Refactor test/ranges.jl range construction

[mkitti]

Refactor test/ranges.jl "range construction" testsets

Over several pull requests the inner @testset "range(;kw...)" in test/ranges.jl introduced in #38041 by @jw3126 to test the all keyword form of range was lost. Here we reintroduce it and add separate test sets for range(start, stop) and range(start, stop, length).

Let block and compact keyword syntax

The tests are also reformatted to use a let block rather than repeatedly calling first, last, step, and length. The let block also allows use to use the compact keyword calling syntax when the variable name matches the keyword name. Alignment is kept across the test sets.

Additional malformed calls of ranges

Additionally, several malformed calls of range are added based on other pull requests where such forms were proposed and found to be problematic or otherwise declined.

Summary

In summary, the refactor results in the following form with distinct tests groups for the range(; kw...), range(start, stop), and range(start, stop, length).

@testset "range construction" begin
    @testset "range(; kw...)" begin
        ...
        let start=first(r), stop=last(r), step=step(r), length=length(r)
            @test r === range(; start, stop, step        )
            @test r === range(; start, stop,       length)
            ...
        end
    end
    @testset "range(start, stop)" begin
        ...
        let start=first(r), stop=last(r), step=step(r), length=length(r)
            q = range(start, stop)
            ...
            @test q === range(  start;            length)
            ...
        end
    end
    @testset "range(start, stop, length)" begin
        ...
    end
end

History:

1. Extracted from range(; stop) and range(; length). Single keyword args only. Single pos arg not allowed. #39241 and related feature branches. This pull request only add tests and no new features.

[jw3126]

Should we add @test_broken q == range(; stop, length)? Not sure, equality seems very hard to achieve here.

[mkitti]

Actually on master I currently get equality:

julia> r = 2.8:20.0
2.8:1.0:19.8

julia> using Test

julia> let start=first(r), stop=last(r), step=step(r), length=length(r)
           q = range(start, stop)
           @test q == range(; stop, length)
       end
Test Passed

julia> versioninfo()
Julia Version 1.7.0-DEV.551
Commit 9daf90ab49* (2021-02-16 19:40 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-11.0.1 (ORCJIT, skylake)

[jw3126]

Thanks for this and all the energy you put into ranges. I have a package https://github.com/jw3126/RangeHelpers.jl where I experiment with ways to make range construction even more convenient. Would be interested in your opinion.

[mkitti]

I have a package https://github.com/jw3126/RangeHelpers.jl

This looks interesting. You should be able to extend Base.range for your Approach type rather than duplicating range in your package. I'll take a deeper look and comment over there.

[mkitti]

Rebased

[mkitti]

I'm abandoning this. I think some similar changes may have been merged already. I will close this shortly after reviewing if any changes should be resubmitted.