Add support for Hatch's `{root:uri}` paths in editable installs (#2492)

## Summary

If a package uses Hatch's `root.uri` feature, we currently error:

```toml
dependencies = [
  "black @ {root:uri}/../black_editable"
]
```

Even though we're using PEP 517 hooks to get the metadata, which
_should_ support this. The problem is that we load the full
`PyProjectToml`, which means we parse the requirements, which means we
reject what looks like a relative URL in dependencies.

Instead, we should only enforce a limited subset of `pyproject.toml`
(arguably none).

Closes https://github.com/astral-sh/uv/issues/2475.

Cargo.lock

@@ -4301,6 +4301,7 @@ dependencies = [
  "insta",
  "itertools 0.12.1",
  "once_cell",
+ "pep440_rs",
  "pep508_rs",
  "pypi-types",
  "pyproject-toml",

crates/uv-build/Cargo.toml

@@ -15,6 +15,7 @@ workspace = true
 
 [dependencies]
 distribution-types = { path = "../distribution-types" }
+pep440_rs = { path = "../pep440-rs" }
 pep508_rs = { path = "../pep508-rs" }
 pypi-types = { path = "../pypi-types" }
 uv-fs = { path = "../uv-fs" }

crates/uv-build/src/lib.rs

@@ -15,7 +15,6 @@ use fs_err as fs;
 use indoc::formatdoc;
 use itertools::Itertools;
 use once_cell::sync::Lazy;
-use pyproject_toml::Project;
 use regex::Regex;
 use rustc_hash::FxHashMap;
 use serde::de::{value, SeqAccess, Visitor};
@@ -27,6 +26,7 @@ use tokio::sync::Mutex;
 use tracing::{debug, info_span, instrument, Instrument};
 
 use distribution_types::Resolution;
+use pep440_rs::{Version, VersionSpecifiers};
 use pep508_rs::Requirement;
 use uv_fs::Simplified;
 use uv_interpreter::{Interpreter, PythonEnvironment};
@@ -193,7 +193,7 @@ impl Error {
     }
 }
 
-/// A pyproject.toml as specified in PEP 517
+/// A pyproject.toml as specified in PEP 517.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 #[serde(rename_all = "kebab-case")]
 pub struct PyProjectToml {
@@ -203,6 +203,18 @@ pub struct PyProjectToml {
     pub project: Option<Project>,
 }
 
+/// The `[project]` section of a pyproject.toml as specified in PEP 621.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
+#[serde(rename_all = "kebab-case")]
+pub struct Project {
+    /// The name of the project
+    pub name: String,
+    /// The version of the project as supported by PEP 440
+    pub version: Option<Version>,
+    /// The Python version requirements of the project
+    pub requires_python: Option<VersionSpecifiers>,
+}
+
 /// The `[build-system]` section of a pyproject.toml as specified in PEP 517.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 #[serde(rename_all = "kebab-case")]

crates/uv/tests/pip_compile.rs

@@ -5150,3 +5150,39 @@ requires-python = "<=3.8"
 
     Ok(())
 }
+
+/// Build an editable package with Hatchling's {root:uri} feature.
+#[test]
+fn compile_root_uri() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("-e ${ROOT_PATH}")?;
+
+    // In addition to the standard filters, remove the temporary directory from the snapshot.
+    let filters: Vec<_> = [(r"file://.*/", "file://[TEMP_DIR]/")]
+        .into_iter()
+        .chain(INSTA_FILTERS.to_vec())
+        .collect();
+
+    let root_path = current_dir()?.join("../../scripts/editable-installs/root_editable");
+    uv_snapshot!(filters, context.compile()
+        .arg("requirements.in")
+        .env("ROOT_PATH", root_path.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] --exclude-newer 2023-11-18T12:00:00Z requirements.in
+    -e ${ROOT_PATH}
+    black @ file://[TEMP_DIR]/black_editable
+        # via root-editable
+
+    ----- stderr -----
+    Built 1 editable in [TIME]
+    Resolved 2 packages in [TIME]
+    "###
+    );
+
+    Ok(())
+}

scripts/editable-installs/root_editable/pyproject.toml

@@ -0,0 +1,22 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "root-editable"
+description = 'A simple editable package with a {root:uri} dependency.'
+readme = "README.md"
+requires-python = ">=3.7"
+license = "MIT"
+keywords = []
+authors = [
+  { name = "Astral Software Inc.", email = "hey@astral.sh" },
+]
+classifiers = []
+dependencies = [
+  "black @ {root:uri}/../black_editable"
+]
+version = "0.1.0"
+
+[tool.hatch.metadata]
+allow-direct-references = true

scripts/editable-installs/root_editable/root_editable/__init__.py

@@ -0,0 +1,2 @@
+def func():
+    pass