Extra syntax conflict

[tatref]

Bug Report

When defining extra_syntaxes in config.toml, standard highlighters no longer work.

Environment

Zola version: 0.13, also tested master and next branches (2021-01-14).

This was working with the next branch some days ago (not sure about the exact date though..)

Step to reproduce

Test article. py3 is a standard language. shell-session is a custom language, defined in syntaxes/shell-session.sublime-syntax

+++
title = "highlight"
slug = "highlight"

date = 2099-01-01

draft = true

[taxonomies]
tags = ["test"]
+++

```py3
python = "python"
```

```shell-session
$ echo shell
```

1st test case: here I set extra_syntaxes in cargo.toml:

[markdown]
extra_syntaxes = ["syntaxes"]
highlight_code = true

Result:

Note that the python code is node highlighted, that's the issue

2nd test case: extra_syntaxes is commented:

[markdown]
#extra_syntaxes = ["syntaxes"]
highlight_code = true

The python code is now properly highlighted.

If you want to reproduce, here is the shell-session.sublime-syntax (disclaimer: it's just a quick and dirty hack...)

%YAML 1.2
---
file_extensions:
  - shell-session
scope: source.test

contexts:
  main:
    - match: "^((?:\\(.*?\\) )?[^ ]*(?:\\$|#|>))( .*)?"
    #           ^^^^^^^^^^^^^^ python venv
    #                          ^^^^ user@hostname
    #                               ^^^^^^^^^^^^ last prompt character
    #                                           ^^^^^ command
      captures:
        1: constant.prompt
        2: keyword.command

[Keats]

Looks like the extra -> default syntax fallback is not working well

[southerntofu]

@tatref what do you think of this patch instead?

I think the logical error was there: when there are some extra syntaxes, only those were looked up, not the theme.

[southerntofu]

unrelated, but there seems to be some hardcoded config.markdown.extra_syntaxes which could lead to unexpected issues like #1299. i'd be happy to fix those hardcoded paths (until removal of config.extra_syntaxes) on my branch there if it can help

[tatref]

Yes, your patch is semantically more correct.

Something else related to highlighting: what do you think about emitting warnings is the language is not found? (so if fallback to plaintext)

[southerntofu]

Yes (...) emitting warnings

Ok i opened #1312 with such warnings. What do you think?

unrelated, but there seems to be some hardcoded

My bad it looks OK actually :)

[tomholford]

Was able to checkout and build the next branch and successfully serve a site that has an extra_syntaxes key in the config 👍

edit:
@Keats Are there any plans to ship next as 0.13.1 or 0.14.0?

[Chaostheorie]

@tomholford see #1529