No way to get logs for `highs::Model::try_new`

[taktoa]

Sometimes, when you call highs::Model::new, you get this vexing informationless output:

HiGHS error: invalid problem: Error

The only way around this is to patch the highs crate:

diff --git a/src/lib.rs b/src/lib.rs
index 3176008..a876b94 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -290,7 +290,7 @@ impl Model {
     /// Returns an error if the problem is incoherent
     pub fn try_new<P: Into<Problem<ColMatrix>>>(problem: P) -> Result<Self, HighsStatus> {
         let mut highs = HighsPtr::default();
-        highs.make_quiet();
+        // highs.make_quiet();
         let problem = problem.into();
         log::debug!(
             "Adding a problem with {} variables and {} constraints to HiGHS",

Can this be made configurable?

[lovasoa]

Yes, this would be nice ! PR welcome ! We need to better integrate with Highs error handling

[taktoa]

I'm happy to contribute, but there are some decisions to make.

• The simplest option would be to just delete the make_quiet line as in my diff, and then users can add it back as desired. However, this could be annoying for users. It seems like there are about 3 direct dependents of highs and then another 15 or so that depend on good_lp. So maybe it's not a big deal as long as good_lp adds a make_quiet call?
• Another option is to move the make_quiet call to new, which probably has a smaller blast radius.
• Another option is to add a new method try_new_loud (or something). Zero blast radius, but maybe a bit ugly.

Any thoughts on how to proceed?

[lovasoa]

I think the last one is the best. I think libraries shouldn't touch stdout/stderr unless explicitly asked.

[lovasoa]

Additionally, if there are other ways to get error information from highs, we should use them, in order to still be able to surface useful context in our own error objects.

[KnorpelSenf]

I think the last one is the best. I think libraries shouldn't touch stdout/stderr unless explicitly asked.

I fully agree with this

[taktoa]

I realize now that I had a slight misunderstanding of what make_quiet is doing. I had assumed that the highs crate would register callbacks so that highs logging is sent through the log Rust API, but I guess it is actually just being sent to stdout/err. #34 seems related to fixing that.