Add Branch and Function coverage to lcov output. about coverage

[srawlins]

Big +1

[JZ-at-TP]

+1 from 2019

[liamappelbe]

Update: Function coverage is implemented, and I'm working on branch coverage at the moment.

[felangel]

+1 from 2020

[micaelcid]

+1 from 2021

[liamappelbe]

Update: I have an implementation of branch coverage sitting in a PR, but branch coverage required some VM work and a new service API, so the PR is blocked on the service API updating to v8.2.0. Eta is a few weeks.

[nirwannursabda]

any update for Function coverage?
we already in the end of 2019 :)

[cmc5788]

It sounds like there's two separate requests here, both involving coarsening the coverage data to make it easier to read. I looked into the feasibility of supporting this in the VM (not for the web).

1. Function level. This is easy enough, because the VM service API can already give us code ranges for every function. We can coarsen the coverage data using these ranges. I will start work on this soon.
2. Branch/block level. This is much harder. There's no way of getting code ranges for blocks ATM. We could potentially add a new RPC to the API, but this would be quite a lot of work.

How important is the branch/block level info? Would function level info be sufficient for your needs?

My personal feeling is that with line level on one end and function level on the other, it would cover a good span.

branch would certainly be nice to have in the long-run, but the effort to value ratio seems like it would favor getting function coverage sooner.

[a-siva]

bumping priority as it appears to be an issue for customers

[IchordeDionysos]

I would prefer branch coverage as it gives you way more information/metadata on what is actually covered than line and especially function coverage can give you!

I am really not sure what useful metric function coverage would give you?!

With Branch coverage, you can make informed decisions on how much of your if/else, switch/case, ... statements are covered and make sure that nobody accidentally missed an else statement, as it would be reflected in your coverage report that this else was not covered!

[Eghosa-Osayande]

+1 from 2022

[depimomo]

+1 from 2022

[acoutts]

Would love to see this implemented as well! Looks like still there is no function coverage.

[a-siva]

/cc @liamappelbe

[liamappelbe]

It sounds like there's two separate requests here, both involving coarsening the coverage data to make it easier to read. I looked into the feasibility of supporting this in the VM (not for the web).

1. Function level. This is easy enough, because the VM service API can already give us code ranges for every function. We can coarsen the coverage data using these ranges. I will start work on this soon.
2. Branch/block level. This is much harder. There's no way of getting code ranges for blocks ATM. We could potentially add a new RPC to the API, but this would be quite a lot of work.

How important is the branch/block level info? Would function level info be sufficient for your needs?

[cmc5788]

To follow up a bit on my comment from last March;

branch would certainly be nice to have in the long-run, but the effort to value ratio seems like it would favor getting function coverage sooner.

My definition of "long-run" has changed a bit since due to the passage of time and more experience with the limitations of line coverage. I 100% agree with @IchordeDionysos :

With Branch coverage, you can make informed decisions on how much of your if/else, switch/case, ... statements are covered and make sure that nobody accidentally missed an else statement, as it would be reflected in your coverage report that this else was not covered!

[amarghosh]

Is this available in Flutter? I ran flutter test --coverage, but genhtml still complains about missing function and branch data. I am using flutter 2.8.1

[liamappelbe]

@amarghosh Flutter has their own coverage implementation, so it would need to be implemented there independently. I help out with their coverage implementation, but I'm not on the flutter team, so I don't know if they want the feature or not. File a bug with them, and if they think it's a good idea I'll help add it.

[liamappelbe]

Filed flutter/flutter#108313