Skip installed Python check for URL dependencies

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

@@ -1230,36 +1230,21 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
 
         // The version is incompatible due to its `Requires-Python` requirement.
         if let Some(requires_python) = metadata.requires_python.as_ref() {
-            // TODO(charlie): We only care about this for source distributions.
-            if !python_requirement
-                .installed()
-                .is_contained_by(requires_python)
-            {
-                return Ok(Some(ResolverVersion::Unavailable(
-                    version.clone(),
-                    UnavailableVersion::IncompatibleDist(IncompatibleDist::Source(
-                        IncompatibleSource::RequiresPython(
-                            requires_python.clone(),
-                            PythonRequirementKind::Installed,
-                        ),
-                    )),
-                )));
-            }
             if !python_requirement.target().is_contained_by(requires_python) {
+                let kind = if python_requirement.installed() == python_requirement.target() {
+                    PythonRequirementKind::Installed
+                } else {
+                    PythonRequirementKind::Target
+                };
                 return Ok(Some(ResolverVersion::Unavailable(
                     version.clone(),
                     UnavailableVersion::IncompatibleDist(IncompatibleDist::Source(
-                        IncompatibleSource::RequiresPython(
-                            requires_python.clone(),
-                            PythonRequirementKind::Target,
-                        ),
+                        IncompatibleSource::RequiresPython(requires_python.clone(), kind),
                     )),
                 )));
             }
         }
 
-        // If this is a wheel, and the implied Python version doesn't overlap, raise an error.
-
         Ok(Some(ResolverVersion::Unforked(version.clone())))
     }
 

crates/uv/tests/it/lock.rs

@@ -32845,6 +32845,66 @@ fn lock_path_dependency_no_index() -> Result<()> {
     Ok(())
 }
 
+/// Lock a project with a local path dependency gated behind a Python version marker, where the
+/// child's `requires-python` is stricter than the root but compatible with the marker.
+///
+/// See: <https://github.com/astral-sh/uv/issues/18199>
+#[test]
+fn lock_path_dependency_marker_gated_requires_python() -> Result<()> {
+    // Use Python 3.9 as the interpreter to reproduce the issue: the installed Python (3.9)
+    // does not satisfy the child's `requires-python = ">=3.12"`, but the child is gated
+    // behind `python_version >= '3.12'`, so it should still resolve.
+    let context = uv_test::test_context!("3.9");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.9"
+        dependencies = ["child; python_version >= '3.12'"]
+
+        [tool.uv.sources]
+        child = { path = "./child" }
+        "#,
+    )?;
+
+    let child = context.temp_dir.child("child");
+    child.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["iniconfig"]
+        "#,
+    )?;
+
+    // The lock should succeed: the child is only required for Python >= 3.12, so its
+    // `requires-python = ">=3.12"` is compatible with the fork.
+    uv_snapshot!(context.filters(), context.lock(), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    ");
+
+    // Re-lock with `--refresh` should also succeed.
+    uv_snapshot!(context.filters(), context.lock().arg("--refresh"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    ");
+
+    Ok(())
+}
+
 /// Test that a nested path dependency with an explicit index validates correctly.
 #[tokio::test]
 async fn lock_nested_path_dependency_explicit_index() -> Result<()> {

crates/uv/tests/it/pip_compile.rs

@@ -11067,28 +11067,73 @@ requires-python = ">=3.13"
     let requirements_in = context.temp_dir.child("requirements.in");
     requirements_in.write_str(&format!("-e {}", editable_dir.path().display()))?;
 
-    let filters: Vec<_> = [
-        // 3.11 may not be installed
-        (
-            "warning: The requested Python version 3.11 is not available; .* will be used to build dependencies instead.\n",
-            "",
-        ),
-    ]
-        .into_iter()
-        .chain(context.filters())
-        .collect();
-
-    uv_snapshot!(filters, context.pip_compile()
+    uv_snapshot!(context.filters(), context.pip_compile()
         .arg("requirements.in")
         .arg("--python-version=3.11"), @"
     success: false
     exit_code: 1
     ----- stdout -----
 
     ----- stderr -----
+    warning: The requested Python version 3.11 is not available; 3.12.[X] will be used to build dependencies instead.
       × No solution found when resolving dependencies:
-      ╰─▶ Because the current Python version (3.12.[X]) does not satisfy Python>=3.13 and example==0.0.0 depends on Python>=3.13, we can conclude that example==0.0.0 cannot be used.
+      ╰─▶ Because the requested Python version (>=3.11) does not satisfy Python>=3.13 and example==0.0.0 depends on Python>=3.13, we can conclude that example==0.0.0 cannot be used.
           And because only example==0.0.0 is available and you require example, we can conclude that your requirements are unsatisfiable.
+
+          hint: The `--python-version` value (>=3.11) includes Python versions that are not supported by your dependencies (e.g., example==0.0.0 only supports >=3.13). Consider using a higher `--python-version` value.
+    "
+    );
+
+    Ok(())
+}
+
+/// Resolve successfully when an editable's `Requires-Python` is satisfied by
+/// `--python-version` but not by the installed interpreter.
+#[test]
+fn requires_python_editable_installed_incompatible() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+
+    // Create an editable package with `requires-python >= 3.13`.
+    let editable_dir = context.temp_dir.child("editable");
+    editable_dir.create_dir_all()?;
+    let pyproject_toml = editable_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"[project]
+name = "example"
+version = "0.0.0"
+dependencies = [
+  "anyio==4.0.0"
+]
+requires-python = ">=3.13"
+"#,
+    )?;
+
+    // Write to a requirements file.
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str(&format!("-e {}", editable_dir.path().display()))?;
+
+    // `--python-version 3.13` satisfies `requires-python >= 3.13`, so resolution succeeds
+    // even though the installed interpreter is 3.12.
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("requirements.in")
+        .arg("--python-version=3.13"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version=3.13
+    -e [TEMP_DIR]/editable
+        # via -r requirements.in
+    anyio==4.0.0
+        # via example
+    idna==3.6
+        # via anyio
+    sniffio==1.3.1
+        # via anyio
+
+    ----- stderr -----
+    warning: The requested Python version 3.13 is not available; 3.12.[X] will be used to build dependencies instead.
+    Resolved 4 packages in [TIME]
     "
     );
 

crates/uv/tests/it/pip_install.rs

@@ -5247,6 +5247,82 @@ requires-python = ">=3.13"
     Ok(())
 }
 
+/// Resolve successfully when `--python-version` satisfies `Requires-Python` but the installed
+/// interpreter does not. The `installed()` check is not applied in the resolver — the resolution
+/// target is what matters.
+#[test]
+fn requires_python_source_dist_installed_incompatible() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+
+    // Create a source distribution with `requires-python >= 3.13`.
+    let child_dir = context.temp_dir.child("child");
+    child_dir.create_dir_all()?;
+    child_dir.child("pyproject.toml").write_str(
+        r#"[project]
+name = "example"
+version = "0.0.0"
+dependencies = []
+requires-python = ">=3.13"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+"#,
+    )?;
+    child_dir.child("src").child("example").create_dir_all()?;
+    child_dir
+        .child("src")
+        .child("example")
+        .child("__init__.py")
+        .touch()?;
+
+    // `--python-version 3.13` satisfies `requires-python >= 3.13`, so resolution succeeds
+    // even though the installed interpreter is 3.12.
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--python-version=3.13")
+        .arg(child_dir.path()), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + example==0.0.0 (from file://[TEMP_DIR]/child)
+    "
+    );
+
+    Ok(())
+}
+
+/// Like [`requires_python_source_dist_installed_incompatible`], but using a registry package
+/// (`iniconfig`) instead of a direct URL, with `--no-binary` to force building from source.
+#[test]
+fn requires_python_source_dist_installed_incompatible_registry() {
+    let context = uv_test::test_context!("3.9").with_exclude_newer("2025-11-01T00:00:00Z");
+
+    // `--python-version 3.10` satisfies `requires-python >= 3.10`, so resolution succeeds
+    // even though the installed interpreter is 3.9. This should arguably fail, and some build
+    // backends would likely error in this scenario.
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--python-version=3.10")
+        .arg("--no-binary")
+        .arg("iniconfig")
+        .arg("iniconfig==2.3.0"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.3.0
+    "
+    );
+}
+
 /// Install with `--no-build-isolation`, to disable isolation during PEP 517 builds.
 #[test]
 fn no_build_isolation() -> Result<()> {