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Replace deprecated 'error-chain' with 'thiserror' #1820

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merged 4 commits into from
Aug 26, 2021
Merged

Replace deprecated 'error-chain' with 'thiserror' #1820

merged 4 commits into from
Aug 26, 2021

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Enselic
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@Enselic Enselic commented Aug 25, 2021 •
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We currently depend on error-chain. But error-chain has been deprecated:

So I think getting rid of error-chain will not be controversial. Exactly HOW to get rid of error-chain might be a bit controversial though. To get the discussion started, I here have a proposal on how to do it, which uses thiserror.

I did consider using anyhow, but read somewhere that someone thought that libraries should not use any particular high-level error handling library, but instead let apps pick one, and I thought that made sense. thiserror is just a derive-macro so one does not have to implement Error traits manually.

I have not done broad verification yet, but all regression tests pass, and basic error reporting work as before. Examples:

% for bat in bat bat-pr; do BAT_PAGER=bat $bat examples/simple.rs; done
[bat error]: Use of bat as a pager is disallowed in order to avoid infinite recursion problems
[bat error]: Use of bat as a pager is disallowed in order to avoid infinite recursion problems

% for bat in bat bat-pr; do BAT_PAGER='not parsable"' $bat examples/simple.rs; done 
[bat error]: Could not parse pager command.
[bat error]: Could not parse pager command.

% for bat in bat bat-pr; do $bat --language swedish tests/examples/single-line.txt; done
[bat error]: unknown syntax: 'swedish'
[bat error]: unknown syntax: 'swedish'

% echo --garbage > /home/martin/.config/bat/config
% for bat in bat bat-pr; do $bat tests/examples/single-line.txt; done
error: Found argument '--garbage' which wasn't expected, or isn't valid in this context

USAGE:
    bat [OPTIONS] [FILE]...
    bat <SUBCOMMAND>

For more information try --help
error: Found argument '--garbage' which wasn't expected, or isn't valid in this context

USAGE:
    bat-f85419fab6 [OPTIONS] [FILE]...
    bat-f85419fab6 <SUBCOMMAND>

For more information try --help

@Enselic Enselic force-pushed the replace-error-chain-with-anyhow branch from f85419f to 571e9f7 Compare August 25, 2021 07:22
@Enselic
Remove TODO on Msg(String)
d23a55d 
The reason is simply that String does not implement Error, and that would
not be a good idea. See e.g.:
https://internals.rust-lang.org/t/impl-error-for-string/8881
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sharkdp commented Aug 25, 2021

I was never really happy with this .chain_err(|| …) code, so this looks very good to me!

My understanding is that thiserror is for libraries while anyhow is for applications, yes.

We're using thiserror+anyhow in another project of mine (hexyl) which is split into library + application parts.
And we're using anyhow in fd (which is only an application).

I was quite happy with both crates so far.

sharkdp
sharkdp reviewed Aug 25, 2021
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src/error.rs
ParseIntError(::std::num::ParseIntError);
GlobParsingError(::globset::Error);
SerdeYamlError(::serde_yaml::Error);
#[derive(Error, Debug)]
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I don't understand what clippys problem is here...

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Most likely caused by thiserror allowing some clippy problems that our MSRV does not know about: https://github.com/dtolnay/thiserror/blob/master/impl/src/expand.rs#L120

Best way to fix is probably to --allow clippy::unknown_clippy_lints on MSRV clippy

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...or make use of clippy::msrv (thanks for the ping)

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I ended up using --allow clippy::unknown_clippy_lints since starting to use clippy::msrv is not trivial (requires moving to some other CI job)

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Enselic commented Aug 26, 2021

I've now fixed remaining open issue and done some additional verification, and the code seems to work as it should.

So feel free to take another look. If it looks good, we can (squash) merge this, as far as I'm concerned.

@Enselic Enselic requested a review from sharkdp August 26, 2021 07:10
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sharkdp approved these changes Aug 26, 2021
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Thanks!

@Enselic Enselic merged commit 19c3e82 into sharkdp:master Aug 26, 2021
@Enselic Enselic deleted the replace-error-chain-with-anyhow branch August 26, 2021 11:12
@Enselic Enselic mentioned this pull request Oct 4, 2021
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@Enselic Enselic mentioned this pull request Jan 17, 2022
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