use runtime-wasm feature instead of assuming no_std to be wasm

[brenzi]

fixes #5547

Main steps done:

1. replace #[cfg(feature = "std")] by #[cfg(not(feature = "runtime-wasm"))] and the logical opposite

find . -type f -name "*.rs" ! -path "./target/*" -print0 | xargs -0 sed -i 's/#\[cfg(feature = "std")\]/#\[cfg(not(feature = "runtime-wasm"))\]/g' 
find . -type f -name "*.rs" ! -path "./target/*" -print0 | xargs -0 sed -i 's/#\[cfg(not(feature = "std"))\]/#\[cfg(feature = "runtime-wasm")\]/g' 

2. introduce runtime-wasm feature in all tomls (probably that's too many as not all are needed for runtime)

find . -type f -name "*.toml" -print0 | xargs -0 sed -i 's/default = \[ "std" \]/default = \[ "std" \]\nruntime-wasm = \[\]/g' 
find . -type f -name "*.toml" -print0 | xargs -0 sed -i 's/default = \["std"\]/default = \[ "std" \]\nruntime-wasm = \[\]/g' 

3. let wasm-builder-runner add the runtime-wasm feature to rustc args
4. manual fixes, i.e. to gate RuntimeDebug derivation

this is WIP. not yet sure if the approach makes sense

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[bkchr]

In general the runtime-wasm feature should only be used where it is required!

This means mostly primitives-io, because most other crates are still using the no_std "legally" by making themselves compilable for no-std.

Everywhere where we have special code that assumes no_std == runtime-wasm, we would need to switch it to runtime-wasm.

[bkchr]

Why?

[brenzi]

from the errors I concluded that the feature runtime-wasm isn't applied automatically by the build script. Is that wrong?

[bkchr]

When the feature is present in the cargo.toml, the wasm-builder should activate it automatically.

[bkchr]

?

[brenzi]

I just tried to reset and try bottom up starting with sp-io only. However, the errors explode and I think it takes someone with deep knowledge of the code to distinguish between no_std == wasm assumptions and legit std switches.

Try and err will lead us nowhere because iterations are long as everything is rebuilt upon changes to fundamental crates.

[brenzi]

I would assume we need to touch at least these:

• sp-io
• sp-core
• sp-debug-derive
• runtime-interface

TBC

[bkchr]

I just tried to reset and try bottom up starting with sp-io only. However, the errors explode and I think it takes someone with deep knowledge of the code to distinguish between no_std == wasm assumptions and legit std switches.

Try and err will lead us nowhere because iterations are long as everything is rebuilt upon changes to fundamental crates.

I assume you desperately waiting for this feature? 🙈

[brenzi]

well, it would make our lives a lot easier for sure 🙏

[brenzi]

well, I tried a little harder, but giving up for today....

[athei]

Does this kind of "negative feature" even work with Cargo.toml? How do you express that you want to enable the std feature of some (non parity) dependency when runtime-wasm is not set?

[gnunicorn]

Closing for a lack of progress.