Missing package handling and errors

[ngriffiths21]

When tinytex::parse_packages() fails to parse the tex log correctly, it leads to confusing errors.

For example, when I tried to compile the following test.Rmd with a fresh tinytex installation:

---
output: pdf_document
header-includes:
    - \usepackage{XCharter}
---

# Test file

This is a test

the following LaTeX error is logged:

! Package fontenc Error: Encoding file `t2aenc.def' not found.
(fontenc)                You might have misspelt the name of the encoding.

but tinytex parses it incorrectly, with an extra backtick:

> tinytex:::detect_files(" file `t2aenc.def' not found")
[1] "`t2aenc.def"

which leads tlmgr to search for '/`t2aenc.def' rather than '/t2aenc.def' and thus fail to identify the missing package.

At the very least, can the error be much clearer? e.g.:

LaTeX Error: [error from the log] (check file.log for more details).
Tinytex believes there is a missing package that contains the file "file.def"
Attempting to identify missing package automatically...
[tlmgr command]
Could not automatically identify missing package (see https://yihui.org/tinytex/#maintenance to try manually).

Inevitably, the regex will fail sometimes, which is fine. But it should be obvious that (1) it is a LaTeX error, NOT an rmarkdown or tinytex error, and (2) if tlmgr search fails, it's up to the user to figure out which package is missing.

(Also see item 2 in this answer (https://stackoverflow.com/a/58410965) for a similar situation when regex matched an error that wasn't actually a missing package).

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[yihui]

Should be fixed now. Thanks for the report!

> tinytex:::detect_files(" file `t2aenc.def' not found")
[1] "t2aenc.def"

I have made it clear that the error comes from LaTeX. I have also muted some messages by default, since they are not that useful in most cases (can be turned back on via options(tinytex.verbose = TRUE)).

The item 2 in https://stackoverflow.com/a/58410965 should also be fixed now. Thanks again!

[ngriffiths21]

Great, thanks so much!