add a "check only" compiler flag to get compiler errors without emitting build artifacts

[kevinw]

Having the compiler check your code for errors without emitting code would be very useful for IDEs and text editors with IDE-like plugins.

Something like:

zig check src/main.zig

Another possibility could be that you have to add a "check" task to your build.zig, but you set some kind of "null" target.

[andrewrk]

Thanks for filing the issue for this.

It needs to be a flag to one of the other build commands, and there does have to be a target. Consider this code:

if (builtin.os == .windows and otherCondition()) {
    @compileError("something went wrong");
}

Zig also needs to know whether e.g. pub fn main() is an entry point or not based on build
exe, build-obj, build-lib. So those still need to be the command names.

So this will look like an additional flag, for example --check-only. (If anyone knows the names of the equivalent flags from, e.g. clang or java please let me know so we can match that standard name)

Related issue: #3028

[iguessthislldo]

(If anyone knows the names of the equivalent flags from, e.g. clang or java please let me know so we can match that standard name)

The clang and GCC option for this is -fsyntax-only. I copied this term in a work project project as --syntax-only.

[zimmi]

The Java compiler (javac) doesn't support this feature. Running the JVM via java supports --dry-run.

[daurnimator]

--dry-run is a common flag for this across various tools

[andrewrk]

This is now supported with -fno-emit-bin.