add output file to step.run

[mystic spade]

I have this tool invocation:

const lemon_run = b.addRunArtifact(lemon);
lemon_run.addArg("-q"); lemon_run.addFileArg(b.path("parser/parser.y"));

Lemon does not support overwriting the output file. it is hardcoded to be inputname with a differet suffix. how do i explain to the build system that this file will be created and use it later? I want something like addOutputFileArg but don't actually append an argument

[floral sierra]

if the file is gaurenteed to be outputted in a stable location based on the name, I dont see why you need to tell the build system about it
you can just use b.path(“parser/parser.whatever_the_new_suffix_is”)

although if lemon has an option that prints it to stdout instead of writing it to a file, you can use that along with lemon_run.captureStdOut()
that could be a good option

[mystic spade]

don't I have to declare the dependency between the tool running and the file being generated?

[mystic spade]

it doesnt :(

[floral sierra]

afaik the only time you need to declare dependencies is if editing that file would require rerunning that step

yeah addOutputFileArg doesnt seem to even set up a dependency or anything like that

[mystic spade]

well that is the case here. I want the buildsystem to rerun the tool if i change the parser.y file

[floral sierra]

that’s already done for you with the addFileArg(b.path(“parser/parse.y”)) line

it already depends on that path now

the output doesnt matter for that

[mystic spade]

i believe the returned lazypath has a reference to the output thing with has a reference to the step that it was created from. I dont know about build system internals but it seems possible to me that it uses this as a edge in the dependency DAG

[mystic spade]

are steps run even if they dont lead to the install step?

[floral sierra]

only if a step your user runs depends on them
the install step is the default step that runs when you do just zig build

[floral sierra]

I guess I cant say 100% for sure, but the make function of a step is the only place it manipulates GeneratedFiles and it doesnt seem to do anything with dependency logic
and just intuitively it wouldnt make sense to me
you can always try it out yourself

[mystic spade]

the problem i have with this is that I would like the tool to be run in some directory inside zig-cache and not pollute my sources

[mystic spade]

so then if the buildsystem does not see any path from the lemon run to the install step it wont run the tool and generate my parser then

    const lemon_run = b.addRunArtifact(lemon);
    lemon_run.addArg("-q");
    lemon_run.addFileArg(b.path("parser/parser.y"));
    lemon_run.addArg("#"); // trickery
    const parser_c = lemon_run.addOutputFileArg("parser.c");
    const parser_h = lemon_run.addOutputFileArg("parser.h");

I tried this btw it doesnt work lol

[floral sierra]

I guess you could have a writeFile step

with WriteFile.addCopyFile

[floral sierra]

that wont work since it’s not bash
it also wouldnt be able to automatically place the output into the cache dir for you
that’s up to the app
(the argument gets expanded into the cache dir so that’s what the app sees)

[mystic spade]

you mean copy the input file into the cache and run the tool there?

i'm not sure how exactly i can use b.addWriteFile to achieve this

[floral sierra]

you can do something like

const write_files_step = b.addWriteFiles();
write_files.addCopyFile(b.path(“parser/parser.c”), “parser.c”);
write_files.addCopyFile(b.path(“parser/parser.h”), “parser.h”);

and then write_files.getDirectory() will return the directory those files were put into

[mystic spade]

parser/parser.c? But I dont want build artifacts in my source directory. is there a way around this?

[floral sierra]

I guess you could delete those files after you copy them but idk how well supported that is in the build.zig

or you could copy the parser.y file into cache using this same strategy and then the parser.c and parser.h will be in that same directory in cache
I have no clue if that’s allowed though, im not sure that the build system expects anything but build steps to modify the cache directory

I dont see why it wouldnt work just feels a bit icky

another idea is that you can compile lemon from source and just patch it to allow adding a output file
which is annoying, sure, but you can PR it and itll be a lot more ergonomic and idiomatic

(you can compile it in the build.zig and use the package manager to fetch the source, so it shouldnt be too annoying)

hm
looks like you can use the -d parameter to specify the output directory

https://compiler-dept.github.io/lemon/

you can definitely use that

[mystic spade]

i was trying to create a directory and then express that there are files inside but failed

[floral sierra]

actually no, hm
Step.Run doesnt seem to have a way to add an output directory
seems like an oversight

[mystic spade]

i tried to do this but failed again to express the relationship between parser.y lazypath and parser.c that would be in the same directory but under a different name

[floral sierra]

yeah sorry, not sure how youd be able to do this