Stable sorting of requirements.txt in universal mode (#5334)

The `RequirementsTxtComparator` was written assuming there is one
distribution per package name. This changed with the universal
resolution, which allows multiple versions or urls for the same package
name. The sorting we emitted for these new entries was incidental.

With this change, we properly sort these entries by name, version and
then url in universal mode.

This is an output format change for `--universal` users.

crates/uv-resolver/src/resolution/graph.rs

@@ -241,6 +241,7 @@ impl ResolutionGraph {
                 // Add the distribution to the graph.
                 let index = petgraph.add_node(ResolutionGraphNode::Dist(AnnotatedDist {
                     dist,
+                    version: version.clone(),
                     extra: extra.clone(),
                     dev: dev.clone(),
                     hashes,

crates/uv-resolver/src/resolution/mod.rs

@@ -1,6 +1,7 @@
 use std::fmt::Display;
 
 use distribution_types::{DistributionMetadata, Name, ResolvedDist, VersionOrUrlRef};
+use pep440_rs::Version;
 use pypi_types::HashDigest;
 use uv_distribution::Metadata;
 use uv_normalize::{ExtraName, GroupName, PackageName};
@@ -20,6 +21,7 @@ mod requirements_txt;
 #[derive(Debug, Clone)]
 pub(crate) struct AnnotatedDist {
     pub(crate) dist: ResolvedDist,
+    pub(crate) version: Version,
     pub(crate) extra: Option<ExtraName>,
     pub(crate) dev: Option<GroupName>,
     pub(crate) hashes: Vec<HashDigest>,

crates/uv-resolver/src/resolution/requirements_txt.rs

@@ -5,6 +5,7 @@ use std::path::Path;
 use itertools::Itertools;
 
 use distribution_types::{DistributionMetadata, Name, ResolvedDist, Verbatim, VersionOrUrlRef};
+use pep440_rs::Version;
 use pep508_rs::{split_scheme, MarkerTree, Scheme};
 use pypi_types::HashDigest;
 use uv_normalize::{ExtraName, PackageName};
@@ -15,6 +16,7 @@ use crate::resolution::AnnotatedDist;
 /// A pinned package with its resolved distribution and all the extras that were pinned for it.
 pub(crate) struct RequirementsTxtDist {
     pub(crate) dist: ResolvedDist,
+    pub(crate) version: Version,
     pub(crate) extras: Vec<ExtraName>,
     pub(crate) hashes: Vec<HashDigest>,
     pub(crate) markers: Option<MarkerTree>,
@@ -133,14 +135,27 @@ impl RequirementsTxtDist {
             }
         }
 
-        RequirementsTxtComparator::Name(self.name())
+        if let VersionOrUrlRef::Url(url) = self.version_or_url() {
+            RequirementsTxtComparator::Name {
+                name: self.name(),
+                version: &self.version,
+                url: Some(url.verbatim()),
+            }
+        } else {
+            RequirementsTxtComparator::Name {
+                name: self.name(),
+                version: &self.version,
+                url: None,
+            }
+        }
     }
 }
 
 impl From<&AnnotatedDist> for RequirementsTxtDist {
     fn from(annotated: &AnnotatedDist) -> Self {
         Self {
             dist: annotated.dist.clone(),
+            version: annotated.version.clone(),
             extras: if let Some(extra) = annotated.extra.clone() {
                 vec![extra]
             } else {
@@ -155,7 +170,13 @@ impl From<&AnnotatedDist> for RequirementsTxtDist {
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
 pub(crate) enum RequirementsTxtComparator<'a> {
     Url(Cow<'a, str>),
-    Name(&'a PackageName),
+    /// In universal mode, we can have multiple versions for a package, so we track the version and
+    /// the URL (for non-index packages) to have a stable sort for those, too.
+    Name {
+        name: &'a PackageName,
+        version: &'a Version,
+        url: Option<Cow<'a, str>>,
+    },
 }
 
 impl Name for RequirementsTxtDist {

crates/uv/tests/pip_compile.rs

@@ -7250,13 +7250,13 @@ fn universal_nested_overlapping_local_requirement() -> Result<()> {
         # via torch
     tbb==2021.11.0 ; platform_machine != 'x86_64' and platform_system == 'Windows'
         # via mkl
-    torch==2.3.0 ; platform_machine != 'x86_64'
-        # via -r requirements.in
     torch==2.0.0+cu118 ; platform_machine == 'x86_64'
         # via
         #   -r requirements.in
         #   example
         #   triton
+    torch==2.3.0 ; platform_machine != 'x86_64'
+        # via -r requirements.in
     triton==2.0.0 ; platform_machine == 'x86_64' and platform_system == 'Linux'
         # via torch
     typing-extensions==4.10.0
@@ -7324,13 +7324,13 @@ fn universal_nested_overlapping_local_requirement() -> Result<()> {
         # via torch
     tbb==2021.11.0 ; platform_machine != 'x86_64' and platform_system == 'Windows'
         # via mkl
-    torch==2.3.0 ; platform_machine != 'x86_64'
-        # via -r requirements.in
     torch==2.0.0+cu118 ; platform_machine == 'x86_64'
         # via
         #   -r requirements.in
         #   example
         #   triton
+    torch==2.3.0 ; platform_machine != 'x86_64'
+        # via -r requirements.in
     triton==2.0.0 ; platform_machine == 'x86_64' and platform_system == 'Linux'
         # via torch
     typing-extensions==4.10.0
@@ -7440,17 +7440,17 @@ fn universal_nested_disjoint_local_requirement() -> Result<()> {
         # via torch
     tbb==2021.11.0 ; os_name != 'Linux' and platform_system == 'Windows'
         # via mkl
+    torch==2.0.0+cpu ; os_name == 'Linux'
+        # via
+        #   -r requirements.in
+        #   example
     torch==2.0.0+cu118 ; os_name == 'Linux'
         # via
         #   -r requirements.in
         #   example
         #   triton
     torch==2.3.0 ; os_name != 'Linux'
         # via -r requirements.in
-    torch==2.0.0+cpu ; os_name == 'Linux'
-        # via
-        #   -r requirements.in
-        #   example
     triton==2.0.0 ; os_name == 'Linux' and platform_machine == 'x86_64' and platform_system == 'Linux'
         # via torch
     typing-extensions==4.10.0