feat: respect rust-version when generating lockfile

benches/benchsuite/benches/resolve.rs

@@ -31,7 +31,6 @@ fn do_resolve<'cfg>(config: &'cfg Config, ws_root: &Path) -> ResolveInfo<'cfg> {
     let specs = pkgs.to_package_id_specs(&ws).unwrap();
     let has_dev_units = HasDevUnits::Yes;
     let force_all_targets = ForceAllTargets::No;
-    let max_rust_version = None;
     // Do an initial run to download anything necessary so that it does
     // not confuse criterion's warmup.
     let ws_resolve = cargo::ops::resolve_ws_with_opts(
@@ -42,7 +41,6 @@ fn do_resolve<'cfg>(config: &'cfg Config, ws_root: &Path) -> ResolveInfo<'cfg> {
         &specs,
         has_dev_units,
         force_all_targets,
-        max_rust_version,
     )
     .unwrap();
     ResolveInfo {
@@ -84,7 +82,6 @@ fn resolve_ws(c: &mut Criterion) {
                 force_all_targets,
                 ..
             } = lazy_info.get_or_insert_with(|| do_resolve(&config, &ws_root));
-            let max_rust_version = None;
             b.iter(|| {
                 cargo::ops::resolve_ws_with_opts(
                     ws,
@@ -94,7 +91,6 @@ fn resolve_ws(c: &mut Criterion) {
                     specs,
                     *has_dev_units,
                     *force_all_targets,
-                    max_rust_version,
                 )
                 .unwrap();
             })

crates/cargo-util-schemas/src/manifest.rs

@@ -1417,6 +1417,14 @@ impl std::str::FromStr for RustVersion {
     fn from_str(value: &str) -> Result<Self, Self::Err> {
         let partial = value.parse::<PartialVersion>();
         let partial = partial.map_err(RustVersionErrorKind::PartialVersion)?;
+        partial.try_into()
+    }
+}
+
+impl TryFrom<PartialVersion> for RustVersion {
+    type Error = RustVersionError;
+
+    fn try_from(partial: PartialVersion) -> Result<Self, Self::Error> {
         if partial.pre.is_some() {
             return Err(RustVersionErrorKind::Prerelease.into());
         }

crates/resolver-tests/src/lib.rs

@@ -14,6 +14,7 @@ use std::time::Instant;
 use cargo::core::dependency::DepKind;
 use cargo::core::resolver::{self, ResolveOpts, VersionOrdering, VersionPreferences};
 use cargo::core::Resolve;
+use cargo::core::ResolveVersion;
 use cargo::core::{Dependency, PackageId, Registry, Summary};
 use cargo::core::{GitReference, SourceId};
 use cargo::sources::source::QueryKind;
@@ -174,6 +175,7 @@ pub fn resolve_with_config_raw(
         &[],
         &mut registry,
         &version_prefs,
+        ResolveVersion::with_rust_version(None),
         Some(config),
     );
 

src/cargo/core/compiler/standard_lib.rs

@@ -145,7 +145,6 @@ pub fn resolve_std<'cfg>(
     let cli_features = CliFeatures::from_command_line(
         &features, /*all_features*/ false, /*uses_default_features*/ false,
     )?;
-    let max_rust_version = ws.rust_version();
     let resolve = ops::resolve_ws_with_opts(
         &std_ws,
         target_data,
@@ -154,7 +153,6 @@ pub fn resolve_std<'cfg>(
         &specs,
         HasDevUnits::No,
         crate::core::resolver::features::ForceAllTargets::No,
-        max_rust_version,
     )?;
     Ok((
         resolve.pkg_set,

src/cargo/core/resolver/mod.rs

@@ -118,13 +118,16 @@ mod version_prefs;
 /// * `version_prefs` - this represents a preference for some versions over others,
 ///   based on the lock file or other reasons such as `[patch]`es.
 ///
+/// * `resolve_version` - this controls how the lockfile will be serialized.
+///
 /// * `config` - a location to print warnings and such, or `None` if no warnings
 ///   should be printed
 pub fn resolve(
     summaries: &[(Summary, ResolveOpts)],
     replacements: &[(PackageIdSpec, Dependency)],
     registry: &mut dyn Registry,
     version_prefs: &VersionPreferences,
+    resolve_version: ResolveVersion,
     config: Option<&Config>,
 ) -> CargoResult<Resolve> {
     let _p = profile::start("resolving");
@@ -169,7 +172,7 @@ pub fn resolve(
         cksums,
         BTreeMap::new(),
         Vec::new(),
-        ResolveVersion::default(),
+        resolve_version,
         summaries,
     );
 

src/cargo/core/resolver/resolve.rs

@@ -1,3 +1,6 @@
+use cargo_util_schemas::core::PartialVersion;
+use cargo_util_schemas::manifest::RustVersion;
+
 use super::encode::Metadata;
 use crate::core::dependency::DepKind;
 use crate::core::{Dependency, PackageId, PackageIdSpec, PackageIdSpecQuery, Summary, Target};
@@ -48,7 +51,7 @@ pub struct Resolve {
 
 /// A version to indicate how a `Cargo.lock` should be serialized.
 ///
-/// When creating a new lockfile, the version with `#[default]` is used.
+/// When creating a new lockfile, the version in [`ResolveVersion::default`] is used.
 /// If an old version of lockfile already exists, it will stay as-is.
 ///
 /// It's important that if a new version is added that this is not updated
@@ -64,25 +67,30 @@ pub struct Resolve {
 ///
 /// It's theorized that we can add more here over time to track larger changes
 /// to the `Cargo.lock` format, but we've yet to see how that strategy pans out.
-#[derive(Default, PartialEq, Eq, Clone, Copy, Debug, PartialOrd, Ord)]
+#[derive(PartialEq, Eq, Clone, Copy, Debug, PartialOrd, Ord)]
 pub enum ResolveVersion {
     /// Historical baseline for when this abstraction was added.
     V1,
     /// A more compact format, more amenable to avoiding source-control merge
     /// conflicts. The `dependencies` arrays are compressed and checksums are
-    /// listed inline. Introduced in 2019 in version 1.38. New lockfiles use
-    /// V2 by default from 1.41 to 1.52.
+    /// listed inline.
+    ///
+    /// * Introduced in 2019 in version 1.38.
+    /// * New lockfiles use V2 by default from 1.41 to 1.52.
     V2,
     /// A format that explicitly lists a `version` at the top of the file as
     /// well as changing how git dependencies are encoded. Dependencies with
     /// `branch = "master"` are no longer encoded the same way as those without
-    /// branch specifiers. Introduced in 2020 in version 1.47. New lockfiles use
-    /// V3 by default staring in 1.53.
-    #[default]
+    /// branch specifiers.
+    ///
+    /// * Introduced in 2020 in version 1.47.
+    /// * New lockfiles use V3 by default starting in 1.53.
     V3,
     /// SourceId URL serialization is aware of URL encoding. For example,
     /// `?branch=foo bar` is now encoded as `?branch=foo+bar` and can be decoded
-    /// back and forth correctly. Introduced in 2024 in version 1.77.
+    /// back and forth correctly.
+    ///
+    /// * Introduced in 2024 in version 1.78.
     V4,
     /// Unstable. Will collect a certain amount of changes and then go.
     ///
@@ -91,6 +99,17 @@ pub enum ResolveVersion {
 }
 
 impl ResolveVersion {
+    /// Gets the default lockfile version.
+    ///
+    /// This is intended to be private.
+    /// You shall use [`ResolveVersion::with_rust_version`] always.
+    ///
+    /// Update this and the description of enum variants of [`ResolveVersion`]
+    /// when we're changing the default lockfile version.
+    fn default() -> ResolveVersion {
+        ResolveVersion::V3
+    }
+
     /// The maximum version of lockfile made into the stable channel.
     ///
     /// Any version larger than this needs `-Znext-lockfile-bump` to enable.
@@ -99,6 +118,40 @@ impl ResolveVersion {
     pub fn max_stable() -> ResolveVersion {
         ResolveVersion::V4
     }
+
+    /// Gets the default lockfile version for the given Rust version.
+    pub fn with_rust_version(rust_version: Option<&RustVersion>) -> Self {
+        let Some(rust_version) = rust_version else {
+            return ResolveVersion::default();
+        };
+
+        let rust_1_41 = PartialVersion {
+            major: 1,
+            minor: Some(41),
+            patch: None,
+            pre: None,
+            build: None,
+        }
+        .try_into()
+        .expect("PartialVersion 1.41");
+        let rust_1_53 = PartialVersion {
+            major: 1,
+            minor: Some(53),
+            patch: None,
+            pre: None,
+            build: None,
+        }
+        .try_into()
+        .expect("PartialVersion 1.53");
+
+        if rust_version >= &rust_1_53 {
+            ResolveVersion::V3
+        } else if rust_version >= &rust_1_41 {
+            ResolveVersion::V2
+        } else {
+            ResolveVersion::V1
+        }
+    }
 }
 
 impl Resolve {

src/cargo/ops/cargo_compile/mod.rs

@@ -262,7 +262,6 @@ pub fn create_bcx<'a, 'cfg>(
             HasDevUnits::No
         }
     };
-    let max_rust_version = ws.rust_version();
     let resolve = ops::resolve_ws_with_opts(
         ws,
         &mut target_data,
@@ -271,7 +270,6 @@ pub fn create_bcx<'a, 'cfg>(
         &specs,
         has_dev_units,
         crate::core::resolver::features::ForceAllTargets::No,
-        max_rust_version,
     )?;
     let WorkspaceResolve {
         mut pkg_set,

src/cargo/ops/cargo_generate_lockfile.rs

@@ -26,7 +26,6 @@ pub struct UpdateOptions<'a> {
 
 pub fn generate_lockfile(ws: &Workspace<'_>) -> CargoResult<()> {
     let mut registry = PackageRegistry::new(ws.config())?;
-    let max_rust_version = ws.rust_version();
     let mut resolve = ops::resolve_with_previous(
         &mut registry,
         ws,
@@ -36,7 +35,6 @@ pub fn generate_lockfile(ws: &Workspace<'_>) -> CargoResult<()> {
         None,
         &[],
         true,
-        max_rust_version,
     )?;
     ops::write_pkg_lockfile(ws, &mut resolve)?;
     Ok(())
@@ -57,8 +55,6 @@ pub fn update_lockfile(ws: &Workspace<'_>, opts: &UpdateOptions<'_>) -> CargoRes
         .config()
         .acquire_package_cache_lock(CacheLockMode::DownloadExclusive)?;
 
-    let max_rust_version = ws.rust_version();
-
     let previous_resolve = match ops::load_pkg_lockfile(ws)? {
         Some(resolve) => resolve,
         None => {
@@ -78,7 +74,6 @@ pub fn update_lockfile(ws: &Workspace<'_>, opts: &UpdateOptions<'_>) -> CargoRes
                         None,
                         &[],
                         true,
-                        max_rust_version,
                     )?
                 }
             }
@@ -157,7 +152,6 @@ pub fn update_lockfile(ws: &Workspace<'_>, opts: &UpdateOptions<'_>) -> CargoRes
         Some(&to_avoid),
         &[],
         true,
-        max_rust_version,
     )?;
 
     // Summarize what is changing for the user.

src/cargo/ops/cargo_output_metadata.rs

@@ -140,8 +140,6 @@ fn build_resolve_graph(
         crate::core::resolver::features::ForceAllTargets::No
     };
 
-    let max_rust_version = ws.rust_version();
-
     // Note that even with --filter-platform we end up downloading host dependencies as well,
     // as that is the behavior of download_accessible.
     let ws_resolve = ops::resolve_ws_with_opts(
@@ -152,7 +150,6 @@ fn build_resolve_graph(
         &specs,
         HasDevUnits::Yes,
         force_all,
-        max_rust_version,
     )?;
 
     let package_map: BTreeMap<PackageId, Package> = ws_resolve

src/cargo/ops/cargo_package.rs

@@ -461,8 +461,6 @@ fn build_lock(ws: &Workspace<'_>, orig_pkg: &Package) -> CargoResult<String> {
         to_real_manifest(toml_manifest, false, source_id, package_root, config)?;
     let new_pkg = Package::new(manifest, orig_pkg.manifest_path());
 
-    let max_rust_version = new_pkg.rust_version().cloned();
-
     // Regenerate Cargo.lock using the old one as a guide.
     let tmp_ws = Workspace::ephemeral(new_pkg, ws.config(), None, true)?;
     let mut tmp_reg = PackageRegistry::new(ws.config())?;
@@ -475,7 +473,6 @@ fn build_lock(ws: &Workspace<'_>, orig_pkg: &Package) -> CargoResult<String> {
         None,
         &[],
         true,
-        max_rust_version.as_ref(),
     )?;
     let pkg_set = ops::get_resolved_packages(&new_resolve, tmp_reg)?;
 

src/cargo/ops/fix.rs

@@ -245,8 +245,6 @@ fn check_resolver_change(ws: &Workspace<'_>, opts: &FixOptions) -> CargoResult<(
     let mut target_data =
         RustcTargetData::new(ws, &opts.compile_opts.build_config.requested_kinds)?;
     let mut resolve_differences = |has_dev_units| -> CargoResult<(WorkspaceResolve<'_>, DiffMap)> {
-        let max_rust_version = ws.rust_version();
-
         let ws_resolve = ops::resolve_ws_with_opts(
             ws,
             &mut target_data,
@@ -255,7 +253,6 @@ fn check_resolver_change(ws: &Workspace<'_>, opts: &FixOptions) -> CargoResult<(
             &specs,
             has_dev_units,
             crate::core::resolver::features::ForceAllTargets::No,
-            max_rust_version,
         )?;
 
         let feature_opts = FeatureOpts::new_behavior(ResolveBehavior::V2, has_dev_units);

src/cargo/ops/lockfile.rs

@@ -64,9 +64,10 @@ pub fn write_pkg_lockfile(ws: &Workspace<'_>, resolve: &mut Resolve) -> CargoRes
     // out lock file updates as they're otherwise already updated, and changes
     // which don't touch dependencies won't seemingly spuriously update the lock
     // file.
-    let default_version = ResolveVersion::default();
+    let default_version = ResolveVersion::with_rust_version(ws.rust_version());
     let current_version = resolve.version();
     let next_lockfile_bump = ws.config().cli_unstable().next_lockfile_bump;
+    tracing::debug!("lockfile - current: {current_version:?}, default: {default_version:?}");
 
     if current_version < default_version {
         resolve.set_version(default_version);