tests: misc coverage for calendar.rs, der.rs

[cpu]

I was looking at some of the open PRs on the original briansmith/webpki repo and spotted two small ones adding bits of test coverage:

• Add test coverage for der.rs briansmith/webpki#223
• Add test coverage for pre-1970 dates briansmith/webpki#215

The unit tests look good to me and more test coverage seems appealing so I've cherry-picked the original commits onto our fork and squashed each down into 1 commit per area of coverage (and fixed a couple clippy errs).

Thanks @st3fan for the original implementation! :-)

[cpu]

ci / clippy (pull_request) Failing after 14s

Ah! I keep forgetting cargo clippy locally doesn't match the CI config. I'll fix these up in a jiffy.

[codecov]

Codecov Report

Merging #71 (b2756e0) into main (e282ccb) will increase coverage by 0.25%.
The diff coverage is 100.00%.

❗ Current head b2756e0 differs from pull request most recent head 882d929. Consider uploading reports for the commit 882d929 to get more accurate results

@@            Coverage Diff             @@
##             main      #71      +/-   ##
==========================================
+ Coverage   95.08%   95.34%   +0.25%     
==========================================
  Files          13       13              
  Lines        2604     2684      +80     
==========================================
+ Hits         2476     2559      +83     
+ Misses        128      125       -3     

Impacted Files	Coverage Δ
src/calendar.rs	95.20% <100.00%> (+2.47%)	⬆️
src/der.rs	96.64% <100.00%> (+2.57%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[djc]

ci / clippy (pull_request) Failing after 14s

Ah! I keep forgetting cargo clippy locally doesn't match the CI config. I'll fix these up in a jiffy.

I forget, why is that again?

(https://twitter.com/weihanglo/status/1661680417643143169 should help, eventually.)

[cpu]

I forget, why is that again?

There's a helper script I keep forgetting to use, (mk/clippy.sh) that sets a handful of flags:

webpki/mk/clippy.sh

Lines 21 to 35 in 6a388ac

	cargo clippy \
	--target-dir=target/clippy \
	--all-features --all-targets \
	-- \
	--deny missing_docs \
	--deny warnings \
	\
	--deny clippy::as_conversions \
	\
	--allow clippy::len_without_is_empty \
	--allow clippy::new_without_default \
	--allow clippy::single_match \
	--allow clippy::single_match_else \
	--allow clippy::type_complexity \
	--allow clippy::upper_case_acronyms \

(https://twitter.com/weihanglo/status/1661680417643143169 should help, eventually.)

Oh cool. That will be a nice feature.

[djc]

Right, I meant, I forget why we don't have those in the crate root as inner attributes like we do for other stuff.

[cpu]

Right, I meant, I forget why we don't have those in the crate root as inner attributes like we do for other stuff.

Ahhh, I understand. Some git spelunking suggests there used to be crate attributes for clippy config and they were lifted out into the helper in briansmith/webpki@2799332 as part of synchronizing with ring. I can't read between the lines to determine the rationale for that 🤔

@djc I could open a separate PR to move back to that approach if you think it's worthwhile. It would reduce some dev. friction 👍

[djc]

Yeah, I think that would be an improvement. I'd probably just get rid of the helper script.