Make --backend:cpp|js work for :test: code-blocks as well

[kaushalmodi]

Continues
9502e39

Ref:

• 9502e39#commitcomment-39087584
• nim doc --backend:js, nim doc --doccmd:-d:foo, nim r --backend:js, --doccmd:skip + other improvements #14278

Fixes #13129 .

/cc @Araq @timotheecour Can you please review this?

[Araq]

Well if I write nim c in the tests, I expect nim c. How about supporting nim $backend instead?

[kaushalmodi]

@Araq May be I wasn't clear.. it is hardcoded to nim c here:

Nim/lib/packages/docutils/rstgen.nim

Line 868 in 5ce30e0

params.testCmd = "nim c -r $1"

[kaushalmodi]

If you intend to use the c backend for those tests, this PR won't change anything.

[Araq]

It's hardcoded, yes, but I think if I write it down myself your code will be applied anyhow.

[kaushalmodi]

I think if I write it down myself your code will be applied anyhow

Hmm, yes. But are there real use cases where in the same .nim file, you have a mix of nim c .. and nim cpp .. :test: code blocks?

[kaushalmodi]

I'll close this PR. I will update my std_vector wrapper with:

.. code-block:: nim
    :test: "nim cpp -r $1"