Filter irrelevant requirements from source annotations (#3479)

## Summary

If a requirement is omitted due to a marker expression, we shouldn't
include it as the "source" of a package in the output.

For example, if your constraints include `pathspec ; python_version <
'3.12'`, and you're on Python 3.12, we should _not_ include the
constraint file as a "source" in the output annotations.

crates/uv/src/commands/pip_compile.rs

@@ -357,7 +357,10 @@ pub(crate) async fn pip_compile(
     // Generate a map from requirement to originating source file.
     let mut sources = SourceAnnotations::default();
 
-    for requirement in &requirements {
+    for requirement in requirements
+        .iter()
+        .filter(|requirement| requirement.evaluate_markers(&markers, &[]))
+    {
         if let Some(path) = &requirement.path {
             if path.ends_with("pyproject.toml") {
                 sources.add(
@@ -376,7 +379,10 @@ pub(crate) async fn pip_compile(
         }
     }
 
-    for requirement in &constraints {
+    for requirement in constraints
+        .iter()
+        .filter(|requirement| requirement.evaluate_markers(&markers, &[]))
+    {
         if let Some(path) = &requirement.path {
             sources.add(
                 &requirement.name,
@@ -385,7 +391,10 @@ pub(crate) async fn pip_compile(
         }
     }
 
-    for requirement in &overrides {
+    for requirement in overrides
+        .iter()
+        .filter(|requirement| requirement.evaluate_markers(&markers, &[]))
+    {
         if let Some(path) = &requirement.path {
             sources.add(&requirement.name, SourceAnnotation::Override(path.clone()));
         }

crates/uv/tests/pip_compile.rs

@@ -1034,6 +1034,41 @@ fn compile_python_dev_version() -> Result<()> {
     Ok(())
 }
 
+/// Omit the constraint annotation (e.g., `# from -c constraints.txt`) when the constraint is not
+/// applicable due to a marker expression.
+#[test]
+fn omit_non_matching_annotation() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("anyio")?;
+
+    let constraints_txt = context.temp_dir.child("constraints.txt");
+    constraints_txt.write_str("idna <3.7; python_version < '3.7'")?;
+
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("-c")
+            .arg("constraints.txt"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] --exclude-newer 2024-03-25T00:00:00Z requirements.in -c constraints.txt
+    anyio==4.3.0
+        # via -r requirements.in
+    idna==3.6
+        # via anyio
+    sniffio==1.3.1
+        # via anyio
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    "###
+    );
+
+    Ok(())
+}
+
 /// Test that we select the last 3.8 compatible numpy version instead of trying to compile an
 /// incompatible sdist <https://github.com/astral-sh/uv/issues/388>
 #[test]