Re-sync editables on-change (#1959)

## Summary

Like #1955, but for `pip sync`.

Closes https://github.com/astral-sh/uv/issues/1957.

crates/uv-installer/src/plan.rs

@@ -444,16 +444,16 @@ fn not_modified_cache(cache_entry: &CacheEntry, artifact: &Path) -> Result<bool,
 /// not-modified based on the modification time of the installed distribution.
 fn not_modified_install(dist: &InstalledDirectUrlDist, artifact: &Path) -> Result<bool, io::Error> {
     // Determine the modification time of the installed distribution.
-    let dist_metadata = fs_err::metadata(&dist.path)?;
+    let dist_metadata = fs_err::metadata(dist.path.join("METADATA"))?;
     let dist_timestamp = Timestamp::from_metadata(&dist_metadata);
 
     // Determine the modification time of the wheel.
-    if let Some(artifact_timestamp) = ArchiveTimestamp::from_path(artifact)? {
+    let Some(artifact_timestamp) = ArchiveTimestamp::from_path(artifact)? else {
-        Ok(dist_timestamp >= artifact_timestamp.timestamp())
-    } else {
         // The artifact doesn't exist, so it's not fresh.
-        Ok(false)
+        return Ok(false);
-    }
+    };
+
+    Ok(dist_timestamp >= artifact_timestamp.timestamp())
 }
 
 #[derive(Debug, Default)]

crates/uv-resolver/src/resolver/urls.rs

@@ -42,29 +42,27 @@ impl Urls {
         }
 
         // Add any editable requirements. If there are any conflicts, return an error.
-        for (editable_requirement, metadata) in &manifest.editables {
+        for (requirement, metadata) in &manifest.editables {
-            if let Some(previous) =
+            if let Some(previous) = urls.insert(metadata.name.clone(), requirement.url.clone()) {
-                urls.insert(metadata.name.clone(), editable_requirement.url.clone())
-            {
                 if cache_key::CanonicalUrl::new(previous.raw())
-                    != cache_key::CanonicalUrl::new(editable_requirement.raw())
+                    != cache_key::CanonicalUrl::new(requirement.raw())
                 {
                     return Err(ResolveError::ConflictingUrlsDirect(
                         metadata.name.clone(),
                         previous.verbatim().to_string(),
-                        editable_requirement.url.verbatim().to_string(),
+                        requirement.verbatim().to_string(),
                     ));
                 }
             }
 
-            for req in &metadata.requires_dist {
+            for requirement in &metadata.requires_dist {
-                if let Some(pep508_rs::VersionOrUrl::Url(url)) = &req.version_or_url {
+                if let Some(pep508_rs::VersionOrUrl::Url(url)) = &requirement.version_or_url {
-                    if let Some(previous) = urls.insert(req.name.clone(), url.clone()) {
+                    if let Some(previous) = urls.insert(requirement.name.clone(), url.clone()) {
                         if cache_key::CanonicalUrl::new(previous.raw())
                             != cache_key::CanonicalUrl::new(url.raw())
                         {
                             return Err(ResolveError::ConflictingUrlsDirect(
-                                req.name.clone(),
+                                requirement.name.clone(),
                                 previous.verbatim().to_string(),
                                 url.verbatim().to_string(),
                             ));

crates/uv/src/commands/pip_install.rs

@@ -496,14 +496,16 @@ async fn install(
 ) -> Result<(), Error> {
     let start = std::time::Instant::now();
 
-    // Partition into those that should be linked from the cache (`local`), those that need to be
-    // downloaded (`remote`), and those that should be removed (`extraneous`).
     let requirements = resolution.requirements();
+
+    // Map the built editables to their resolved form.
     let editables = built_editables
         .into_iter()
         .map(ResolvedEditable::Built)
         .collect::<Vec<_>>();
 
+    // Partition into those that should be linked from the cache (`local`), those that need to be
+    // downloaded (`remote`), and those that should be removed (`extraneous`).
     let Plan {
         local,
         remote,

crates/uv/src/commands/pip_sync.rs

@@ -5,13 +5,15 @@ use itertools::Itertools;
 use owo_colors::OwoColorize;
 use tracing::debug;
 
-use distribution_types::{IndexLocations, InstalledMetadata, LocalDist, LocalEditable, Name};
+use distribution_types::{
+    IndexLocations, InstalledDist, InstalledMetadata, LocalDist, LocalEditable, Name,
+};
 use install_wheel_rs::linker::LinkMode;
 use platform_host::Platform;
 use platform_tags::Tags;
 use pypi_types::Yanked;
 use requirements_txt::EditableRequirement;
-use uv_cache::Cache;
+use uv_cache::{ArchiveTimestamp, Cache};
 use uv_client::{Connectivity, FlatIndex, FlatIndexClient, RegistryClient, RegistryClientBuilder};
 use uv_dispatch::BuildDispatch;
 use uv_fs::Normalized;
@@ -392,6 +394,18 @@ async fn resolve_editables(
     build_dispatch: &BuildDispatch<'_>,
     mut printer: Printer,
 ) -> Result<ResolvedEditables> {
+    /// Returns `true` if the installed distribution is up-to-date.
+    fn not_modified(editable: &EditableRequirement, installed: &InstalledDist) -> bool {
+        let Ok(Some(installed_at)) = ArchiveTimestamp::from_path(installed.path().join("METADATA"))
+        else {
+            return false;
+        };
+        let Ok(Some(modified_at)) = ArchiveTimestamp::from_path(&editable.path) else {
+            return false;
+        };
+        installed_at > modified_at
+    }
+
     // Partition the editables into those that are already installed, and those that must be built.
     let mut installed = Vec::with_capacity(editables.len());
     let mut uninstalled = Vec::with_capacity(editables.len());
@@ -401,7 +415,13 @@ async fn resolve_editables(
                 let existing = site_packages.get_editables(editable.raw());
                 match existing.as_slice() {
                     [] => uninstalled.push(editable),
-                    [dist] => installed.push((*dist).clone()),
+                    [dist] => {
+                        if not_modified(&editable, dist) {
+                            installed.push((*dist).clone());
+                        } else {
+                            uninstalled.push(editable);
+                        }
+                    }
                     _ => {
                         uninstalled.push(editable);
                     }
@@ -414,11 +434,15 @@ async fn resolve_editables(
                 let existing = site_packages.get_editables(editable.raw());
                 match existing.as_slice() {
                     [] => uninstalled.push(editable),
-                    [dist] => {
+                    [dist] if not_modified(&editable, dist) => {
                         if packages.contains(dist.name()) {
                             uninstalled.push(editable);
                         } else {
-                            installed.push((*dist).clone());
+                            if not_modified(&editable, dist) {
+                                installed.push((*dist).clone());
+                            } else {
+                                uninstalled.push(editable);
+                            }
                         }
                     }
                     _ => {

crates/uv/tests/pip_sync.rs

@@ -2799,3 +2799,86 @@ fn pip_entrypoints() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn invalidate_on_change() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    // Create an editable package.
+    let editable_dir = assert_fs::TempDir::new()?;
+    let pyproject_toml = editable_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"[project]
+name = "example"
+version = "0.0.0"
+dependencies = [
+  "anyio==4.0.0"
+]
+requires-python = ">=3.8"
+"#,
+    )?;
+
+    // Write to a requirements file.
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str(&format!("-e {}", editable_dir.path().display()))?;
+
+    let filters = [(r"\(from file://.*\)", "(from [WORKSPACE_DIR])")]
+        .into_iter()
+        .chain(INSTA_FILTERS.to_vec())
+        .collect::<Vec<_>>();
+
+    uv_snapshot!(filters, command(&context)
+        .arg("requirements.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Built 1 editable in [TIME]
+    Installed 1 package in [TIME]
+     + example==0.0.0 (from [WORKSPACE_DIR])
+    "###
+    );
+
+    // Re-installing should be a no-op.
+    uv_snapshot!(filters, command(&context)
+        .arg("requirements.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Audited 1 package in [TIME]
+    "###
+    );
+
+    // Modify the editable package.
+    pyproject_toml.write_str(
+        r#"[project]
+name = "example"
+version = "0.0.0"
+dependencies = [
+  "anyio==3.7.1"
+]
+requires-python = ">=3.8"
+"#,
+    )?;
+
+    // Re-installing should update the package.
+    uv_snapshot!(filters, command(&context)
+        .arg("requirements.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Built 1 editable in [TIME]
+    Uninstalled 1 package in [TIME]
+    Installed 1 package in [TIME]
+     - example==0.0.0 (from [WORKSPACE_DIR])
+     + example==0.0.0 (from [WORKSPACE_DIR])
+    "###
+    );
+
+    Ok(())
+}