Collapse unavailable packages in resolver errors (#6154)

Uses my expanding tree reduction knowledge from #6092 to improve the
long-standing issue of verbose messages for unavailable packages.

Implements https://github.com/pubgrub-rs/pubgrub/issues/232, but
post-resolution instead of during resolution.

Partially addresses https://github.com/astral-sh/uv/issues/5046
Closes https://github.com/astral-sh/uv/issues/2519

crates/uv-resolver/src/error.rs

@@ -222,6 +222,13 @@ impl std::fmt::Display for NoSolutionError {
 
         // Transform the error tree for reporting
         let mut tree = self.error.clone();
+        let should_display_tree = std::env::var_os("UV_INTERNAL__SHOW_DERIVATION_TREE").is_some()
+            || tracing::enabled!(tracing::Level::TRACE);
+
+        if should_display_tree {
+            display_tree(&tree, "Resolver derivation tree before reduction");
+        }
+
         collapse_no_versions_of_workspace_members(&mut tree, &self.workspace_members);
 
         if self.workspace_members.len() == 1 {
@@ -229,11 +236,10 @@ impl std::fmt::Display for NoSolutionError {
             drop_root_dependency_on_project(&mut tree, project);
         }
 
-        // Display the tree if enabled
+        collapse_unavailable_versions(&mut tree);
-        if std::env::var_os("UV_INTERNAL__SHOW_DERIVATION_TREE").is_some()
+
-            || tracing::enabled!(tracing::Level::TRACE)
+        if should_display_tree {
-        {
+            display_tree(&tree, "Resolver derivation tree after reduction");
-            display_tree(&tree);
         }
 
         let report = DefaultStringReporter::report_with_formatter(&tree, &formatter);
@@ -257,15 +263,18 @@ impl std::fmt::Display for NoSolutionError {
 }
 
 #[allow(clippy::print_stderr)]
-fn display_tree(error: &DerivationTree<PubGrubPackage, Range<Version>, UnavailableReason>) {
+fn display_tree(
+    error: &DerivationTree<PubGrubPackage, Range<Version>, UnavailableReason>,
+    name: &str,
+) {
     let mut lines = Vec::new();
     display_tree_inner(error, &mut lines, 0);
     lines.reverse();
 
     if std::env::var_os("UV_INTERNAL__SHOW_DERIVATION_TREE").is_some() {
-        eprintln!("Resolver error derivation tree\n{}", lines.join("\n"));
+        eprintln!("{name}\n{}", lines.join("\n"));
     } else {
-        trace!("Resolver error derivation tree\n{}", lines.join("\n"));
+        trace!("{name}\n{}", lines.join("\n"));
     }
 }
 
@@ -355,6 +364,105 @@ fn collapse_no_versions_of_workspace_members(
     }
 }
 
+/// Given a [`DerivationTree`], collapse incompatibilities for versions of a package that are
+/// unavailable for the same reason to avoid repeating the same message for every unavailable
+/// version.
+fn collapse_unavailable_versions(
+    tree: &mut DerivationTree<PubGrubPackage, Range<Version>, UnavailableReason>,
+) {
+    match tree {
+        DerivationTree::External(_) => {}
+        DerivationTree::Derived(derived) => {
+            match (
+                Arc::make_mut(&mut derived.cause1),
+                Arc::make_mut(&mut derived.cause2),
+            ) {
+                // If we have a node for unavailable package versions
+                (
+                    DerivationTree::External(External::Custom(package, versions, reason)),
+                    ref mut other,
+                )
+                | (
+                    ref mut other,
+                    DerivationTree::External(External::Custom(package, versions, reason)),
+                ) => {
+                    // First, recursively collapse the other side of the tree
+                    collapse_unavailable_versions(other);
+
+                    // If it's not a derived tree, nothing to do.
+                    let DerivationTree::Derived(Derived {
+                        terms,
+                        shared_id,
+                        cause1,
+                        cause2,
+                    }) = other
+                    else {
+                        return;
+                    };
+
+                    // If the other tree has an unavailable package...
+                    match (&**cause1, &**cause2) {
+                        // Note the following cases are the same, but we need two matches to retain
+                        // the ordering of the causes
+                        (
+                            _,
+                            DerivationTree::External(External::Custom(
+                                other_package,
+                                other_versions,
+                                other_reason,
+                            )),
+                        ) => {
+                            // And the package and reason are the same...
+                            if package == other_package && reason == other_reason {
+                                // Collapse both into a new node, with a union of their ranges
+                                *tree = DerivationTree::Derived(Derived {
+                                    terms: terms.clone(),
+                                    shared_id: *shared_id,
+                                    cause1: cause1.clone(),
+                                    cause2: Arc::new(DerivationTree::External(External::Custom(
+                                        package.clone(),
+                                        versions.union(other_versions),
+                                        reason.clone(),
+                                    ))),
+                                });
+                            }
+                        }
+                        (
+                            DerivationTree::External(External::Custom(
+                                other_package,
+                                other_versions,
+                                other_reason,
+                            )),
+                            _,
+                        ) => {
+                            // And the package and reason are the same...
+                            if package == other_package && reason == other_reason {
+                                // Collapse both into a new node, with a union of their ranges
+                                *tree = DerivationTree::Derived(Derived {
+                                    terms: terms.clone(),
+                                    shared_id: *shared_id,
+                                    cause1: Arc::new(DerivationTree::External(External::Custom(
+                                        package.clone(),
+                                        versions.union(other_versions),
+                                        reason.clone(),
+                                    ))),
+                                    cause2: cause2.clone(),
+                                });
+                            }
+                        }
+                        _ => {}
+                    }
+                }
+                // If not, just recurse
+                _ => {
+                    collapse_unavailable_versions(Arc::make_mut(&mut derived.cause1));
+                    collapse_unavailable_versions(Arc::make_mut(&mut derived.cause2));
+                }
+            }
+        }
+    }
+}
+
 /// Given a [`DerivationTree`], drop dependency incompatibilities from the root
 /// to the project.
 ///

crates/uv/tests/cache_prune.rs

@@ -241,10 +241,15 @@ fn prune_unzipped() -> Result<()> {
       ╰─▶ Because only the following versions of iniconfig are available:
               iniconfig<=0.1
               iniconfig>=1.0.0
-          and iniconfig==0.1 network connectivity is disabled, but the metadata wasn't found in the cache, we can conclude that iniconfig<1.0.0 cannot be used.
+          and any of:
-          And because iniconfig==1.0.0 network connectivity is disabled, but the metadata wasn't found in the cache and iniconfig==1.0.1 network connectivity is disabled, but the metadata wasn't found in the cache, we can conclude that iniconfig<1.1.0 cannot be used.
+              iniconfig==0.1
-          And because iniconfig==1.1.0 network connectivity is disabled, but the metadata wasn't found in the cache and iniconfig==1.1.1 network connectivity is disabled, but the metadata wasn't found in the cache, we can conclude that iniconfig<2.0.0 cannot be used.
+              iniconfig==1.0.0
-          And because iniconfig==2.0.0 network connectivity is disabled, but the metadata wasn't found in the cache and you require iniconfig, we can conclude that your requirements are unsatisfiable.
+              iniconfig==1.0.1
+              iniconfig==1.1.0
+              iniconfig==1.1.1
+              iniconfig==2.0.0
+          network connectivity is disabled, but the metadata wasn't found in the cache, we can conclude that iniconfig<1.0.0 cannot be used.
+          And because you require iniconfig, we can conclude that your requirements are unsatisfiable.
 
           hint: Pre-releases are available for iniconfig in the requested range (e.g., 0.2.dev0), but pre-releases weren't enabled (try: `--prerelease=allow`)
 

crates/uv/tests/pip_install.rs

@@ -1925,95 +1925,51 @@ fn install_only_binary_all_and_no_binary_all() {
               anyio>=3.0.0,<=3.6.2
               anyio>=3.7.0,<=3.7.1
               anyio>=4.0.0
-          and anyio==1.0.0 has no usable wheels and building from source is disabled, we can conclude that any of:
+          and any of:
+              anyio==1.0.0
+              anyio==1.1.0
+              anyio==1.2.0
+              anyio==1.2.1
+              anyio==1.2.2
+              anyio==1.2.3
+              anyio==1.3.0
+              anyio==1.3.1
+              anyio==1.4.0
+              anyio==2.0.0
+              anyio==2.0.1
+              anyio==2.0.2
+              anyio==2.1.0
+              anyio==2.2.0
+              anyio==3.0.0
+              anyio==3.0.1
+              anyio==3.1.0
+              anyio==3.2.0
+              anyio==3.2.1
+              anyio==3.3.0
+              anyio==3.3.1
+              anyio==3.3.2
+              anyio==3.3.3
+              anyio==3.3.4
+              anyio==3.4.0
+              anyio==3.5.0
+              anyio==3.6.0
+              anyio==3.6.1
+              anyio==3.6.2
+              anyio==3.7.0
+              anyio==3.7.1
+              anyio==4.0.0
+              anyio==4.1.0
+              anyio==4.2.0
+              anyio==4.3.0
+              anyio==4.4.0
+          has no usable wheels and building from source is disabled, we can conclude that any of:
               anyio<1.1.0
               anyio>1.4.0,<2.0.0
               anyio>2.2.0,<3.0.0
               anyio>3.6.2,<3.7.0
               anyio>3.7.1,<4.0.0
            cannot be used.
-          And because anyio==1.1.0 has no usable wheels and building from source is disabled and anyio==1.2.0 has no usable wheels and building from source is disabled, we can conclude that any of:
+          And because you require anyio, we can conclude that your requirements are unsatisfiable.
-              anyio<1.2.1
-              anyio>1.4.0,<2.0.0
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==1.2.1 has no usable wheels and building from source is disabled and anyio==1.2.2 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<1.2.3
-              anyio>1.4.0,<2.0.0
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==1.2.3 has no usable wheels and building from source is disabled and anyio==1.3.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<1.3.1
-              anyio>1.4.0,<2.0.0
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==1.3.1 has no usable wheels and building from source is disabled and anyio==1.4.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<2.0.0
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==2.0.0 has no usable wheels and building from source is disabled and anyio==2.0.1 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<2.0.2
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==2.0.2 has no usable wheels and building from source is disabled and anyio==2.1.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<2.2.0
-              anyio>2.2.0,<3.0.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==2.2.0 has no usable wheels and building from source is disabled and anyio==3.0.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.0.1
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.0.1 has no usable wheels and building from source is disabled and anyio==3.1.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.2.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.2.0 has no usable wheels and building from source is disabled and anyio==3.2.1 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.3.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.3.0 has no usable wheels and building from source is disabled and anyio==3.3.1 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.3.2
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.3.2 has no usable wheels and building from source is disabled and anyio==3.3.3 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.3.4
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.3.4 has no usable wheels and building from source is disabled and anyio==3.4.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.5.0
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.5.0 has no usable wheels and building from source is disabled and anyio==3.6.0 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.6.1
-              anyio>3.6.2,<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.6.1 has no usable wheels and building from source is disabled and anyio==3.6.2 has no usable wheels and building from source is disabled, we can conclude that any of:
-              anyio<3.7.0
-              anyio>3.7.1,<4.0.0
-           cannot be used.
-          And because anyio==3.7.0 has no usable wheels and building from source is disabled and anyio==3.7.1 has no usable wheels and building from source is disabled, we can conclude that anyio<4.0.0 cannot be used.
-          And because anyio==4.0.0 has no usable wheels and building from source is disabled and anyio==4.1.0 has no usable wheels and building from source is disabled, we can conclude that anyio<4.2.0 cannot be used.
-          And because anyio==4.2.0 has no usable wheels and building from source is disabled and anyio==4.3.0 has no usable wheels and building from source is disabled, we can conclude that anyio<4.4.0 cannot be used.
-          And because anyio==4.4.0 has no usable wheels and building from source is disabled and you require anyio, we can conclude that your requirements are unsatisfiable.
 
           hint: Pre-releases are available for anyio in the requested range (e.g., 4.0.0rc1), but pre-releases weren't enabled (try: `--prerelease=allow`)
     "###