Respect dependency group markers in `uv export` (#8659)

## Summary

Closes https://github.com/astral-sh/uv/issues/8658.

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

@@ -22,18 +22,12 @@ use crate::graph_ops::marker_reachability;
 use crate::lock::{Package, PackageId, Source};
 use crate::{Lock, LockError};
 
-type LockGraph<'lock> = Graph<&'lock Package, Edge, Directed>;
+type LockGraph<'lock> = Graph<Node<'lock>, Edge, Directed>;
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-struct Node<'lock> {
-    package: &'lock Package,
-    marker: MarkerTree,
-}
 
 /// An export of a [`Lock`] that renders in `requirements.txt` format.
 #[derive(Debug)]
 pub struct RequirementsTxtExport<'lock> {
-    nodes: Vec<Node<'lock>>,
+    nodes: Vec<Requirement<'lock>>,
     hashes: bool,
     editable: EditableMode,
 }
@@ -55,45 +49,62 @@ impl<'lock> RequirementsTxtExport<'lock> {
         let mut queue: VecDeque<(&Package, Option<&ExtraName>)> = VecDeque::new();
         let mut seen = FxHashSet::default();
 
+        let root = petgraph.add_node(Node::Root);
+
         // Add the workspace package to the queue.
-        let root = lock
+        let dist = lock
             .find_by_name(root_name)
             .expect("found too many packages matching root")
             .expect("could not find root");
 
         if dev.prod() {
-            // Add the base package.
+            // Add the workspace package to the graph.
-            queue.push_back((root, None));
+            if let Entry::Vacant(entry) = inverse.entry(&dist.id) {
+                entry.insert(petgraph.add_node(Node::Package(dist)));
+            }
 
-            // Add any extras.
+            // Add an edge from the root.
+            let index = inverse[&dist.id];
+            petgraph.add_edge(root, index, MarkerTree::TRUE);
+
+            // Push its dependencies on the queue.
+            queue.push_back((dist, None));
             match extras {
                 ExtrasSpecification::None => {}
                 ExtrasSpecification::All => {
-                    for extra in root.optional_dependencies.keys() {
+                    for extra in dist.optional_dependencies.keys() {
-                        queue.push_back((root, Some(extra)));
+                        queue.push_back((dist, Some(extra)));
                     }
                 }
                 ExtrasSpecification::Some(extras) => {
                     for extra in extras {
-                        queue.push_back((root, Some(extra)));
+                        queue.push_back((dist, Some(extra)));
+                    }
                 }
             }
         }
 
-            // Add the root package to the graph.
+        // Add any development dependencies.
-            inverse.insert(&root.id, petgraph.add_node(root));
-        }
-
-        // Add any dev dependencies.
         for group in dev.iter() {
-            for dep in root.dependency_groups.get(group).into_iter().flatten() {
+            for dep in dist.dependency_groups.get(group).into_iter().flatten() {
                 let dep_dist = lock.find_by_id(&dep.package_id);
 
                 // Add the dependency to the graph.
                 if let Entry::Vacant(entry) = inverse.entry(&dep.package_id) {
-                    entry.insert(petgraph.add_node(dep_dist));
+                    entry.insert(petgraph.add_node(Node::Package(dep_dist)));
                 }
 
+                // Add an edge from the root. Development dependencies may be installed without
+                // installing the workspace package itself (which can never have markers on it
+                // anyway), so they're directly connected to the root.
+                let dep_index = inverse[&dep.package_id];
+                petgraph.add_edge(
+                    root,
+                    dep_index,
+                    dep.simplified_marker.as_simplified_marker_tree().clone(),
+                );
+
+                // Push its dependencies on the queue.
                 if seen.insert((&dep.package_id, None)) {
                     queue.push_back((dep_dist, None));
                 }
@@ -126,7 +137,7 @@ impl<'lock> RequirementsTxtExport<'lock> {
 
                 // Add the dependency to the graph.
                 if let Entry::Vacant(entry) = inverse.entry(&dep.package_id) {
-                    entry.insert(petgraph.add_node(dep_dist));
+                    entry.insert(petgraph.add_node(Node::Package(dep_dist)));
                 }
 
                 // Add the edge.
@@ -152,12 +163,16 @@ impl<'lock> RequirementsTxtExport<'lock> {
         let mut reachability = marker_reachability(&petgraph, &[]);
 
         // Collect all packages.
-        let mut nodes: Vec<Node> = petgraph
+        let mut nodes = petgraph
             .node_references()
+            .filter_map(|(index, node)| match node {
+                Node::Root => None,
+                Node::Package(package) => Some((index, package)),
+            })
             .filter(|(_index, package)| {
                 install_options.include_package(&package.id.name, Some(root_name), lock.members())
             })
-            .map(|(index, package)| Node {
+            .map(|(index, package)| Requirement {
                 package,
                 marker: reachability.remove(&index).unwrap_or_default(),
             })
@@ -165,7 +180,7 @@ impl<'lock> RequirementsTxtExport<'lock> {
 
         // Sort the nodes, such that unnamed URLs (editables) appear at the top.
         nodes.sort_unstable_by(|a, b| {
-            NodeComparator::from(a.package).cmp(&NodeComparator::from(b.package))
+            RequirementComparator::from(a.package).cmp(&RequirementComparator::from(b.package))
         });
 
         Ok(Self {
@@ -179,7 +194,7 @@ impl<'lock> RequirementsTxtExport<'lock> {
 impl std::fmt::Display for RequirementsTxtExport<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         // Write out each package.
-        for Node { package, marker } in &self.nodes {
+        for Requirement { package, marker } in &self.nodes {
             match &package.id.source {
                 Source::Registry(_) => {
                     write!(f, "{}=={}", package.id.name, package.id.version)?;
@@ -261,17 +276,31 @@ impl std::fmt::Display for RequirementsTxtExport<'_> {
     }
 }
 
+/// A node in the [`LockGraph`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum Node<'lock> {
+    Root,
+    Package(&'lock Package),
+}
+
 /// The edges of the [`LockGraph`].
 type Edge = MarkerTree;
 
+/// A flat requirement, with its associated marker.
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Requirement<'lock> {
+    package: &'lock Package,
+    marker: MarkerTree,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
-enum NodeComparator<'lock> {
+enum RequirementComparator<'lock> {
     Editable(&'lock Path),
     Path(&'lock Path),
     Package(&'lock PackageId),
 }
 
-impl<'lock> From<&'lock Package> for NodeComparator<'lock> {
+impl<'lock> From<&'lock Package> for RequirementComparator<'lock> {
     fn from(value: &'lock Package) -> Self {
         match &value.id.source {
             Source::Path(path) | Source::Directory(path) => Self::Path(path),

crates/uv/tests/it/export.rs

@@ -1027,7 +1027,7 @@ fn export_group() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["typing-extensions"]
         [dependency-groups]
-        foo = ["anyio"]
+        foo = ["anyio ; sys_platform == 'darwin'"]
         bar = ["iniconfig"]
         dev = ["sniffio"]
         "#,
@@ -1072,10 +1072,10 @@ fn export_group() -> Result<()> {
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
     #    uv export --cache-dir [CACHE_DIR] --group foo
-    anyio==4.3.0 \
+    anyio==4.3.0 ; sys_platform == 'darwin' \
         --hash=sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6 \
         --hash=sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8
-    idna==3.6 \
+    idna==3.6 ; sys_platform == 'darwin' \
         --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
         --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
     sniffio==1.3.1 \
@@ -1095,10 +1095,10 @@ fn export_group() -> Result<()> {
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
     #    uv export --cache-dir [CACHE_DIR] --group foo --group bar
-    anyio==4.3.0 \
+    anyio==4.3.0 ; sys_platform == 'darwin' \
         --hash=sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6 \
         --hash=sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8
-    idna==3.6 \
+    idna==3.6 ; sys_platform == 'darwin' \
         --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
         --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
     iniconfig==2.0.0 \