Improve object display

[xbwwj]

This Pull Request closes #4371.

It changes the following:

1. show constructor name when display object

   >> class Foo { a = 1 }
   undefined
   >> const foo = new Foo()
   undefined
   >> foo
   Foo {
      a: 1
   }
   
   // nested works well
   >> class Bar { b = new Foo() }
   undefined
   >> const bar = new Bar()
   undefined
   >> bar
   Bar {
      b: Foo {
          a: 1
       }  // <- indent error here, not brought by this PR
   }
   
   // work with `"Object"` as name
   >> class Object { a = 1 }
   undefined
   >> new Object()
   Object {
      a: 1
   }
   
   // plain does not show constructor name
   >> const plain = { a: 123 }
   undefined
   >> plain
   {
      a: 123
   }
   
   // builtin special classes need further improvement but not in this PR,
   // at least now we know its type
   >> new Float32Array([1,2,3,4,5])
   Float32Array {
   
   }

2. console.{log,error,...} now use JsValue::display for non string value

   >> console.log(123)
   123
   undefined
   >> console.log("456")
   456
   undefined
   >> console.log({a: 123, b: "456"})
   {
      a: 123,
      b: "456"
   }
   undefined

3. function and class display [class $name], [Function: $name]

   >> console.log(console.log)
   [Function: log]
   undefined
   >> class Foo {}
   undefined
   >> console.log(Foo)
   [class Foo]
   undefined
   >> console.log(ArrayBuffer)
   [class ArrayBuffer]  // <- FIXME: I'm not able to distinguish callable and constructor with current engine
   undefined               // as custom class `Foo` also satisfies `is_callable`

4. A flake.nix file that makes it easier for Nix users to setup environment and contribute to the project

[xbwwj]

@jedel1043 I think this PR is ready for review now.

[codecov]

Codecov Report

❌ Patch coverage is 40.32258% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.35%. Comparing base (6ddc2b4) to head (3de3fa4).
⚠️ Report is 502 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/value/display.rs	35.08%	37 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4377      +/-   ##
==========================================
+ Coverage   47.24%   50.35%   +3.11%     
==========================================
  Files         476      508      +32     
  Lines       46892    50906    +4014     
==========================================
+ Hits        22154    25635    +3481     
- Misses      24738    25271     +533     

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[xbwwj]

I'm not familiar with the codecov dashboard. How can I improve this score, by adding more unit tests?

[Razican]

I'm not familiar with the codecov dashboard. How can I improve this score, by adding more unit tests?

Codecov results show which lines of code are being run in the tests. It could be that some branches (if-else, match) are only being tested for one of the comparison results, instead of all, so they show in red.

Ideally, we should have specific tests for most of the branches. Either as separate tests or as more complete single tests.

[hansl]

We probably don't want the WASMI code in here. You should open a separate PR with it and remove it from here.

I cannot find do a review soon. I like this PR a lot. Thanks.

[xbwwj]

Sorry. I tried but still cannot get stated with codecov. There isn't even an entry of core/engine/value/display.rs in codecov link.

I also don't have access to codecov.io for my local code changes. Which local tool do you use, cargo-llvm-cov or tarpaulin? There is no related information in the documentation.

[hansl]

Sorry. You can follow the instructions at https://doc.rust-lang.org/beta/rustc/instrument-coverage.html

I personally use IntelliJ which has excellent coverage support. I know Rust Analyzer for VSCode does too.

Two notes;

1. let's remove all the Nix mentions and make a new PR with it. Focus PRs on single task/issue/feature.
2. You will need to run cargo fmt --all to fix the formatting.

[nekevss]

I wouldn't worry too much about the coverage either. It is definitely nice to have unit tests, but we typically don't reject PRs based off the codecov report.

[hansl]

This could be improved a bit; indentation issue, a lot of allocations, more tests. But I'll approve now and we can work on fixing it in the code base.

[hansl]

I really like the change, btw. Sorry I couldn't review faster, I was away.