Revert uv.lock changes when uv add fails (#9030)

## Summary

If a `uv add` fails at the sync stage, we need to clean up the changes
to the `uv.lock`, since it might've been edited during in the lock stage
(which, by necessity, succeeded). As-is, we revert the `pyproject.toml`
but not the `uv.lock`, so the two are out-of-sync.

Closes #9028.
Closes #7992.

crates/uv/src/commands/project/add.rs

@@ -1,5 +1,6 @@
 use std::collections::hash_map::Entry;
 use std::fmt::Write;
+use std::io;
 use std::path::{Path, PathBuf};
 
 use anyhow::{bail, Context, Result};
@@ -44,7 +45,7 @@ use crate::commands::pip::loggers::{
 use crate::commands::pip::operations::Modifications;
 use crate::commands::project::lock::LockMode;
 use crate::commands::project::{
-    init_script_python_requirement, validate_script_requires_python, ProjectError,
+    init_script_python_requirement, lock, validate_script_requires_python, ProjectError,
     ProjectInterpreter, ScriptPython,
 };
 use crate::commands::reporters::{PythonDownloadReporter, ResolverReporter};
@@ -618,8 +619,10 @@ pub(crate) async fn add(
     }
 
     // Store the content prior to any modifications.
-    let existing = project.pyproject_toml().as_ref().to_vec();
-    let root = project.root().to_path_buf();
+    let project_root = project.root().to_path_buf();
+    let workspace_root = project.workspace().install_path().clone();
+    let existing_pyproject_toml = project.pyproject_toml().as_ref().to_vec();
+    let existing_uv_lock = lock::read_bytes(project.workspace()).await?;
 
     // Update the `pypackage.toml` in-memory.
     let project = project
@@ -628,12 +631,18 @@ pub(crate) async fn add(
 
     // Set the Ctrl-C handler to revert changes on exit.
     let _ = ctrlc::set_handler({
-        let root = root.clone();
-        let existing = existing.clone();
+        let project_root = project_root.clone();
+        let workspace_root = workspace_root.clone();
+        let existing_pyproject_toml = existing_pyproject_toml.clone();
+        let existing_uv_lock = existing_uv_lock.clone();
         move || {
-            // Revert the changes to the `pyproject.toml`, if necessary.
             if modified {
-                let _ = fs_err::write(root.join("pyproject.toml"), &existing);
+                let _ = revert(
+                    &project_root,
+                    &workspace_root,
+                    &existing_pyproject_toml,
+                    existing_uv_lock.as_deref(),
+                );
             }
 
             #[allow(clippy::exit, clippy::cast_possible_wrap)]
@@ -667,9 +676,13 @@ pub(crate) async fn add(
     {
         Ok(()) => Ok(ExitStatus::Success),
         Err(err) => {
-            // Revert the changes to the `pyproject.toml`, if necessary.
             if modified {
-                fs_err::write(root.join("pyproject.toml"), &existing)?;
+                let _ = revert(
+                    &project_root,
+                    &workspace_root,
+                    &existing_pyproject_toml,
+                    existing_uv_lock.as_deref(),
+                );
             }
 
             match err {
@@ -703,13 +716,7 @@ pub(crate) async fn add(
                     diagnostics::build(dist, err);
                     Ok(ExitStatus::Failure)
                 }
-                err => {
-                    // Revert the changes to the `pyproject.toml`, if necessary.
-                    if modified {
-                        fs_err::write(root.join("pyproject.toml"), &existing)?;
-                    }
-                    Err(err.into())
-                }
+                err => Err(err.into()),
             }
         }
     }
@@ -943,6 +950,25 @@ async fn lock_and_sync(
     Ok(())
 }
 
+/// Revert the changes to the `pyproject.toml` and `uv.lock`, if necessary.
+fn revert(
+    project_root: &Path,
+    workspace_root: &Path,
+    pyproject_toml: &[u8],
+    uv_lock: Option<&[u8]>,
+) -> Result<(), io::Error> {
+    debug!("Reverting changes to `pyproject.toml`");
+    let () = fs_err::write(project_root.join("pyproject.toml"), pyproject_toml)?;
+    if let Some(uv_lock) = uv_lock.as_ref() {
+        debug!("Reverting changes to `uv.lock`");
+        let () = fs_err::write(workspace_root.join("uv.lock"), uv_lock)?;
+    } else {
+        debug!("Removing `uv.lock`");
+        let () = fs_err::remove_file(workspace_root.join("uv.lock"))?;
+    }
+    Ok(())
+}
+
 /// Augment a user-provided requirement by attaching any specification data that was provided
 /// separately from the requirement itself (e.g., `--branch main`).
 fn augment_requirement(

crates/uv/src/commands/project/lock.rs

@@ -1009,6 +1009,17 @@ pub(crate) async fn read(workspace: &Workspace) -> Result<Option<Lock>, ProjectE
     }
 }
 
+/// Read the lockfile from the workspace as bytes.
+///
+/// Returns `Ok(None)` if the lockfile does not exist.
+pub(crate) async fn read_bytes(workspace: &Workspace) -> Result<Option<Vec<u8>>, ProjectError> {
+    match fs_err::tokio::read(&workspace.install_path().join("uv.lock")).await {
+        Ok(encoded) => Ok(Some(encoded)),
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(None),
+        Err(err) => Err(err.into()),
+    }
+}
+
 /// Reports on the versions that were upgraded in the new lockfile.
 ///
 /// Returns `true` if any upgrades were reported.

crates/uv/tests/it/edit.rs

@@ -5506,76 +5506,206 @@ fn add_git_to_script() -> Result<()> {
     Ok(())
 }
 
-/// Revert changes to a `pyproject.toml` the `add` fails.
+/// Revert changes to the `pyproject.toml` and `uv.lock` when the `add` operation fails.
 #[test]
 fn fail_to_add_revert_project() -> Result<()> {
     let context = TestContext::new("3.12");
 
-    let pyproject_toml = context.temp_dir.child("pyproject.toml");
-    pyproject_toml.write_str(indoc! {r#"
+    context
+        .temp_dir
+        .child("pyproject.toml")
+        .write_str(indoc! {r#"
         [project]
-        name = "project"
+        name = "parent"
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+    "#})?;
+
+    // Add a dependency on a package that declares static metadata (so can always resolve), but
+    // can't be installed.
+    let pyproject_toml = context.temp_dir.child("child/pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["iniconfig"]
 
         [build-system]
         requires = ["setuptools>=42"]
         build-backend = "setuptools.build_meta"
     "#})?;
+    context
+        .temp_dir
+        .child("src")
+        .child("child")
+        .child("__init__.py")
+        .touch()?;
+    context
+        .temp_dir
+        .child("child")
+        .child("setup.py")
+        .write_str("1/0")?;
 
-    // Adding `pytorch==1.0.2` should produce an error
     let filters = std::iter::once((r"exit code: 1", "exit status: 1"))
         .chain(context.filters())
         .collect::<Vec<_>>();
-    uv_snapshot!(filters, context.add().arg("pytorch==1.0.2"), @r###"
+    uv_snapshot!(filters, context.add().arg("./child"), @r###"
     success: false
     exit_code: 2
     ----- stdout -----
 
     ----- stderr -----
-    Resolved 2 packages in [TIME]
+    Resolved 3 packages in [TIME]
     error: Failed to prepare distributions
-      Caused by: Failed to download and build `pytorch==1.0.2`
-      Caused by: Build backend failed to build wheel through `build_wheel` (exit status: 1)
+      Caused by: Failed to build `child @ file://[TEMP_DIR]/child`
+      Caused by: Build backend failed to determine requirements with `build_wheel()` (exit status: 1)
 
     [stderr]
     Traceback (most recent call last):
-      File "<string>", line 11, in <module>
-      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 410, in build_wheel
-        return self._build_with_temp_dir(
-               ^^^^^^^^^^^^^^^^^^^^^^^^^^
-      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 395, in _build_with_temp_dir
+      File "<string>", line 14, in <module>
+      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 325, in get_requires_for_build_wheel
+        return self._get_build_requires(config_settings, requirements=['wheel'])
+               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 295, in _get_build_requires
         self.run_setup()
-      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 487, in run_setup
-        super().run_setup(setup_script=setup_script)
       File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 311, in run_setup
         exec(code, locals())
-      File "<string>", line 15, in <module>
-    Exception: You tried to install "pytorch". The package named for PyTorch is "torch"
-
+      File "<string>", line 1, in <module>
+    ZeroDivisionError: division by zero
     "###);
 
-    let pyproject_toml = context.read("pyproject.toml");
+    let pyproject_toml = fs_err::read_to_string(context.temp_dir.join("pyproject.toml"))?;
 
     insta::with_settings!({
         filters => context.filters(),
     }, {
         assert_snapshot!(
             pyproject_toml, @r###"
         [project]
-        name = "project"
+        name = "parent"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+        "###
+        );
+    });
+
+    // The lockfile should not exist, even though resolution succeeded.
+    assert!(!context.temp_dir.join("uv.lock").exists());
+
+    Ok(())
+}
+
+/// Revert changes to the `pyproject.toml` and `uv.lock` when the `add` operation fails.
+///
+/// In this case, the project has an existing lockfile.
+#[test]
+fn fail_to_edit_revert_project() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    context
+        .temp_dir
+        .child("pyproject.toml")
+        .write_str(indoc! {r#"
+        [project]
+        name = "parent"
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+    "#})?;
+
+    uv_snapshot!(context.filters(), context.add().arg("iniconfig"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.0.0
+    "###);
+
+    let before = fs_err::read_to_string(context.temp_dir.join("uv.lock"))?;
+
+    // Add a dependency on a package that declares static metadata (so can always resolve), but
+    // can't be installed.
+    let pyproject_toml = context.temp_dir.child("child/pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["iniconfig"]
 
         [build-system]
         requires = ["setuptools>=42"]
         build-backend = "setuptools.build_meta"
+    "#})?;
+    context
+        .temp_dir
+        .child("src")
+        .child("child")
+        .child("__init__.py")
+        .touch()?;
+    context
+        .temp_dir
+        .child("child")
+        .child("setup.py")
+        .write_str("1/0")?;
+
+    let filters = std::iter::once((r"exit code: 1", "exit status: 1"))
+        .chain(context.filters())
+        .collect::<Vec<_>>();
+    uv_snapshot!(filters, context.add().arg("./child"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    error: Failed to prepare distributions
+      Caused by: Failed to build `child @ file://[TEMP_DIR]/child`
+      Caused by: Build backend failed to determine requirements with `build_wheel()` (exit status: 1)
+
+    [stderr]
+    Traceback (most recent call last):
+      File "<string>", line 14, in <module>
+      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 325, in get_requires_for_build_wheel
+        return self._get_build_requires(config_settings, requirements=['wheel'])
+               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 295, in _get_build_requires
+        self.run_setup()
+      File "[CACHE_DIR]/builds-v0/[TMP]/build_meta.py", line 311, in run_setup
+        exec(code, locals())
+      File "<string>", line 1, in <module>
+    ZeroDivisionError: division by zero
+    "###);
+
+    let pyproject_toml = fs_err::read_to_string(context.temp_dir.join("pyproject.toml"))?;
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            pyproject_toml, @r###"
+        [project]
+        name = "parent"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = [
+            "iniconfig>=2.0.0",
+        ]
         "###
         );
     });
 
+    // The lockfile should exist, but be unchanged.
+    let after = fs_err::read_to_string(context.temp_dir.join("uv.lock"))?;
+    assert_eq!(before, after);
+
     Ok(())
 }