compiler: Introduce non-nilable read_file macro

[woodruffw]

Follow-up on #6967.

The original (nilable) macro has been renamed to read_file?.

[Sija]

e -> ex plz

[yxhuvud]

Also, one question is if it is a good idea to rescue all possible errors instead of only the specific one that is raised if the file doesn't exist.

[Sija]

@yxhuvud I don't see a problem with it since they're re-raised and the only meaningful call (which might raise) is File.read.

[woodruffw]

and the only meaningful call (which might raise) is File.read

Yep, this was my reasoning here 🙂

[RX14]

read_file should return nil. From my experience, all other macro methods return nil instead of raising in the "missing" case. Since the macro language is dynamically typed, returning nil instead of erroring is the better default.

I vote close this PR. the || raise is the correct way to do this in macro-world.

[woodruffw]

all other macro methods return nil instead of raising in the "missing" case

Two counterexamples: Both the system and run macros raise on their error cases (failed execution and missing file, respectively). I'd argue that read_file bears more resemblance in kind to these two macros than others, and so should raise like them.

Similarly, from the end user's perspective, I'd argue that raising an error is a better default: returning a nil literal converts an I/O failure into a type mismatch, or (worse!) silently does the wrong thing if the user only ever calls #to_s or any other quack-y calls. That's avoidable with the || raise workaround, but I think doing it by default is more programmer-friendly.

[ysbaddaden]

@RX14 the run macro raises if the executed program exits with a non zero status.

If I embed a file, I expect the file to exist and be readable. I want a compile time error with the actual reason if it failed to. I don't want to deal with a nilable or have to raise myself a redundant read_file("path/to/file.png") || raise "failed to embed path/to/file.png" when the macro just could do it and give me the actual reason.

[RX14]

Oh, I thought system didn't raise. I guess this is fine then.