Use relative paths by default in uv add (#6686)

## Summary

Closes https://github.com/astral-sh/uv/issues/6684.

crates/uv-workspace/src/pyproject.rs

@@ -7,6 +7,7 @@
 //! Then lowers them into a dependency specification.
 
 use std::ops::Deref;
+use std::path::{Path, PathBuf};
 use std::{collections::BTreeMap, mem};
 
 use glob::Pattern;
@@ -16,6 +17,7 @@ use url::Url;
 
 use pep440_rs::VersionSpecifiers;
 use pypi_types::{RequirementSource, SupportedEnvironments, VerbatimParsedUrl};
+use uv_fs::relative_to;
 use uv_git::GitReference;
 use uv_macros::OptionsMetadata;
 use uv_normalize::{ExtraName, PackageName};
@@ -341,6 +343,10 @@ pub enum SourceError {
     UnusedTag(String, String),
     #[error("`{0}` did not resolve to a Git repository, but a Git reference (`--branch {1}`) was provided.")]
     UnusedBranch(String, String),
+    #[error("Failed to resolve absolute path")]
+    Absolute(#[from] std::io::Error),
+    #[error("Path contains invalid characters: `{}`", _0.display())]
+    NonUtf8Path(PathBuf),
 }
 
 impl Source {
@@ -352,6 +358,7 @@ impl Source {
         rev: Option<String>,
         tag: Option<String>,
         branch: Option<String>,
+        root: &Path,
     ) -> Result<Option<Source>, SourceError> {
         // If we resolved to a non-Git source, and the user specified a Git reference, error.
         if !matches!(source, RequirementSource::Git { .. }) {
@@ -386,13 +393,15 @@ impl Source {
 
         let source = match source {
             RequirementSource::Registry { .. } => return Ok(None),
-            RequirementSource::Path { install_path, .. } => Source::Path {
+            RequirementSource::Path { install_path, .. }
+            | RequirementSource::Directory { install_path, .. } => Source::Path {
                 editable,
-                path: install_path.to_string_lossy().into_owned(),
-            },
-            RequirementSource::Directory { install_path, .. } => Source::Path {
-                editable,
-                path: install_path.to_string_lossy().into_owned(),
+                path: relative_to(&install_path, root)
+                    .or_else(|_| std::path::absolute(&install_path))
+                    .map_err(SourceError::Absolute)?
+                    .to_str()
+                    .ok_or_else(|| SourceError::NonUtf8Path(install_path))?
+                    .to_string(),
             },
             RequirementSource::Url {
                 subdirectory, url, ..

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

@@ -338,13 +338,14 @@ pub(crate) async fn add(
             Target::Script(_, _) | Target::Project(_, _) if raw_sources => {
                 (pep508_rs::Requirement::from(requirement), None)
             }
-            Target::Script(_, _) => resolve_requirement(
+            Target::Script(ref script, _) => resolve_requirement(
                 requirement,
                 false,
                 editable,
                 rev.clone(),
                 tag.clone(),
                 branch.clone(),
+                &script.path,
             )?,
             Target::Project(ref project, _) => {
                 let workspace = project
@@ -358,6 +359,7 @@ pub(crate) async fn add(
                     rev.clone(),
                     tag.clone(),
                     branch.clone(),
+                    project.root(),
                 )?
             }
         };
@@ -681,6 +683,7 @@ fn resolve_requirement(
     rev: Option<String>,
     tag: Option<String>,
     branch: Option<String>,
+    root: &Path,
 ) -> Result<(Requirement, Option<Source>), anyhow::Error> {
     let result = Source::from_requirement(
         &requirement.name,
@@ -690,6 +693,7 @@ fn resolve_requirement(
         rev,
         tag,
         branch,
+        root,
     );
 
     let source = match result {

crates/uv/tests/edit.rs

@@ -1626,6 +1626,111 @@ fn add_workspace_editable() -> Result<()> {
     Ok(())
 }
 
+/// Add a path dependency.
+#[test]
+fn add_path() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let workspace = context.temp_dir.child("workspace");
+    workspace.child("pyproject.toml").write_str(indoc! {r#"
+        [project]
+        name = "parent"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+    "#})?;
+
+    let child = workspace.child("child");
+    child.child("pyproject.toml").write_str(indoc! {r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+    "#})?;
+
+    uv_snapshot!(context.filters(), context.add(&["./child"]).current_dir(workspace.path()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtualenv at: .venv
+    Resolved 2 packages in [TIME]
+    Prepared 2 packages in [TIME]
+    Installed 2 packages in [TIME]
+     + child==0.1.0 (from file://[TEMP_DIR]/workspace/child)
+     + parent==0.1.0 (from file://[TEMP_DIR]/workspace)
+    "###);
+
+    let pyproject_toml = fs_err::read_to_string(workspace.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 = [
+            "child",
+        ]
+
+        [tool.uv.sources]
+        child = { path = "child" }
+        "###
+        );
+    });
+
+    // `uv add` implies a full lock and sync, including development dependencies.
+    let lock = fs_err::read_to_string(workspace.join("uv.lock"))?;
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r###"
+        version = 1
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [[package]]
+        name = "child"
+        version = "0.1.0"
+        source = { directory = "child" }
+
+        [[package]]
+        name = "parent"
+        version = "0.1.0"
+        source = { editable = "." }
+        dependencies = [
+            { name = "child" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "child", directory = "child" }]
+        "###
+        );
+    });
+
+    // Install from the lockfile.
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen").current_dir(workspace.path()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Audited 2 packages in [TIME]
+    "###);
+
+    Ok(())
+}
+
 /// Update a requirement, modifying the source and extras.
 #[test]
 #[cfg(feature = "git")]
@@ -3868,7 +3973,7 @@ fn add_git_to_script() -> Result<()> {
     Ok(())
 }
 
-// Revert changes to pyproject.toml if add fails
+/// Revert changes to a `pyproject.toml` the `add` fails.
 #[test]
 fn fail_to_add_revert_project() -> Result<()> {
     let context = TestContext::new("3.12");