Allow globally suppressing compiler warnings

[heaths]

When adding NuGet packages with common dependency but with different versions in a Jupyter notebook, compiler warning CS1701 occurs. To suppress this, each code cell needs #pragma warning disable CS1701. This becomes distracting when using a notebook as an interactive tutorial, so it would be great if suppression could be done globally - perhaps even a Directory.Build.props file in a parent or ancestor directory (like MSBuild project files). Or, at the very least, if a single #pragma would disable a warning for all cells.

An example of the error without the #pragma would be using the following in a code cell:

#r "nuget:Azure.Identity"
#r "nuget:Azure.Security.KeyVault.Secrets"

(8,27): warning CS1701: Assuming assembly reference 'Azure.Core, Version=1.0.2.0, Culture=neutral, PublicKeyToken=92742159e12e44c8' used by 'Azure.Security.KeyVault.Secrets' matches identity 'Azure.Core, Version=1.4.1.0, Culture=neutral, PublicKeyToken=92742159e12e44c8' of 'Azure.Core', you may need to supply runtime policy

[heaths]

Here's an example of where I have to add #pragmas to suppress these, and on one of the executable blocks it doesn't even work (see toward the bottom where the warning is still emitted): https://github.com/heaths/azure-sdk-notebooks/blob/886ca19ead4c3de9a921e47ee03c0c84bcfa3d68/dotnet/Secrets%20in%20Key%20Vault.ipynb

[ArrowRaider]

I have a block that is emitting 3 of these warnings, and the pragma statement only removes 1 of them, leaving the other 2 present.

[jonsequitur]

We would probably implement a fix for this related to #890. The general goal there is to make sure that we use existing, familiar implementations as much as possible.

One theory as to why the #pragma doesn't seem to stick is that each submission (e.g. cell) is actually compiled into a different assembly. Any thoughts on this, @tmat?

[tmat]

RE CS1701: This warning is obsolete and shouldn't be reported at all. The script engine can suppress these warnings globally.
RE #pragma - yes, these are scoped per compilation unit, i.e. submission. The host can define host-level command to suppress warnings globally.

[MSDNAndi]

Any news on this? This is super actionable as especially in the AI craze, there are a lot of prerelease packages from Microsoft, OpenAI and others, and every cell that uses anything from those packages currently needs to have the pragma warning disable.

[jonsequitur]

One approach that could work would be a magic command (e.g. something like #!suppress-warnings CS1701) that suppresses a warning for current and future submissions. This would probably be fairly simple to add even for a first-time contributor to the project.