Diagnose missing target errors

[timbertson]

I've been converting a few of my own libraries to use jbuilder. It's gone fairly well so far, so thanks :) (and sorry for the influx of issues, I'll quiet down soon I promise ;))

But a number of times I've hit a wall when jbuilder says "nope", but I can't find a way to get more information about what it tried or why it couldn't do what I asked. Here's an example:

$ jbuilder build _build/default/examples/todomvc/main.bc.js
Don't know how to build _build/default/examples/todomvc/main.bc.js

Well.. there should be a build target there. In these sorts of cases I'd love some flags which enable logging about:

• what jbuild files it's loading
• what targets are defined in the given directory
• if I'm getting really desperate, what targets are defined in the entire workspace

In this case, the only troubleshooting I could do was:

• ls examples/todomvc/main.ml (yep, it's there)
• cat examples/todomvc/jbuild (yep, it defines an executable called "main")

At which point I'm pretty much out of ideas.

In the end, I figured out that I had created a bad jbuild-workspace - it was empty (which is documented as equivalent to (context default), but maybe that's not implemented in beta12?). I expect doing any sort of dump of "which targets are defined" would have more quickly pointed to a project-wide issue, as it would have been empty.

I eventually figured it out by trying other targets which had previously worked, and they could no longer be found. This process wasn't obvious either though, since top-level targets still seemed to kind of work (until I did a clean, then they became suspicious):

• jbuilder build vdoml.install - successfully built the install file, but didn't build any of the files it depends on
• jbuilder build @install - didn't appear to build anything (but didn't fail either)

[ghost]

Yh, the empty jbuild-workspace equivalent to (context default) is not released yet. Hopefully we should never end up with a system with 0 rules...

When you request a target that doesn't exist from the command line, jbuilder try to give a hint when it can (Did you mean ...?).

[ghost]

BTW, one thing that is close to what your are asking is jbuild rules.

[timbertson]

"Did you mean" is neat, but it's probably only going to work for typos - if it only gives you zero or one suggestion, it's not likely to be a good debugging aid, where you often want to scan the list of what's available to pick out patterns or surprises.

I tried jbuilder rules, but it wasn't happy:

$ jbuilder rules
Error: External library "utop" not found.
-> required by "src/.utop/jbuild (context default)"
Hint: try: jbuilder external-lib-deps --missing

I don't depend on utop anywhere, and I have a src/ directory but no src/.utop. I'm assuming it's a builtin thing?

$ jbuilder external-lib-deps --missing @install
# (no output)

$ jbuilder external-lib-deps --missing src/.utop/jbuild
Don't know how to build src/.utop/jbuild

[rgrinberg]

@timbertson utop is necessary for launching utop toplevels ($ jbuilder utop). Its absence shouldn't be breaking $ jbuilder utop though. That's an annoying deficiency.

[rgrinberg]

What I think might help here is a command to print targets. Would something like $ dune targets <dir> be useful for you @timbertson ?

[timbertson]

Yes, that sounds great for diagnosing this sort of problem.

…

On Sat., 22 Sep. 2018, 12:00 am Rudi Grinberg, ***@***.***> wrote: What I think might help here is a command to print targets. Would something like $ dune targets <dir> be useful for you @timbertson <https://github.com/timbertson> ? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#265 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAA3XB-nTj0_3-v1z-tvFBfLTZdNsSbDks5udPD_gaJpZM4PhfRh> .

[rgrinberg]

The team is pretty busy at the moment, so it's unlikely that we'll get to tackle this in the near/medium future. But if you'd like we can guide on how to implement this feature. It shouldn't be too difficult.

[timbertson]

I'm afriad I have my hands full too at the moment.