Avoid subsequent index hint when no versions are available on the first index (#9332)

As reported in #9331, this hint is
misleading.

---------

Co-authored-by: Charlie Marsh <[email protected]>

Author: zanieb

crates/uv-resolver/src/pubgrub/report.rs

@@ -895,21 +895,29 @@ impl PubGrubReportFormatter<'_> {
         // Add hints due to the package being available on an index, but not at the correct version,
         // with subsequent indexes that were _not_ queried.
         if matches!(selector.index_strategy(), IndexStrategy::FirstIndex) {
-            if let Some(found_index) = available_indexes.get(name).and_then(BTreeSet::first) {
-                // Determine whether the index is the last-available index. If not, then some
-                // indexes were not queried, and could contain a compatible version.
-                if let Some(next_index) = index_locations
-                    .indexes()
-                    .map(Index::url)
-                    .skip_while(|url| *url != found_index)
-                    .nth(1)
-                {
-                    hints.insert(PubGrubHint::UncheckedIndex {
-                        name: name.clone(),
-                        range: set.clone(),
-                        found_index: found_index.clone(),
-                        next_index: next_index.clone(),
-                    });
+            // Do not include the hint if the set is "all versions". This is an unusual but valid
+            // case in which a package returns a 200 response, but without any versions or
+            // distributions for the package.
+            if !set
+                .iter()
+                .all(|range| matches!(range, (Bound::Unbounded, Bound::Unbounded)))
+            {
+                if let Some(found_index) = available_indexes.get(name).and_then(BTreeSet::first) {
+                    // Determine whether the index is the last-available index. If not, then some
+                    // indexes were not queried, and could contain a compatible version.
+                    if let Some(next_index) = index_locations
+                        .indexes()
+                        .map(Index::url)
+                        .skip_while(|url| *url != found_index)
+                        .nth(1)
+                    {
+                        hints.insert(PubGrubHint::UncheckedIndex {
+                            name: name.clone(),
+                            range: set.clone(),
+                            found_index: found_index.clone(),
+                            next_index: next_index.clone(),
+                        });
+                    }
                 }
             }
         }

crates/uv/tests/it/pip_compile.rs

@@ -12439,6 +12439,37 @@ fn compile_index_url_first_match_marker() -> Result<()> {
     Ok(())
 }
 
+/// Install a package via `--extra-index-url`.
+///
+/// If the package "exists" on the "extra" index, but without any versions, the resolution
+/// should fail by default (even though a compatible version exists on the "primary" index).
+#[test]
+fn compile_index_url_first_match_all_versions() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("pandas")?;
+
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("--index-url")
+        .arg("https://pypi.org/simple")
+        .arg("--extra-index-url")
+        .arg("https://test.pypi.org/simple")
+        .arg("requirements.in")
+        .arg("--no-deps"), @r###"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+      × No solution found when resolving dependencies:
+      ╰─▶ Because there are no versions of pandas and you require pandas, we can conclude that your requirements are unsatisfiable.
+    "###
+    );
+
+    Ok(())
+}
+
 /// Install a package via `--extra-index-url`.
 ///
 /// If the package exists exist on the "extra" index, but at an incompatible version, the