feat: Support PEP508 environment markers

crates/pixi/tests/integration_rust/add_tests.rs

@@ -544,7 +544,8 @@ index-url = "{index_url}"
                         source: PixiPypiSource::Registry {
                             version: VersionOrStar::from_str("==24.8.0").unwrap(),
                             index: None,
-                        }
+                        },
+                        env_markers: pep508_rs::MarkerTree::default(),
                     }
                 );
             }

crates/pixi/tests/integration_rust/pypi_tests.rs

@@ -96,6 +96,83 @@ test = {{features = ["test"]}}
     );
 }
 
+#[tokio::test]
+async fn pyproject_environment_markers_resolved() {
+    setup_tracing();
+
+    // Add a dependency that's present only on linux-64
+    let simple = PyPIDatabase::new()
+        .with(PyPIPackage::new("nvidia-nccl-cu12", "1.0.0").with_tag(
+            "cp311",
+            "cp311",
+            "manylinux1_x86_64",
+        ))
+        .into_simple_index()
+        .unwrap();
+
+    // Create a TOML with two platforms
+    let platform1 = Platform::Linux64;
+    let platform2 = Platform::OsxArm64;
+    let platform_str = format!("\"{}\", \"{}\"", platform1, platform2);
+
+    let mut package_db = MockRepoData::default();
+    package_db.add_package(
+        Package::build("python", "3.11.0")
+            .with_subdir(platform1)
+            .finish(),
+    );
+    package_db.add_package(
+        Package::build("python", "3.11.0")
+            .with_subdir(platform2)
+            .finish(),
+    );
+    let channel = package_db.into_channel().await.unwrap();
+    let channel_url = channel.url();
+    let index_url = simple.index_url();
+
+    // Make sure that the TOML contains an env marker to allow linux-64.
+    let pyproject = format!(
+        r#"
+[build-system]
+requires = ["setuptools"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "environment-markers"
+dependencies = [
+    "nvidia-nccl-cu12; sys_platform == 'linux'"
+]
+
+[tool.pixi.workspace]
+channels = ["{channel_url}"]
+platforms = [{platform_str}]
+conda-pypi-map = {{}}
+
+[tool.pixi.dependencies]
+python = "==3.11.0"
+
+[tool.pixi.pypi-options]
+index-url = "{index_url}"
+"#,
+    );
+
+    let pixi = PixiControl::from_pyproject_manifest(&pyproject).unwrap();
+
+    let lock = pixi.update_lock_file().await.unwrap();
+
+    let nccl_req = Requirement::from_str("nvidia-nccl-cu12; sys_platform == 'linux'").unwrap();
+    // Check that the requirement is present in the lockfile for linux-64
+    assert!(
+        lock.contains_pep508_requirement("default", platform1, nccl_req.clone()),
+        "default environment should include nccl for linux-64"
+    );
+    // But not for osx-arm64
+    assert!(
+        !lock.contains_pep508_requirement("default", platform2, nccl_req.clone()),
+        "default environment shouldn't include nccl for osx-64"
+    );
+}
+
 #[tokio::test]
 async fn test_flat_links_based_index_returns_path() {
     setup_tracing();

crates/pixi_cli/src/upgrade.rs

@@ -5,7 +5,7 @@ use fancy_display::FancyDisplay;
 use indexmap::{IndexMap, IndexSet};
 use itertools::Itertools;
 use miette::{IntoDiagnostic, MietteDiagnostic, WrapErr};
-use pep508_rs::{MarkerTree, Requirement};
+use pep508_rs::Requirement;
 use pixi_config::ConfigCli;
 use pixi_core::{
     WorkspaceLocator,
@@ -473,8 +473,7 @@ pub fn parse_specs_for_platform(
                 Requirement {
                     name: name.as_normalized().clone(),
                     extras: req.extras.clone(),
-                    // TODO: Add marker support here to avoid overwriting existing markers
-                    marker: MarkerTree::default(),
+                    marker: req.env_markers.clone(),
                     origin: None,
                     version_or_url: None,
                 },

crates/pixi_cli/src/workspace/export/conda_environment.rs

@@ -50,8 +50,9 @@ fn format_pip_extras(extras: &[ExtraName]) -> String {
 
 fn format_pip_dependency(name: &PypiPackageName, requirement: &PixiPypiSpec) -> String {
     let extras = &requirement.extras;
+    let markers = &requirement.env_markers;
 
-    match &requirement.source {
+    let mut dependency = match &requirement.source {
         PixiPypiSource::Git { git: git_url } => {
             let mut git_string = format!(
                 "{name}{extras} @ git+{url}",
@@ -115,7 +116,14 @@ fn format_pip_dependency(name: &PypiPackageName, requirement: &PixiPypiSpec) ->
                 extras = format_pip_extras(extras)
             ),
         },
+    };
+
+    let marker_str = markers.try_to_string();
+    if let Some(marker_str) = marker_str {
+        dependency.push_str(&format!("; {}", marker_str));
     }
+
+    dependency
 }
 
 fn build_env_yaml(

crates/pixi_core/src/lock_file/resolve/pypi.rs

@@ -347,15 +347,6 @@ pub async fn resolve_pypi(
         tracing::info!("there are no python packages installed by conda");
     }
 
-    let mut requirements = dependencies
-        .into_iter()
-        .flat_map(|(name, req)| {
-            req.into_iter()
-                .map(move |r| as_uv_req(&r, name.as_ref(), project_root))
-        })
-        .collect::<Result<Vec<_>, _>>()
-        .into_diagnostic()?;
-
     // Determine the python interpreter that is installed as part of the conda
     // packages.
     let python_record = locked_pixi_records
@@ -371,6 +362,16 @@ pub async fn resolve_pypi(
     // Construct the marker environment for the target platform
     let marker_environment = determine_marker_environment(platform, python_record.as_ref())?;
 
+    let mut requirements = dependencies
+        .into_iter()
+        .flat_map(|(name, req)| {
+            req.into_iter()
+                .map(move |r| as_uv_req(&r, name.as_ref(), project_root))
+        })
+        .filter_ok(|uv_req| uv_req.evaluate_markers(Some(&marker_environment), &uv_req.extras))
+        .collect::<Result<Vec<_>, _>>()
+        .into_diagnostic()?;
+
     // Determine the tags for this particular solve.
     let tags = get_pypi_tags(platform, &system_requirements, python_record.as_ref())?;
 

crates/pixi_core/src/lock_file/satisfiability/mod.rs

@@ -1506,22 +1506,56 @@ pub(crate) async fn verify_package_platform_satisfiability(
         })
         .collect::<Result<indexmap::IndexMap<_, _>, _>>()?;
 
+    // Find the python interpreter from the list of conda packages. Note that this
+    // refers to the locked python interpreter, it might not match the specs
+    // from the environment. That is ok because we will find that out when we
+    // check all the records.
+    let python_interpreter_record = locked_pixi_records.python_interpreter_record();
+
+    // Determine the marker environment from the python interpreter package.
+    let marker_environment = python_interpreter_record
+        .map(|interpreter| determine_marker_environment(platform, &interpreter.package_record))
+        .transpose()
+        .map_err(|err| {
+            Box::new(PlatformUnsat::FailedToDetermineMarkerEnvironment(
+                err.into(),
+            ))
+        });
+
+    let pypi_dependencies = environment.pypi_dependencies(Some(platform));
+
+    // We cannot determine the marker environment, for example if installing
+    // `wasm32` dependencies. However, it also doesn't really matter if we don't
+    // have any pypi requirements.
+    let marker_environment = match marker_environment {
+        Err(err) => {
+            if !pypi_dependencies.is_empty() {
+                return Err(err);
+            } else {
+                None
+            }
+        }
+        Ok(marker_environment) => marker_environment,
+    };
+
     // Transform from PyPiPackage name into UV Requirement type
-    let pypi_requirements = environment
-        .pypi_dependencies(Some(platform))
+    let pypi_requirements = pypi_dependencies
         .iter()
         .flat_map(|(name, reqs)| {
-            reqs.iter().map(move |req| {
-                Ok::<Dependency, Box<PlatformUnsat>>(Dependency::PyPi(
-                    as_uv_req(req, name.as_source(), project_root).map_err(|e| {
-                        Box::new(PlatformUnsat::AsPep508Error(
-                            name.as_normalized().clone(),
-                            e,
-                        ))
-                    })?,
-                    "<environment>".into(),
-                ))
-            })
+            reqs.iter()
+                .map(|req| as_uv_req(req, name.as_source(), project_root))
+                .filter_ok(|req| req.evaluate_markers(marker_environment.as_ref(), &req.extras))
+                .map(move |req| {
+                    Ok::<Dependency, Box<PlatformUnsat>>(Dependency::PyPi(
+                        req.map_err(|e| {
+                            Box::new(PlatformUnsat::AsPep508Error(
+                                name.as_normalized().clone(),
+                                e,
+                            ))
+                        })?,
+                        "<environment>".into(),
+                    ))
+                })
         })
         .collect::<Result<Vec<_>, _>>()?;
 
@@ -1605,36 +1639,6 @@ pub(crate) async fn verify_package_platform_satisfiability(
         return Err(Box::new(PlatformUnsat::TooManyCondaPackages(Vec::new())));
     }
 
-    // Find the python interpreter from the list of conda packages. Note that this
-    // refers to the locked python interpreter, it might not match the specs
-    // from the environment. That is ok because we will find that out when we
-    // check all the records.
-    let python_interpreter_record = locked_pixi_records.python_interpreter_record();
-
-    // Determine the marker environment from the python interpreter package.
-    let marker_environment = python_interpreter_record
-        .map(|interpreter| determine_marker_environment(platform, &interpreter.package_record))
-        .transpose()
-        .map_err(|err| {
-            Box::new(PlatformUnsat::FailedToDetermineMarkerEnvironment(
-                err.into(),
-            ))
-        });
-
-    // We cannot determine the marker environment, for example if installing
-    // `wasm32` dependencies. However, it also doesn't really matter if we don't
-    // have any pypi requirements.
-    let marker_environment = match marker_environment {
-        Err(err) => {
-            if !pypi_requirements.is_empty() {
-                return Err(err);
-            } else {
-                None
-            }
-        }
-        Ok(marker_environment) => marker_environment,
-    };
-
     // Determine the pypi packages provided by the locked conda packages.
     let locked_conda_pypi_packages = locked_pixi_records
         .by_pypi_name()

crates/pixi_core/src/lock_file/satisfiability/snapshots/pixi_core__lock_file__satisfiability__tests__failing_satisiability@changed-env-marker.snap

@@ -0,0 +1,7 @@
+---
+source: crates/pixi_core/src/lock_file/satisfiability/mod.rs
+expression: s
+---
+environment 'default' does not satisfy the requirements of the project for platform 'osx-arm64'
+    Diagnostic severity: error
+    Caused by: the requirement 'numpy==2.* ; sys_platform == 'darwin'' could not be satisfied (required by '<environment>')