Avoid erroring on omitted wheel-only packages in `pylock.toml` (#13132)

## Summary

Closes https://github.com/astral-sh/uv/issues/13127.

crates/uv-resolver/src/lock/export/pylock_toml.rs

@@ -62,6 +62,8 @@ pub enum PylockTomlError {
         "Package `{0}` must include one of: `wheels`, `directory`, `archive`, `sdist`, or `vcs`"
     )]
     MissingSource(PackageName),
+    #[error("Package `{0}` does not include a compatible wheel for the current platform")]
+    MissingWheel(PackageName),
     #[error("`packages.wheel` entry for `{0}` must have a `path` or `url`")]
     WheelMissingPathUrl(PackageName),
     #[error("`packages.sdist` entry for `{0}` must have a `path` or `url`")]
@@ -863,6 +865,11 @@ impl<'lock> PylockToml {
         let root = graph.add_node(Node::Root);
 
         for package in self.packages {
+            // Omit packages that aren't relevant to the current environment.
+            if !package.marker.evaluate(markers, &[]) {
+                continue;
+            }
+
             match (
                 package.wheels.is_some(),
                 package.sdist.is_some(),
@@ -901,12 +908,12 @@ impl<'lock> PylockToml {
                 (_, _, _, true, true) => {
                     return Err(PylockTomlError::VcsWithArchive(package.name.clone()));
                 }
+                (false, false, false, false, false) => {
+                    return Err(PylockTomlError::MissingSource(package.name.clone()));
+                }
                 _ => {}
             }
 
-            // Omit packages that aren't relevant to the current environment.
-            let install = package.marker.evaluate(markers, &[]);
-
             // Search for a matching wheel.
             let dist = if let Some(best_wheel) = package.find_best_wheel(tags) {
                 let hashes = HashDigests::from(best_wheel.hashes.clone());
@@ -926,7 +933,7 @@ impl<'lock> PylockToml {
                 Node::Dist {
                     dist,
                     hashes,
-                    install,
+                    install: true,
                 }
             } else if let Some(sdist) = package.sdist.as_ref() {
                 let hashes = HashDigests::from(sdist.hashes.clone());
@@ -943,7 +950,7 @@ impl<'lock> PylockToml {
                 Node::Dist {
                     dist,
                     hashes,
-                    install,
+                    install: true,
                 }
             } else if let Some(sdist) = package.directory.as_ref() {
                 let hashes = HashDigests::empty();
@@ -957,7 +964,7 @@ impl<'lock> PylockToml {
                 Node::Dist {
                     dist,
                     hashes,
-                    install,
+                    install: true,
                 }
             } else if let Some(sdist) = package.vcs.as_ref() {
                 let hashes = HashDigests::empty();
@@ -971,7 +978,7 @@ impl<'lock> PylockToml {
                 Node::Dist {
                     dist,
                     hashes,
-                    install,
+                    install: true,
                 }
             } else if let Some(dist) = package.archive.as_ref() {
                 let hashes = HashDigests::from(dist.hashes.clone());
@@ -983,10 +990,16 @@ impl<'lock> PylockToml {
                 Node::Dist {
                     dist,
                     hashes,
-                    install,
+                    install: true,
                 }
             } else {
-                return Err(PylockTomlError::MissingSource(package.name.clone()));
+                // This is only reachable if the package contains a `wheels` entry (and nothing
+                // else), but there are no wheels available for the current environment. (If the
+                // package doesn't contain _any_ of `wheels`, `sdist`, etc., then we error in the
+                // match above.)
+                //
+                // TODO(charlie): Include a hint, like in `uv.lock`.
+                return Err(PylockTomlError::MissingWheel(package.name.clone()));
             };
 
             let index = graph.add_node(dist);

crates/uv/tests/it/pip_sync.rs

@@ -5822,3 +5822,78 @@ fn pep_751() -> Result<()> {
 
     Ok(())
 }
+
+/// Avoid erroring for packages that only include wheels, and _don't_ include a wheel for the
+/// current platform, but are omitted by markers anyway.
+///
+/// See: <https://github.com/astral-sh/uv/issues/13127>
+#[test]
+fn pep_751_wheel_only() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12.0"
+        dependencies = ["torch"]
+        "#,
+    )?;
+
+    context
+        .export()
+        .arg("-o")
+        .arg("pylock.toml")
+        .assert()
+        .success();
+
+    // If there's no compatible wheel for a package we _don't_ need to install (e.g., anything
+    // CUDA-related), succeed.
+    uv_snapshot!(context.filters(), context.pip_sync()
+        .arg("--preview")
+        .arg("pylock.toml")
+        .arg("--dry-run")
+        .arg("--python-platform")
+        .arg("macos"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Would download 9 packages
+    Would install 9 packages
+     + filelock==3.13.1
+     + fsspec==2024.3.1
+     + jinja2==3.1.3
+     + markupsafe==2.1.5
+     + mpmath==1.3.0
+     + networkx==3.2.1
+     + sympy==1.12
+     + torch==2.2.1
+     + typing-extensions==4.10.0
+    "
+    );
+
+    // However, if there's no compatible wheel for a package that we _do_ need to install, we should
+    // error
+    uv_snapshot!(context.filters(), context.pip_sync()
+        .arg("--preview")
+        .arg("pylock.toml")
+        .arg("--dry-run")
+        .arg("--python-platform")
+        .arg("macos")
+        .arg("--python-version")
+        .arg("3.8"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Package `torch` does not include a compatible wheel for the current platform
+    "
+    );
+
+    Ok(())
+}