re-enable conflicting extra/group tests and fix regression from #9540

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

@@ -7,8 +7,8 @@ use tracing::warn;
 use uv_normalize::{ExtraName, GroupName, PackageName};
 use uv_pep440::{Version, VersionSpecifiers};
 use uv_pypi_types::{
-    ParsedArchiveUrl, ParsedDirectoryUrl, ParsedGitUrl, ParsedPathUrl, ParsedUrl, Requirement,
-    RequirementSource, VerbatimParsedUrl,
+    Conflicts, ParsedArchiveUrl, ParsedDirectoryUrl, ParsedGitUrl, ParsedPathUrl, ParsedUrl,
+    Requirement, RequirementSource, VerbatimParsedUrl,
 };
 
 use crate::pubgrub::{PubGrubPackage, PubGrubPackageInner};
@@ -26,14 +26,40 @@ pub(crate) struct PubGrubDependency {
 
 impl PubGrubDependency {
     pub(crate) fn from_requirement<'a>(
+        conflicts: &Conflicts,
         requirement: &'a Requirement,
         dev: Option<&'a GroupName>,
         source_name: Option<&'a PackageName>,
     ) -> impl Iterator<Item = Self> + 'a {
         let iter = if requirement.extras.is_empty() {
             Either::Left(iter::once(None))
         } else {
-            Either::Right(requirement.extras.clone().into_iter().map(Some))
+            // This is crazy subtle, but if any of the extras in the
+            // requirement are part of a declared conflict, then we
+            // specifically need (at time of writing) to include the
+            // base package as a dependency. This results in both
+            // the base package and the extra package being sibling
+            // dependencies at the point in which forks are created
+            // base on conflicting extras. If the base package isn't
+            // present at that point, then it's impossible for the
+            // fork that excludes all conflicting extras to reach
+            // the non-extra dependency, which may be necessary for
+            // correctness.
+            //
+            // But why do we not include the base package in the first
+            // place? Well, that's part of an optimization[1].
+            //
+            // [1]: https://github.com/astral-sh/uv/pull/9540
+            let base = if requirement
+                .extras
+                .iter()
+                .any(|extra| conflicts.contains(&requirement.name, extra))
+            {
+                Either::Left(iter::once(None))
+            } else {
+                Either::Right(iter::empty())
+            };
+            Either::Right(base.chain(requirement.extras.clone().into_iter().map(Some)))
         };
 
         // Add the package, plus any extra variants.

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

@@ -1272,7 +1272,12 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                 requirements
                     .iter()
                     .flat_map(|requirement| {
-                        PubGrubDependency::from_requirement(requirement, None, None)
+                        PubGrubDependency::from_requirement(
+                            &self.conflicts,
+                            requirement,
+                            None,
+                            None,
+                        )
                     })
                     .collect()
             }
@@ -1460,7 +1465,12 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                 let mut dependencies: Vec<_> = requirements
                     .iter()
                     .flat_map(|requirement| {
-                        PubGrubDependency::from_requirement(requirement, dev.as_ref(), Some(name))
+                        PubGrubDependency::from_requirement(
+                            &self.conflicts,
+                            requirement,
+                            dev.as_ref(),
+                            Some(name),
+                        )
                     })
                     .collect();
 

crates/uv/tests/it/lock_conflict.rs

@@ -1,16 +1,8 @@
 use anyhow::Result;
-use assert_cmd::assert::OutputAssertExt;
 use assert_fs::prelude::*;
-use indoc::{formatdoc, indoc};
 use insta::assert_snapshot;
-use std::io::BufReader;
-use url::Url;
-
-use crate::common::{
-    self, build_vendor_links_url, decode_token, download_to_disk, packse_index_url, uv_snapshot,
-    venv_bin_path, TestContext,
-};
-use uv_fs::Simplified;
+
+use crate::common::{uv_snapshot, TestContext};
 use uv_static::EnvVars;
 
 // All of the tests in this file should use `tool.uv.conflicts` in some way.
@@ -1329,7 +1321,7 @@ fn extra_nested_across_workspace() -> Result<()> {
       × No solution found when resolving dependencies:
       ╰─▶ Because dummy[extra2] depends on proxy1[extra2] and only proxy1[extra2]==0.1.0 is available, we can conclude that dummy[extra2] depends on proxy1[extra2]==0.1.0. (1)
 
-          Because proxy1[extra1]==0.1.0 depends on anyio==4.1.0 and proxy1[extra2]==0.1.0 depends on anyio==4.2.0, we can conclude that proxy1[extra1]==0.1.0 and proxy1[extra2]==0.1.0 are incompatible.
+          Because proxy1[extra2]==0.1.0 depends on anyio==4.2.0 and proxy1[extra1]==0.1.0 depends on anyio==4.1.0, we can conclude that proxy1[extra1]==0.1.0 and proxy1[extra2]==0.1.0 are incompatible.
           And because we know from (1) that dummy[extra2] depends on proxy1[extra2]==0.1.0, we can conclude that dummy[extra2] and proxy1[extra1]==0.1.0 are incompatible.
           And because only proxy1[extra1]==0.1.0 is available and dummysub[extra1] depends on proxy1[extra1], we can conclude that dummysub[extra1] and dummy[extra2] are incompatible.
           And because your workspace requires dummy[extra2] and dummysub[extra1], we can conclude that your workspace's requirements are unsatisfiable.
@@ -1845,8 +1837,8 @@ fn mixed() -> Result<()> {
 
     ----- stderr -----
       × No solution found when resolving dependencies:
-      ╰─▶ Because project:group1 depends on sortedcontainers==2.3.0 and project[extra1] depends on sortedcontainers==2.4.0, we can conclude that project[extra1] and project:group1 are incompatible.
-          And because your project depends on project:group1 and your project requires project[extra1], we can conclude that your projects's requirements are unsatisfiable.
+      ╰─▶ Because project:group1 depends on sortedcontainers==2.3.0 and your project depends on project:group1, we can conclude that your project depends on sortedcontainers==2.3.0.
+          And because project[extra1] depends on sortedcontainers==2.4.0 and your project requires project[extra1], we can conclude that your projects's requirements are unsatisfiable.
     "###);
 
     // And now with the same extra/group configuration, we tell uv
@@ -2655,3 +2647,98 @@ fn multiple_sources_index_disjoint_extras_with_marker() -> Result<()> {
 
     Ok(())
 }
+
+/// Tests that forks excluding both conflicting extras are handled correctly.
+///
+/// This previously failed where running `uv sync` wouldn't install anything,
+/// despite `sniffio` being an unconditional dependency.
+#[test]
+fn non_optional_dependency_extra() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.11"
+        dependencies = [
+          "sniffio>=1",
+        ]
+
+        [project.optional-dependencies]
+        x1 = ["idna==3.5"]
+        x2 = ["idna==3.6"]
+
+        [tool.uv]
+        conflicts = [
+          [
+            {package = "project", extra = "x1"},
+            {package = "project", extra = "x2"},
+          ],
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + sniffio==1.3.1
+    "###);
+
+    Ok(())
+}
+
+/// Like `non_optional_dependency_extra`, but for groups.
+///
+/// This test never regressed, but we added it here to ensure it doesn't.
+#[test]
+fn non_optional_dependency_group() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.11"
+        dependencies = [
+          "sniffio>=1",
+        ]
+
+        [dependency-groups]
+        g1 = ["idna==3.5"]
+        g2 = ["idna==3.6"]
+
+        [tool.uv]
+        conflicts = [
+          [
+            {package = "project", group = "g1"},
+            {package = "project", group = "g2"},
+          ],
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + sniffio==1.3.1
+    "###);
+
+    Ok(())
+}

crates/uv/tests/it/main.rs

@@ -34,6 +34,9 @@ mod init;
 #[cfg(all(feature = "python", feature = "pypi"))]
 mod lock;
 
+#[cfg(all(feature = "python", feature = "pypi"))]
+mod lock_conflict;
+
 mod lock_scenarios;
 
 mod pip_check;