Respect tool.uv.environments in pip compile --universal (#6663)

## Summary

We now respect the `environments` field in `uv pip compile --universal`,
e.g.:

```toml
[tool.uv]
environments = ["platform_system == 'Emscripten'"]
```

Closes https://github.com/astral-sh/uv/issues/6641.

crates/uv-workspace/src/environments.rs

@@ -1,78 +0,0 @@
-use std::str::FromStr;
-
-use serde::ser::SerializeSeq;
-
-use pep508_rs::MarkerTree;
-
-#[derive(Debug, Default, Clone, Eq, PartialEq)]
-pub struct SupportedEnvironments(Vec<MarkerTree>);
-
-impl SupportedEnvironments {
-    /// Return the list of marker trees.
-    pub fn as_markers(&self) -> &[MarkerTree] {
-        &self.0
-    }
-
-    /// Convert the [`SupportedEnvironments`] struct into a list of marker trees.
-    pub fn into_markers(self) -> Vec<MarkerTree> {
-        self.0
-    }
-}
-
-/// Serialize a [`SupportedEnvironments`] struct into a list of marker strings.
-impl serde::Serialize for SupportedEnvironments {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: serde::Serializer,
-    {
-        let mut seq = serializer.serialize_seq(Some(self.0.len()))?;
-        for element in &self.0 {
-            if let Some(contents) = element.contents() {
-                seq.serialize_element(&contents)?;
-            }
-        }
-        seq.end()
-    }
-}
-
-/// Deserialize a marker string or list of marker strings into a [`SupportedEnvironments`] struct.
-impl<'de> serde::Deserialize<'de> for SupportedEnvironments {
-    fn deserialize<D>(deserializer: D) -> Result<SupportedEnvironments, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        struct StringOrVecVisitor;
-
-        impl<'de> serde::de::Visitor<'de> for StringOrVecVisitor {
-            type Value = SupportedEnvironments;
-
-            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
-                formatter.write_str("a string or a list of strings")
-            }
-
-            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
-            where
-                E: serde::de::Error,
-            {
-                let marker = MarkerTree::from_str(value).map_err(serde::de::Error::custom)?;
-                Ok(SupportedEnvironments(vec![marker]))
-            }
-
-            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
-            where
-                A: serde::de::SeqAccess<'de>,
-            {
-                let mut markers = Vec::new();
-
-                while let Some(elem) = seq.next_element::<String>()? {
-                    let marker = MarkerTree::from_str(&elem).map_err(serde::de::Error::custom)?;
-                    markers.push(marker);
-                }
-
-                Ok(SupportedEnvironments(markers))
-            }
-        }
-
-        deserializer.deserialize_any(StringOrVecVisitor)
-    }
-}

crates/uv-workspace/src/lib.rs

@@ -1,10 +1,8 @@
-pub use environments::SupportedEnvironments;
 pub use workspace::{
     check_nested_workspaces, DiscoveryOptions, ProjectWorkspace, VirtualProject, Workspace,
     WorkspaceError, WorkspaceMember,
 };
 
-mod environments;
 pub mod pyproject;
 pub mod pyproject_mut;
 mod workspace;

crates/uv-workspace/src/pyproject.rs

@@ -14,9 +14,8 @@ use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use url::Url;
 
-use crate::environments::SupportedEnvironments;
 use pep440_rs::VersionSpecifiers;
-use pypi_types::{RequirementSource, VerbatimParsedUrl};
+use pypi_types::{RequirementSource, SupportedEnvironments, VerbatimParsedUrl};
 use uv_git::GitReference;
 use uv_macros::OptionsMetadata;
 use uv_normalize::{ExtraName, PackageName};
@@ -121,11 +120,14 @@ pub struct ToolUv {
     /// By default, uv will resolve for all possible environments during a `uv lock` operation.
     /// However, you can restrict the set of supported environments to improve performance and avoid
     /// unsatisfiable branches in the solution space.
+    ///
+    /// These environments will also respected when `uv pip compile` is invoked with the
+    /// `--universal` flag.
     #[cfg_attr(
         feature = "schemars",
         schemars(
             with = "Option<Vec<String>>",
-            description = "A list of environment markers, e.g. `python_version >= '3.6'`."
+            description = "A list of environment markers, e.g., `python_version >= '3.6'`."
         )
     )]
     #[option(

crates/uv-workspace/src/workspace.rs

@@ -9,12 +9,11 @@ use rustc_hash::FxHashSet;
 use tracing::{debug, trace, warn};
 
 use pep508_rs::{MarkerTree, RequirementOrigin, VerbatimUrl};
-use pypi_types::{Requirement, RequirementSource, VerbatimParsedUrl};
+use pypi_types::{Requirement, RequirementSource, SupportedEnvironments, VerbatimParsedUrl};
 use uv_fs::Simplified;
 use uv_normalize::{GroupName, PackageName, DEV_DEPENDENCIES};
 use uv_warnings::warn_user;
 
-use crate::environments::SupportedEnvironments;
 use crate::pyproject::{Project, PyProjectToml, Source, ToolUvWorkspace};
 
 #[derive(thiserror::Error, Debug)]