uv-resolver: error during installation for conflicting extras

This collects ALL activated extras while traversing the lock file to
produce a `Resolution` for installation. If any two extras are activated
that are conflicting, then an error is produced.

We add a couple of tests to demonstrate the behavior. One case is
desirable (where we conditionally depend on `package[extra]`) and the
other case is undesirable (where we create an uninstallable lock file).

Fixes #9942, Fixes #10590

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

@@ -1,9 +1,11 @@
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
+use std::collections::BTreeSet;
 use std::collections::VecDeque;
 use std::path::Path;
 
 use either::Either;
+use itertools::Itertools;
 use petgraph::Graph;
 use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};
 
@@ -265,6 +267,8 @@ pub trait Installable<'lock> {
             }
         }
 
+        let mut all_activated_extras: BTreeSet<(&PackageName, &ExtraName)> =
+            activated_extras.iter().copied().collect();
         while let Some((package, extra)) = queue.pop_front() {
             let deps = if let Some(extra) = extra {
                 Either::Left(
@@ -283,6 +287,7 @@ pub trait Installable<'lock> {
                     let mut extended = activated_extras.to_vec();
                     for extra in &dep.extra {
                         extended.push((&dep.package_id.name, extra));
+                        all_activated_extras.insert((&dep.package_id.name, extra));
                     }
                     activated_extras = Cow::Owned(extended);
                 }
@@ -338,6 +343,32 @@ pub trait Installable<'lock> {
             }
         }
 
+        // At time of writing, it's somewhat expected that the set of
+        // conflicting extras is pretty small. With that said, the
+        // time complexity of the following routine is pretty gross.
+        // Namely, `set.contains` is linear in the size of the set,
+        // iteration over all conflicts is also obviously linear in
+        // the number of conflicting sets and then for each of those,
+        // we visit every possible pair of activated extra from above,
+        // which is quadratic in the total number of extras enabled. I
+        // believe the simplest improvement here, if it's necessary, is
+        // to adjust the `Conflicts` internals to own these sorts of
+        // checks. ---AG
+        for set in self.lock().conflicts().iter() {
+            for ((pkg1, extra1), (pkg2, extra2)) in all_activated_extras.iter().tuple_combinations()
+            {
+                if set.contains(pkg1, *extra1) && set.contains(pkg2, *extra2) {
+                    return Err(LockErrorKind::ConflictingExtra {
+                        package1: (*pkg1).clone(),
+                        extra1: (*extra1).clone(),
+                        package2: (*pkg2).clone(),
+                        extra2: (*extra2).clone(),
+                    }
+                    .into());
+                }
+            }
+        }
+
         Ok(Resolution::new(petgraph))
     }
 

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

@@ -4897,6 +4897,16 @@ enum LockErrorKind {
         #[source]
         err: uv_distribution::Error,
     },
+    #[error(
+        "Found conflicting extras `{package1}[{extra1}]` \
+         and `{package2}[{extra2}]` enabled simultaneously"
+    )]
+    ConflictingExtra {
+        package1: PackageName,
+        extra1: ExtraName,
+        package2: PackageName,
+        extra2: ExtraName,
+    },
 }
 
 /// An error that occurs when a source string could not be parsed.

crates/uv/tests/it/lock_conflict.rs

@@ -1201,6 +1201,221 @@ fn extra_unconditional_non_conflicting() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn extra_unconditional_in_optional() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let root_pyproject_toml = context.temp_dir.child("pyproject.toml");
+    root_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        description = "Add your description here"
+        readme = "README.md"
+        requires-python = ">=3.10.0"
+        dependencies = []
+
+        [tool.uv.workspace]
+        members = ["proxy1"]
+
+        [tool.uv.sources]
+        proxy1 = { workspace = true }
+
+        [project.optional-dependencies]
+        x1 = ["proxy1[nested-x1]"]
+        x2 = ["proxy1[nested-x2]"]
+        "#,
+    )?;
+
+    let proxy1_pyproject_toml = context.temp_dir.child("proxy1").child("pyproject.toml");
+    proxy1_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "proxy1"
+        version = "0.1.0"
+        requires-python = ">=3.10.0"
+        dependencies = []
+
+        [project.optional-dependencies]
+        nested-x1 = ["sortedcontainers==2.3.0"]
+        nested-x2 = ["sortedcontainers==2.4.0"]
+
+        [tool.uv]
+        conflicts = [
+          [
+            { extra = "nested-x1" },
+            { extra = "nested-x2" },
+          ],
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    "###);
+
+    // This shouldn't install anything.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Audited in [TIME]
+    "###);
+
+    // This should install `sortedcontainers==2.3.0`.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen").arg("--extra=x1"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + sortedcontainers==2.3.0
+    "###);
+
+    // This should install `sortedcontainers==2.4.0`.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen").arg("--extra=x2"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Prepared 1 package in [TIME]
+    Uninstalled 1 package in [TIME]
+    Installed 1 package in [TIME]
+     - sortedcontainers==2.3.0
+     + sortedcontainers==2.4.0
+    "###);
+
+    // This should error!
+    uv_snapshot!(
+        context.filters(),
+        context.sync().arg("--frozen").arg("--extra=x1").arg("--extra=x2"),
+        @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Found conflicting extras `proxy1[nested-x1]` and `proxy1[nested-x2]` enabled simultaneously
+    "###);
+
+    Ok(())
+}
+
+#[test]
+fn extra_unconditional_non_local_conflict() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let root_pyproject_toml = context.temp_dir.child("pyproject.toml");
+    root_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        description = "Add your description here"
+        readme = "README.md"
+        requires-python = ">=3.10.0"
+        dependencies = ["a", "b"]
+
+        [tool.uv.workspace]
+        members = ["a", "b", "c"]
+
+        [tool.uv.sources]
+        a = { workspace = true }
+        b = { workspace = true }
+        c = { workspace = true }
+        "#,
+    )?;
+
+    let a_pyproject_toml = context.temp_dir.child("a").child("pyproject.toml");
+    a_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "a"
+        version = "0.1.0"
+        requires-python = ">=3.10.0"
+        dependencies = ["c[x1]"]
+
+        [tool.uv.sources]
+        c = { workspace = true }
+        "#,
+    )?;
+
+    let b_pyproject_toml = context.temp_dir.child("b").child("pyproject.toml");
+    b_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "b"
+        version = "0.1.0"
+        requires-python = ">=3.10.0"
+        dependencies = ["c[x2]"]
+
+        [tool.uv.sources]
+        c = { workspace = true }
+        "#,
+    )?;
+
+    let c_pyproject_toml = context.temp_dir.child("c").child("pyproject.toml");
+    c_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "c"
+        version = "0.1.0"
+        requires-python = ">=3.10.0"
+        dependencies = []
+
+        [project.optional-dependencies]
+        x1 = ["sortedcontainers==2.3.0"]
+        x2 = ["sortedcontainers==2.4.0"]
+
+        [tool.uv]
+        conflicts = [
+          [
+            { extra = "x1" },
+            { extra = "x2" },
+          ],
+        ]
+        "#,
+    )?;
+
+    // Regrettably, this produces a lock file, and it is one
+    // that can never be installed! Namely, because two different
+    // conflicting extras are enabled unconditionally in all
+    // configurations.
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    "###);
+
+    // This should fail. If it doesn't and we generated a lock
+    // file above, then this will likely result in the installation
+    // of two different versions of the same package.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Found conflicting extras `c[x1]` and `c[x2]` enabled simultaneously
+    "###);
+
+    Ok(())
+}
+
 /// This tests how we deal with mutually conflicting extras that span multiple
 /// packages in a workspace.
 #[test]