Source-based coverage

[vitorenesduarte]

With this PR, we start tracking coverage using LLVM's source-based coverage: https://blog.rust-lang.org/inside-rust/2020/11/12/source-based-code-coverage.html

• pin nightly version to avoid spurious errors (it's unlikely we need to bump this often, unless we need new compiler features)
• pin grcov version to avoid [ERROR] Execution count overflow detected. mozilla/grcov#555
• set LLVM_PROFILE_FILE="%m.profraw" to avoid overwrites of coverage data (which occur when several test binaries are run for the same crate): Output filenames for -Z instrument-coverage rust-lang/rust#79899
  • maybe the 30% coverage decreases (Fix clippy errors/warnings when upgrading to Rust 1.51 #839 (comment) and Research and implement tarpaulin instead of grcov #252 (comment)) are due to something like this

With this, coverage is at 67.7%, which seems to be an all-time high 😄

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Updated CHANGELOG.md

[codecov-io]

Codecov Report

Merging #840 (3f9563a) into master (4b0318c) will increase coverage by 38.5%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #840      +/-   ##
=========================================
+ Coverage    29.1%   67.7%   +38.5%     
=========================================
  Files         194     209      +15     
  Lines       10766   16812    +6046     
  Branches     4444       0    -4444     
=========================================
+ Hits         3134   11382    +8248     
- Misses       4653    5430     +777     
+ Partials     2979       0    -2979     

Impacted Files	Coverage Δ
light-client/src/macros.rs	14.7% <0.0%> (-25.3%)	⬇️
tendermint/src/config/node_key.rs	46.4% <0.0%> (-23.6%)	⬇️
tendermint/src/channel.rs	22.0% <0.0%> (-15.0%)	⬇️
light-client/src/types.rs	30.6% <0.0%> (-12.4%)	⬇️
tendermint/src/hash.rs	36.5% <0.0%> (-12.1%)	⬇️
tendermint/src/config/priv_validator_key.rs	39.1% <0.0%> (-10.9%)	⬇️
light-client/src/errors.rs	3.1% <0.0%> (-7.8%)	⬇️
testgen/src/jsonatr.rs	0.0% <0.0%> (ø)
light-node/src/error.rs	0.0% <0.0%> (ø)
light-node/src/config.rs	0.0% <0.0%> (ø)
... and 192 more

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[thanethomson]

Let's give this a try 👍 I'm looking forward to the results. Thanks @vitorenesduarte!

[romac]

Awesome, thanks a lot @vitorenesduarte !

[marco-c]

@vitorenesduarte could you try the latest version of grcov, with LLVM_PROFILE_FILE set to %p-%m.profraw instead of %m.profraw?

[vitorenesduarte]

@vitorenesduarte could you try the latest version of grcov, with LLVM_PROFILE_FILE set to %p-%m.profraw instead of %m.profraw?

@marco-c trying it here: #864