Require disambiguated relative paths for --index

crates/uv-cli/src/lib.rs

@@ -5068,6 +5068,9 @@ pub struct IndexArgs {
     /// All indexes provided via this flag take priority over the index specified by
     /// `--default-index` (which defaults to PyPI). When multiple `--index` flags are provided,
     /// earlier values take priority.
+    ///
+    /// Index names are not supported as values. Relative paths must be disambiguated from index
+    /// names with `./` or `../` on Unix or `.\\`, `..\\`, `./` or `../` on Windows.
     //
     // The nested Vec structure (`Vec<Vec<Maybe<Index>>>`) is required for clap's
     // value parsing mechanism, which processes one value at a time, in order to handle

crates/uv-distribution-types/Cargo.toml

@@ -29,6 +29,7 @@ uv-platform-tags = { workspace = true }
 uv-pypi-types = { workspace = true }
 uv-redacted = { workspace = true }
 uv-small-str = { workspace = true }
+uv-warnings = { workspace = true }
 
 arcstr = { workspace = true }
 bitflags = { workspace = true }

crates/uv-distribution-types/src/index_url.rs

@@ -12,6 +12,7 @@ use url::{ParseError, Url};
 
 use uv_pep508::{Scheme, VerbatimUrl, VerbatimUrlError, split_scheme};
 use uv_redacted::DisplaySafeUrl;
+use uv_warnings::warn_user;
 
 use crate::{Index, IndexStatusCodeStrategy, Verbatim};
 
@@ -140,6 +141,30 @@ impl IndexUrl {
             Cow::Owned(url)
         }
     }
+
+    /// Warn user if the given URL was provided as an ambiguous relative path.
+    ///
+    /// This is a temporary warning. Ambiguous values will not be
+    /// accepted in the future.
+    pub fn warn_on_disambiguated_relative_path(&self) {
+        let Self::Path(verbatim_url) = &self else {
+            return;
+        };
+
+        if let Some(path) = verbatim_url.given() {
+            if !is_disambiguated_path(path) {
+                if cfg!(windows) {
+                    warn_user!(
+                        "Relative paths passed to `--index` or `--default-index` should be disambiguated from index names (use `.\\{path}` or `./{path}`). Support for ambiguous values will be removed in the future"
+                    );
+                } else {
+                    warn_user!(
+                        "Relative paths passed to `--index` or `--default-index` should be disambiguated from index names (use `./{path}`). Support for ambiguous values will be removed in the future"
+                    );
+                }
+            }
+        }
+    }
 }
 
 impl Display for IndexUrl {
@@ -162,6 +187,28 @@ impl Verbatim for IndexUrl {
     }
 }
 
+/// Checks if a path is disambiguated.
+///
+/// Disambiguated paths are absolute paths, paths with valid schemes,
+/// and paths starting with "./" or "../" on Unix or ".\\", "..\\",
+/// "./", or "../" on Windows.
+fn is_disambiguated_path(path: &str) -> bool {
+    if cfg!(windows) {
+        if path.starts_with(".\\") || path.starts_with("..\\") || path.starts_with('/') {
+            return true;
+        }
+    }
+    if path.starts_with("./") || path.starts_with("../") || Path::new(path).is_absolute() {
+        return true;
+    }
+    // Check if the path has a scheme (like `file://`)
+    if let Some((scheme, _)) = split_scheme(path) {
+        return Scheme::parse(scheme).is_some();
+    }
+    // This is an ambiguous relative path
+    false
+}
+
 /// An error that can occur when parsing an [`IndexUrl`].
 #[derive(Error, Debug)]
 pub enum IndexUrlError {
@@ -625,3 +672,41 @@ impl IndexCapabilities {
             .insert(Flags::FORBIDDEN);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_index_url_parse_valid_paths() {
+        // Absolute path
+        assert!(is_disambiguated_path("/absolute/path"));
+        // Relative path
+        assert!(is_disambiguated_path("./relative/path"));
+        assert!(is_disambiguated_path("../../relative/path"));
+        if cfg!(windows) {
+            // Windows absolute path
+            assert!(is_disambiguated_path("C:/absolute/path"));
+            // Windows relative path
+            assert!(is_disambiguated_path(".\\relative\\path"));
+            assert!(is_disambiguated_path("..\\..\\relative\\path"));
+        }
+    }
+
+    #[test]
+    fn test_index_url_parse_ambiguous_paths() {
+        // Test single-segment ambiguous path
+        assert!(!is_disambiguated_path("index"));
+        // Test multi-segment ambiguous path
+        assert!(!is_disambiguated_path("relative/path"));
+    }
+
+    #[test]
+    fn test_index_url_parse_with_schemes() {
+        assert!(is_disambiguated_path("file:///absolute/path"));
+        assert!(is_disambiguated_path("https://registry.com/simple/"));
+        assert!(is_disambiguated_path(
+            "git+https://github.com/example/repo.git"
+        ));
+    }
+}

crates/uv/src/settings.rs

@@ -1333,6 +1333,12 @@ impl AddSettings {
             )
             .collect::<Vec<_>>();
 
+        // Warn user if an ambiguous relative path was passed as a value for
+        // `--index` or `--default-index`.
+        indexes
+            .iter()
+            .for_each(|index| index.url().warn_on_disambiguated_relative_path());
+
         // If the user passed an `--index-url` or `--extra-index-url`, warn.
         if installer
             .index_args

crates/uv/tests/it/edit.rs

@@ -9364,7 +9364,7 @@ fn add_index_with_existing_relative_path_index() -> Result<()> {
     let wheel_dst = packages.child("ok-1.0.0-py3-none-any.whl");
     fs_err::copy(&wheel_src, &wheel_dst)?;
 
-    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("./test-index"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
@@ -9393,7 +9393,7 @@ fn add_index_with_non_existent_relative_path() -> Result<()> {
         dependencies = []
     "#})?;
 
-    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("./test-index"), @r"
     success: false
     exit_code: 2
     ----- stdout -----
@@ -9423,7 +9423,7 @@ fn add_index_with_non_existent_relative_path_with_same_name_as_index() -> Result
         url = "https://pypi-proxy.fly.dev/simple"
     "#})?;
 
-    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("./test-index"), @r"
     success: false
     exit_code: 2
     ----- stdout -----
@@ -9446,12 +9446,16 @@ fn add_index_empty_directory() -> Result<()> {
         version = "0.1.0"
         requires-python = ">=3.12"
         dependencies = []
+
+        [[tool.uv.index]]
+        name = "test-index"
+        url = "https://pypi-proxy.fly.dev/simple"
     "#})?;
 
     let packages = context.temp_dir.child("test-index");
     packages.create_dir_all()?;
 
-    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    uv_snapshot!(context.filters(), context.add().arg("iniconfig").arg("--index").arg("./test-index"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
@@ -9467,6 +9471,46 @@ fn add_index_empty_directory() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn add_index_with_ambiguous_relative_path() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let mut filters = context.filters();
+    filters.push((r"\./|\.\\\\", r"[PREFIX]"));
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+    "#})?;
+
+    #[cfg(unix)]
+    uv_snapshot!(filters, context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: Relative paths passed to `--index` or `--default-index` should be disambiguated from index names (use `[PREFIX]test-index`). Support for ambiguous values will be removed in the future
+    error: Directory not found for index: file://[TEMP_DIR]/test-index
+    ");
+
+    #[cfg(windows)]
+    uv_snapshot!(filters, context.add().arg("iniconfig").arg("--index").arg("test-index"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: Relative paths passed to `--index` or `--default-index` should be disambiguated from index names (use `[PREFIX]test-index` or `[PREFIX]test-index`). Support for ambiguous values will be removed in the future
+    error: Directory not found for index: file://[TEMP_DIR]/test-index
+    ");
+
+    Ok(())
+}
+
 /// Add a PyPI requirement.
 #[test]
 fn add_group_comment() -> Result<()> {