Reject self-dependencies in uv add (#7766)

## Summary

However, adding a recursive extra _is_ allowed.

Closes #7731.

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

@@ -338,6 +338,27 @@ pub(crate) async fn add(
         requirements
     };
 
+    // If any of the requirements are self-dependencies, bail.
+    if matches!(
+        dependency_type,
+        DependencyType::Production | DependencyType::Dev
+    ) {
+        if let Target::Project(project, _) = &target {
+            if let Some(project_name) = project.project_name() {
+                for requirement in &requirements {
+                    if requirement.name == *project_name {
+                        bail!(
+                            "Requirement name `{}` matches project name `{}`, but self-dependencies are not permitted. If your project name (`{}`) is shadowing that of a third-party dependency, consider renaming the project.",
+                            requirement.name.cyan(),
+                            project_name.cyan(),
+                            project_name.cyan(),
+                        );
+                    }
+                }
+            }
+        }
+    }
+
     // Add the requirements to the `pyproject.toml` or script.
     let mut toml = match &target {
         Target::Script(script, _) => {

crates/uv/tests/edit.rs

@@ -4806,6 +4806,7 @@ fn update_offset() -> Result<()> {
         "###
         );
     });
+
     Ok(())
 }
 
@@ -4865,3 +4866,92 @@ fn add_shadowed_name() -> Result<()> {
 
     Ok(())
 }
+
+/// Accidentally add a dependency on the project itself.
+#[test]
+fn add_self() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "anyio"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+    "#})?;
+
+    uv_snapshot!(context.filters(), context.add().arg("anyio==3.7.0"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Requirement name `anyio` matches project name `anyio`, but self-dependencies are not permitted. If your project name (`anyio`) is shadowing that of a third-party dependency, consider renaming the project.
+    "###);
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "anyio"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [project.optional-dependencies]
+        types = ["typing-extensions>=4"]
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+    "#})?;
+
+    // However, recursive extras are fine.
+    uv_snapshot!(context.filters(), context.add().arg("anyio[types]").arg("--optional").arg("all"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 2 packages in [TIME]
+    Installed 2 packages in [TIME]
+     + anyio==0.1.0 (from file://[TEMP_DIR]/)
+     + typing-extensions==4.10.0
+    "###);
+
+    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 = "anyio"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [project.optional-dependencies]
+        types = ["typing-extensions>=4"]
+        all = [
+            "anyio[types]",
+        ]
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+
+        [tool.uv.sources]
+        anyio = { workspace = true }
+        "###
+        );
+    });
+
+    Ok(())
+}