Remove uses of Option<MarkerTree> (#5978)

## Summary

Follow up to #5898. This should fix
some of the failures in #5887 where
`uv lock --locked` is failing due to `Some(true)` and `None` markers not
comparing equal.

crates/distribution-types/src/resolution.rs

@@ -1,4 +1,5 @@
 use distribution_filename::DistExtension;
+use pep508_rs::MarkerTree;
 use pypi_types::{HashDigest, Requirement, RequirementSource};
 use std::collections::BTreeMap;
 use uv_normalize::{ExtraName, GroupName, PackageName};
@@ -211,7 +212,7 @@ impl From<&ResolvedDist> for Requirement {
         Requirement {
             name: resolved_dist.name().clone(),
             extras: vec![],
-            marker: None,
+            marker: MarkerTree::TRUE,
             source,
             origin: None,
         }

crates/pep508-rs/src/lib.rs

@@ -56,7 +56,7 @@ pub use verbatim_url::{
 };
 
 mod cursor;
-mod marker;
+pub mod marker;
 mod origin;
 #[cfg(feature = "non-pep508-extensions")]
 mod unnamed;
@@ -149,7 +149,7 @@ pub struct Requirement<T: Pep508Url = VerbatimUrl> {
     /// The markers such as `python_version > "3.8"` in
     /// `requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8"`.
     /// Those are a nested and/or tree.
-    pub marker: Option<MarkerTree>,
+    pub marker: MarkerTree,
     /// The source file containing the requirement.
     pub origin: Option<RequirementOrigin>,
 }
@@ -190,7 +190,7 @@ impl<T: Pep508Url + Display> Display for Requirement<T> {
                 }
             }
         }
-        if let Some(marker) = self.marker.as_ref().and_then(MarkerTree::contents) {
+        if let Some(marker) = self.marker.contents() {
             write!(f, " ; {marker}")?;
         }
         Ok(())
@@ -256,10 +256,7 @@ impl PyRequirement {
     /// `requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8"`
     #[getter]
     pub fn marker(&self) -> Option<String> {
-        self.marker
-            .as_ref()
-            .and_then(MarkerTree::contents)
-            .map(|marker| marker.to_string())
+        self.marker.try_to_string()
     }
 
     /// Parses a PEP 440 string
@@ -375,11 +372,7 @@ impl PyRequirement {
 impl<T: Pep508Url> Requirement<T> {
     /// Returns whether the markers apply for the given environment
     pub fn evaluate_markers(&self, env: &MarkerEnvironment, extras: &[ExtraName]) -> bool {
-        if let Some(marker) = &self.marker {
-            marker.evaluate(env, extras)
-        } else {
-            true
-        }
+        self.marker.evaluate(env, extras)
     }
 
     /// Returns whether the requirement would be satisfied, independent of environment markers, i.e.
@@ -393,11 +386,8 @@ impl<T: Pep508Url> Requirement<T> {
         extras: &HashSet<ExtraName>,
         python_versions: &[Version],
     ) -> bool {
-        if let Some(marker) = &self.marker {
-            marker.evaluate_extras_and_python_version(extras, python_versions)
-        } else {
-            true
-        }
+        self.marker
+            .evaluate_extras_and_python_version(extras, python_versions)
     }
 
     /// Returns whether the markers apply for the given environment.
@@ -406,38 +396,22 @@ impl<T: Pep508Url> Requirement<T> {
         env: &MarkerEnvironment,
         extras: &[ExtraName],
     ) -> (bool, Vec<MarkerWarning>) {
-        if let Some(marker) = &self.marker {
-            marker.evaluate_collect_warnings(env, extras)
-        } else {
-            (true, Vec::new())
-        }
+        self.marker.evaluate_collect_warnings(env, extras)
     }
 
     /// Return the requirement with an additional marker added, to require the given extra.
     ///
     /// For example, given `flask >= 2.0.2`, calling `with_extra_marker("dotenv")` would return
     /// `flask >= 2.0.2 ; extra == "dotenv"`.
     #[must_use]
-    pub fn with_extra_marker(self, extra: &ExtraName) -> Self {
-        let marker = match self.marker {
-            Some(mut marker) => {
-                let extra = MarkerTree::expression(MarkerExpression::Extra {
-                    operator: ExtraOperator::Equal,
-                    name: extra.clone(),
-                });
-                marker.and(extra);
-                marker
-            }
-            None => MarkerTree::expression(MarkerExpression::Extra {
+    pub fn with_extra_marker(mut self, extra: &ExtraName) -> Self {
+        self.marker
+            .and(MarkerTree::expression(MarkerExpression::Extra {
                 operator: ExtraOperator::Equal,
                 name: extra.clone(),
-            }),
-        };
+            }));
 
-        Self {
-            marker: Some(marker),
-            ..self
-        }
+        self
     }
 
     /// Set the source file containing the requirement.
@@ -1053,6 +1027,7 @@ fn parse_pep508_requirement<T: Pep508Url>(
     } else {
         None
     };
+
     // wsp*
     cursor.eat_whitespace();
     if let Some((pos, char)) = cursor.next() {
@@ -1085,7 +1060,7 @@ fn parse_pep508_requirement<T: Pep508Url>(
         name,
         extras,
         version_or_url: requirement_kind,
-        marker,
+        marker: marker.unwrap_or_default(),
         origin: None,
     })
 }
@@ -1222,14 +1197,14 @@ mod tests {
                 .into_iter()
                 .collect(),
             )),
-            marker: Some(MarkerTree::expression(MarkerExpression::Version {
+            marker: MarkerTree::expression(MarkerExpression::Version {
                 key: MarkerValueVersion::PythonVersion,
                 specifier: VersionSpecifier::from_pattern(
                     pep440_rs::Operator::LessThan,
                     "2.7".parse().unwrap(),
                 )
                 .unwrap(),
-            })),
+            }),
             origin: None,
         };
         assert_eq!(requests, expected);
@@ -1455,7 +1430,7 @@ mod tests {
         let expected = Requirement {
             name: PackageName::from_str("pip").unwrap(),
             extras: vec![],
-            marker: None,
+            marker: MarkerTree::TRUE,
             version_or_url: Some(VersionOrUrl::Url(Url::parse(url).unwrap())),
             origin: None,
         };

crates/pep508-rs/src/marker/mod.rs

@@ -21,3 +21,24 @@ pub use tree::{
     MarkerOperator, MarkerTree, MarkerTreeContents, MarkerTreeKind, MarkerValue, MarkerValueString,
     MarkerValueVersion, MarkerWarningKind, StringMarkerTree, StringVersion, VersionMarkerTree,
 };
+
+/// `serde` helpers for [`MarkerTree`].
+pub mod ser {
+    use super::MarkerTree;
+    use serde::Serialize;
+
+    /// A helper for `serde(skip_serializing_if)`.
+    pub fn is_empty(marker: &MarkerTree) -> bool {
+        marker.contents().is_none()
+    }
+
+    /// A helper for `serde(serialize_with)`.
+    ///
+    /// Note this will panic if `marker.contents()` is `None`, and so should be paired with `is_empty`.
+    pub fn serialize<S>(marker: &MarkerTree, s: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        marker.contents().unwrap().serialize(s)
+    }
+}

crates/pep508-rs/src/marker/tree.rs

@@ -564,6 +564,12 @@ impl Display for MarkerExpression {
 #[derive(Clone, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub struct MarkerTree(NodeId);
 
+impl Default for MarkerTree {
+    fn default() -> Self {
+        MarkerTree::TRUE
+    }
+}
+
 impl<'de> Deserialize<'de> for MarkerTree {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where

crates/pep508-rs/src/unnamed.rs

@@ -75,7 +75,7 @@ pub struct UnnamedRequirement<Url: UnnamedRequirementUrl = VerbatimUrl> {
     /// The markers such as `python_version > "3.8"` in
     /// `requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8"`.
     /// Those are a nested and/or tree.
-    pub marker: Option<MarkerTree>,
+    pub marker: MarkerTree,
     /// The source file containing the requirement.
     pub origin: Option<RequirementOrigin>,
 }
@@ -92,11 +92,7 @@ impl<Url: UnnamedRequirementUrl> UnnamedRequirement<Url> {
         env: Option<&MarkerEnvironment>,
         extras: &[ExtraName],
     ) -> bool {
-        if let Some(marker) = &self.marker {
-            marker.evaluate_optional_environment(env, extras)
-        } else {
-            true
-        }
+        self.marker.evaluate_optional_environment(env, extras)
     }
 
     /// Set the source file containing the requirement.
@@ -136,7 +132,7 @@ impl<Url: UnnamedRequirementUrl> Display for UnnamedRequirement<Url> {
                     .join(",")
             )?;
         }
-        if let Some(marker) = self.marker.as_ref().and_then(MarkerTree::contents) {
+        if let Some(marker) = self.marker.contents() {
             write!(f, " ; {marker}")?;
         }
         Ok(())
@@ -207,7 +203,7 @@ fn parse_unnamed_requirement<Url: UnnamedRequirementUrl>(
     Ok(UnnamedRequirement {
         url,
         extras,
-        marker,
+        marker: marker.unwrap_or_default(),
         origin: None,
     })
 }

crates/pypi-types/src/requirement.rs

@@ -3,12 +3,13 @@ use std::path::{Path, PathBuf};
 use std::str::FromStr;
 
 use distribution_filename::DistExtension;
-use serde::Serialize;
 use thiserror::Error;
 use url::Url;
 
 use pep440_rs::VersionSpecifiers;
-use pep508_rs::{MarkerEnvironment, MarkerTree, RequirementOrigin, VerbatimUrl, VersionOrUrl};
+use pep508_rs::{
+    marker, MarkerEnvironment, MarkerTree, RequirementOrigin, VerbatimUrl, VersionOrUrl,
+};
 use uv_fs::PortablePathBuf;
 use uv_git::{GitReference, GitSha, GitUrl};
 use uv_normalize::{ExtraName, PackageName};
@@ -40,40 +41,25 @@ pub struct Requirement {
     #[serde(skip_serializing_if = "Vec::is_empty", default)]
     pub extras: Vec<ExtraName>,
     #[serde(
-        skip_serializing_if = "marker_is_empty",
-        serialize_with = "serialize_marker",
+        skip_serializing_if = "marker::ser::is_empty",
+        serialize_with = "marker::ser::serialize",
         default
     )]
-    pub marker: Option<MarkerTree>,
+    pub marker: MarkerTree,
     #[serde(flatten)]
     pub source: RequirementSource,
     #[serde(skip)]
     pub origin: Option<RequirementOrigin>,
 }
 
-fn marker_is_empty(marker: &Option<MarkerTree>) -> bool {
-    marker.as_ref().and_then(MarkerTree::contents).is_none()
-}
-
-fn serialize_marker<S>(marker: &Option<MarkerTree>, s: S) -> Result<S::Ok, S::Error>
-where
-    S: serde::Serializer,
-{
-    marker.as_ref().unwrap().contents().unwrap().serialize(s)
-}
-
 impl Requirement {
     /// Returns whether the markers apply for the given environment.
     ///
     /// When `env` is `None`, this specifically evaluates all marker
     /// expressions based on the environment to `true`. That is, this provides
     /// environment independent marker evaluation.
     pub fn evaluate_markers(&self, env: Option<&MarkerEnvironment>, extras: &[ExtraName]) -> bool {
-        if let Some(marker) = &self.marker {
-            marker.evaluate_optional_environment(env, extras)
-        } else {
-            true
-        }
+        self.marker.evaluate_optional_environment(env, extras)
     }
 
     /// Returns `true` if the requirement is editable.
@@ -256,7 +242,7 @@ impl Display for Requirement {
                 write!(f, " @ {url}")?;
             }
         }
-        if let Some(marker) = self.marker.as_ref().and_then(MarkerTree::contents) {
+        if let Some(marker) = self.marker.contents() {
             write!(f, " ; {marker}")?;
         }
         Ok(())
@@ -715,7 +701,7 @@ impl TryFrom<RequirementSourceWire> for RequirementSource {
 mod tests {
     use std::path::{Path, PathBuf};
 
-    use pep508_rs::VerbatimUrl;
+    use pep508_rs::{MarkerTree, VerbatimUrl};
 
     use crate::{Requirement, RequirementSource};
 
@@ -724,7 +710,7 @@ mod tests {
         let requirement = Requirement {
             name: "foo".parse().unwrap(),
             extras: vec![],
-            marker: None,
+            marker: MarkerTree::TRUE,
             source: RequirementSource::Registry {
                 specifier: ">1,<2".parse().unwrap(),
                 index: None,
@@ -744,7 +730,7 @@ mod tests {
         let requirement = Requirement {
             name: "foo".parse().unwrap(),
             extras: vec![],
-            marker: None,
+            marker: MarkerTree::TRUE,
             source: RequirementSource::Directory {
                 install_path: PathBuf::from(path),
                 lock_path: PathBuf::from(path),