rest, I found threads with some text-only posts¹ and manually tested. Everything seems to work as I expected.

This change was requested in #570 (comment). The ticket itself appears to be about Twitter; should that one be closed as completed? (regardless of this PR)

Footnotes

1. Which was a rather unpleasant task for some of these sites. ↩

[wlritchi]

Mmm, further testing suggests that actually the dict update changes in lynxchan and 8chan extractors aren't right; it looks like the threadId is overwriting the postId. Will investigate further. Resolved, a logic change that I thought was necessary in these extractors actually had some incorrect assumptions. Reverted, and squashed/force-pushed to keep git blame clean for the affected lines.

[wlritchi]

Oh, and if #3447 is merged, that extractor will need a similar change to the ones here.

[Scripter17]

This seems to not work with --write-metadata

[mikf]

--write-metadata only write per-file metadata, while the metadata returned here is per-post. You'd need an "event": "post" metadata post processor to make use of it.

[Scripter17]

Sorry for not being clear

Adding --write-metadata stops the post-processor from working. Which I assume is not the intended behaviour

[mikf]

--write-metadata will overwrite post-processors defined at the top level of your config, but anything in extractor or a site category should be unaffected.

{
    "postprocessors": [{"name": "mtime"}],
    "extractor": {
        "postprocessors": [{"name": "ugoira"}],
        "4chan": {
            "postprocessors": [{"name": "compare"}]
        }
    }
}

$ gallery-dl -c config.json -v https://boards.4chan.org/tg/thread/15396072/
[4chan][debug] Active postprocessor modules: [ComparePP, UgoiraPP, MtimePP]

$ gallery-dl -c config.json -v --write-metadata https://boards.4chan.org/tg/thread/15396072/
[4chan][debug] Active postprocessor modules: [ComparePP, UgoiraPP, MetadataPP]

[Scripter17]

1. That should probably be changed/raise a warning
2. After I got it working, it seems lynxchan posts are all put in different folders instead of one per-thread folder. This happens with and without the postprocessor and --write-metadata

[Wiiplay123]

After I got it working, it seems lynxchan posts are all put in different folders instead of one per-thread folder. This happens with and without the postprocessor and --write-metadata

The extra Directory messages are updating the directory for every post in the thread.

By default, the directory is set to threadId + the text in the post, which wasn't a problem when the directory was only updated for the first post. Now it's making folders with the original thread ID + the text of the current post. The metadata filename for the text post itself gets weird and ends up having the thread ID + the most recent image filename, or just "metadata" if there is none.

[Wiiplay123]

I made an experimental commit for Lynxchan only, but it's just the bare minimum to make it work.
Is there already a way to trigger saving metadata without updating the directory? I uncommented Message.Metadata and made an extra function to do that in my version.

Wiiplay123@db8aece

As with wlritchi's version, it needs the postprocessor event in gallery-dl.conf set to "post". To keep the old metadata from being duplicated, I used this filename: "{postId}{num:?-//} {filename|subject|message[:50]}{extension:?['.'/]/}.json"

For posts with files, the filenames should be identical to the old ones. For posts without files, the format will be like the default folder filename.