WIP

crates/spk-solve/crates/graph/src/error.rs

@@ -102,11 +102,24 @@ impl FormatError for Error {
         let mut msg = String::new();
         msg.push_str("Failed to resolve");
         match self {
-            Error::FailedToResolve(_graph) => {
+            Error::FailedToResolve(graph) => {
                 // TODO: provide a summary based on the graph
                 msg.push_str(
                     ": there is no solution for these requests using the available packages",
                 );
+                msg.push_str("\n * TODO: provide a summary based on the graph");
+                let root = graph.root.read().await;
+                for d in root.output_decisions() {
+                    msg.push_str("\n * D");
+                    for c in &d.changes {
+                        msg.push_str("\n C: ");
+                        msg.push_str(format!("{c:?}").as_str());
+                    }
+                    for n in &d.notes {
+                        msg.push_str("\n N: ");
+                        msg.push_str(format!("{n:?}").as_str());
+                    }
+                }
             }
             Error::SolverError(reason) => {
                 msg.push_str("\n * ");

crates/spk-solve/crates/graph/src/graph.rs

@@ -746,6 +746,10 @@ impl Node {
             )),
         );
     }
+
+    pub fn output_decisions(&self) -> impl Iterator<Item = &Arc<Decision>> {
+        self.outputs_decisions.iter()
+    }
 }
 
 /// Some additional information left by the solver

crates/spk-solve/src/solver_test.rs

@@ -7,6 +7,7 @@ use std::sync::Arc;
 use rstest::{fixture, rstest};
 use spfs::encoding::EMPTY_DIGEST;
 use spk_schema::foundation::fixtures::*;
+use spk_schema::foundation::format::FormatError;
 use spk_schema::foundation::ident_component::Component;
 use spk_schema::foundation::opt_name;
 use spk_schema::ident::{
@@ -2541,3 +2542,30 @@ async fn test_version_number_masking(
     );
     assert_ne!(resolved.spec.ident().build(), &Build::Source);
 }
+
+#[rstest]
+#[tokio::test]
+async fn test_solver_error_messages(mut solver: Solver) {
+    let options = option_map! {};
+    let repo = make_repo!(
+        [
+            {"pkg": "pkg-a/0.9.0"},
+            {"pkg": "pkg-a/1.0.0"},
+            {"pkg": "pkg-a/1.2.0"},
+            {"pkg": "pkg-a/1.2.1"},
+            {"pkg": "pkg-a/2.0.0"},
+            {"pkg": "pkg-b/1.0.0", "install": {"requirements": [{"pkg": "pkg-a/>2.0"}]}},
+        ]
+    );
+
+    solver.update_options(options);
+    solver.add_repository(Arc::new(repo));
+    solver.add_request(request!("pkg-b/1.0"));
+
+    let err = run_and_print_resolve_for_tests(&solver)
+        .await
+        .expect_err("Expected solve to fail");
+    let msg = err.format_error(u8::MAX).await;
+    eprintln!("\n--->\n{msg}\n<---\n");
+    assert_eq!(msg, "fudge");
+}