Read persistent configuration from non-workspace pyproject.toml (#4526)

## Summary

If the user puts their configuration in a `pyproject.toml` that _isn't_
a valid workspace root (e.g., it's a Poetry file), we won't discover it,
because we only look in `uv.toml` files in that case. I think this is
somewhat debatable... We could choose to _require_ `uv.toml` there, but
as a user I'd probably expect it to work?

Closes https://github.com/astral-sh/uv/issues/4521.

Cargo.lock

@@ -4999,6 +4999,7 @@ dependencies = [
  "uv-normalize",
  "uv-resolver",
  "uv-toolchain",
+ "uv-warnings",
 ]
 
 [[package]]

crates/uv-settings/Cargo.toml

@@ -19,10 +19,11 @@ pep508_rs = { workspace = true }
 pypi-types = { workspace = true }
 uv-configuration = { workspace = true, features = ["schemars"] }
 uv-fs = { workspace = true }
+uv-macros = { workspace = true }
 uv-normalize = { workspace = true, features = ["schemars"] }
 uv-resolver = { workspace = true, features = ["schemars"] }
 uv-toolchain = { workspace = true, features = ["schemars"] }
-uv-macros = { workspace = true }
+uv-warnings = { workspace = true }
 
 dirs-sys = { workspace = true }
 fs-err = { workspace = true }

crates/uv-settings/src/lib.rs

@@ -4,6 +4,7 @@ use std::path::{Path, PathBuf};
 use tracing::debug;
 
 use uv_fs::Simplified;
+use uv_warnings::warn_user;
 
 pub use crate::combine::*;
 pub use crate::settings::*;
@@ -57,22 +58,25 @@ impl FilesystemOptions {
 
     /// Find the [`FilesystemOptions`] for the given path.
     ///
-    /// The search starts at the given path and goes up the directory tree until a `uv.toml` file is
+    /// The search starts at the given path and goes up the directory tree until a `uv.toml` file or
-    /// found.
+    /// `pyproject.toml` file is found.
     pub fn find(path: impl AsRef<Path>) -> Result<Option<Self>, Error> {
         for ancestor in path.as_ref().ancestors() {
-            // Read a `uv.toml` file in the current directory.
+            match Self::from_directory(ancestor) {
-            let path = ancestor.join("uv.toml");
+                Ok(Some(options)) => {
-            match fs_err::read_to_string(&path) {
+                    return Ok(Some(options));
-                Ok(content) => {
+                }
-                    let options: Options = toml::from_str(&content)
+                Ok(None) => {
-                        .map_err(|err| Error::UvToml(path.user_display().to_string(), err))?;
+                    // Continue traversing the directory tree.
-
+                }
-                    debug!("Found workspace configuration at `{}`", path.display());
+                Err(Error::PyprojectToml(file, _err)) => {
-                    return Ok(Some(Self(options)));
+                    // If we see an invalid `pyproject.toml`, warn but continue.
+                    warn_user!("Failed to parse `{file}` during settings discovery; skipping...");
+                }
+                Err(err) => {
+                    // Otherwise, warn and stop.
+                    return Err(err);
                 }
-                Err(err) if err.kind() == std::io::ErrorKind::NotFound => {}
-                Err(err) => return Err(err.into()),
             }
         }
         Ok(None)
@@ -103,9 +107,17 @@ impl FilesystemOptions {
                 let pyproject: PyProjectToml = toml::from_str(&content)
                     .map_err(|err| Error::PyprojectToml(path.user_display().to_string(), err))?;
                 let Some(tool) = pyproject.tool else {
+                    debug!(
+                        "Skipping `pyproject.toml` in `{}` (no `[tool]` section)",
+                        dir.as_ref().display()
+                    );
                     return Ok(None);
                 };
                 let Some(options) = tool.uv else {
+                    debug!(
+                        "Skipping `pyproject.toml` in `{}` (no `[tool.uv]` section)",
+                        dir.as_ref().display()
+                    );
                     return Ok(None);
                 };
 

crates/uv/tests/pip_compile.rs

@@ -3204,6 +3204,7 @@ fn override_dependency_from_workspace_invalid_syntax() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
+    warning: Failed to parse `pyproject.toml` during settings discovery; skipping...
     error: Failed to parse: `pyproject.toml`
       Caused by: TOML parse error at line 9, column 29
       |

crates/uv/tests/pip_install.rs

@@ -143,6 +143,7 @@ fn invalid_pyproject_toml_syntax() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
+    warning: Failed to parse `pyproject.toml` during settings discovery; skipping...
     error: Failed to parse: `pyproject.toml`
       Caused by: TOML parse error at line 1, column 5
       |

crates/uv/tests/show_settings.rs

@@ -2246,3 +2246,142 @@ fn resolve_user_configuration() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+/// Read from a `pyproject.toml` file in the current directory. In this case, the `pyproject.toml`
+/// file uses the Poetry schema.
+#[test]
+#[cfg_attr(
+    windows,
+    ignore = "Configuration tests are not yet supported on Windows"
+)]
+fn resolve_poetry_toml() -> anyhow::Result<()> {
+    let context = TestContext::new("3.12");
+
+    // Write a `uv.toml` file to the directory.
+    let config = context.temp_dir.child("pyproject.toml");
+    config.write_str(indoc::indoc! {r#"
+        [tool.poetry]
+        name = "project"
+        version = "0.1.0"
+
+        [tool.poetry.dependencies]
+        python = "^3.10"
+        rich = "^13.7.1"
+
+        [build-system]
+        requires = ["poetry-core"]
+        build-backend = "poetry.core.masonry.api"
+
+        [tool.uv.pip]
+        resolution = "lowest-direct"
+    "#})?;
+
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("anyio>3.0.0")?;
+
+    // Resolution should use the lowest direct version, and generate hashes.
+    uv_snapshot!(context.filters(), command(&context)
+        .arg("--show-settings")
+        .arg("requirements.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    GlobalSettings {
+        quiet: false,
+        verbose: 0,
+        color: Auto,
+        native_tls: false,
+        connectivity: Online,
+        isolated: false,
+        show_settings: true,
+        preview: Disabled,
+        toolchain_preference: OnlySystem,
+    }
+    CacheSettings {
+        no_cache: false,
+        cache_dir: Some(
+            "[CACHE_DIR]/",
+        ),
+    }
+    PipCompileSettings {
+        src_file: [
+            "requirements.in",
+        ],
+        constraint: [],
+        override: [],
+        overrides_from_workspace: [],
+        refresh: None(
+            Timestamp(
+                SystemTime {
+                    tv_sec: [TIME],
+                    tv_nsec: [TIME],
+                },
+            ),
+        ),
+        settings: PipSettings {
+            index_locations: IndexLocations {
+                index: None,
+                extra_index: [],
+                flat_index: [],
+                no_index: false,
+            },
+            python: None,
+            system: false,
+            extras: None,
+            break_system_packages: false,
+            target: None,
+            prefix: None,
+            index_strategy: FirstIndex,
+            keyring_provider: Disabled,
+            no_build_isolation: false,
+            build_options: BuildOptions {
+                no_binary: None,
+                no_build: None,
+            },
+            strict: false,
+            dependency_mode: Transitive,
+            resolution: LowestDirect,
+            prerelease: IfNecessaryOrExplicit,
+            output_file: None,
+            no_strip_extras: false,
+            no_annotate: false,
+            no_header: false,
+            custom_compile_command: None,
+            generate_hashes: false,
+            setup_py: Pep517,
+            config_setting: ConfigSettings(
+                {},
+            ),
+            python_version: None,
+            python_platform: None,
+            exclude_newer: Some(
+                ExcludeNewer(
+                    2024-03-25T00:00:00Z,
+                ),
+            ),
+            no_emit_package: [],
+            emit_index_url: false,
+            emit_find_links: false,
+            emit_build_options: false,
+            emit_marker_expression: false,
+            emit_index_annotation: false,
+            annotation_style: Split,
+            link_mode: Clone,
+            compile_bytecode: false,
+            require_hashes: false,
+            upgrade: None,
+            reinstall: None,
+            concurrency: Concurrency {
+                downloads: 50,
+                builds: 16,
+                installs: 8,
+            },
+        },
+    }
+
+    ----- stderr -----
+    "###
+    );
+
+    Ok(())
+}