Hint at missing project.name

We got user reports where users were confused about why they can't use `[project.urls]` without other `pyproject.toml`. This PR adds a hint that (according to PEP 621), you need to set `project.name` when using any `project` fields`. (PEP 621 also requires `project.version` xor `dynamic = ["version"]`, but we check that later.)

The intermediate parsing layer to tell apart syntax errors from schema errors doesn't incur a performance penalty according to epage (toml-rs/toml#778 (comment)).

Closes #6419
Closes #6760

Cargo.toml

@@ -146,7 +146,7 @@ tokio-stream = { version = "0.1.14" }
 tokio-tar = { version = "0.3.1" }
 tokio-util = { version = "0.7.10", features = ["compat"] }
 toml = { version = "0.8.12" }
-toml_edit = { version = "0.22.13" }
+toml_edit = { version = "0.22.13", features = ["serde"] }
 tracing = { version = "0.1.40" }
 tracing-durations-export = { version = "0.3.0", features = ["plot"] }
 tracing-subscriber = { version = "0.3.18", features = ["env-filter", "json", "registry"] }

crates/pypi-types/Cargo.toml

@@ -29,6 +29,7 @@ rkyv = { workspace = true }
 serde = { workspace = true }
 thiserror = { workspace = true }
 toml = { workspace = true }
+toml_edit = { workspace = true }
 tracing = { workspace = true }
 url = { workspace = true }
 

crates/pypi-types/src/metadata.rs

@@ -6,6 +6,7 @@ use std::str::FromStr;
 use indexmap::IndexMap;
 use itertools::Itertools;
 use mailparse::{MailHeaderMap, MailParseError};
+use serde::de::IntoDeserializer;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use tracing::warn;
@@ -44,8 +45,12 @@ pub struct Metadata23 {
 pub enum MetadataError {
     #[error(transparent)]
     MailParse(#[from] MailParseError),
+    #[error("Invalid `pyproject.toml`")]
+    InvalidPyprojectTomlSyntax(#[source] toml_edit::TomlError),
+    #[error("`pyproject.toml` is using the `[project]` table, but the required `project.name` is not set.")]
+    InvalidPyprojectTomlMissingName(#[source] toml_edit::de::Error),
     #[error(transparent)]
-    Toml(#[from] toml::de::Error),
+    InvalidPyprojectTomlSchema(toml_edit::de::Error),
     #[error("metadata field {0} not found")]
     FieldNotFound(&'static str),
     #[error("invalid version: {0}")]
@@ -196,7 +201,7 @@ impl Metadata23 {
 
     /// Extract the metadata from a `pyproject.toml` file, as specified in PEP 621.
     pub fn parse_pyproject_toml(contents: &str) -> Result<Self, MetadataError> {
-        let pyproject_toml: PyProjectToml = toml::from_str(contents)?;
+        let pyproject_toml = PyProjectToml::from_toml(contents)?;
 
         let project = pyproject_toml
             .project
@@ -279,6 +284,23 @@ struct PyProjectToml {
     tool: Option<Tool>,
 }
 
+impl PyProjectToml {
+    fn from_toml(toml: &str) -> Result<Self, MetadataError> {
+        let pyproject_toml: toml_edit::ImDocument<_> = toml_edit::ImDocument::from_str(toml)
+            .map_err(MetadataError::InvalidPyprojectTomlSyntax)?;
+        let pyproject_toml: Self = PyProjectToml::deserialize(pyproject_toml.into_deserializer())
+            .map_err(|err| {
+            // TODO(konsti): A typed error would be nicer, this can break on toml upgrades.
+            if err.message().contains("missing field `name`") {
+                MetadataError::InvalidPyprojectTomlMissingName(err)
+            } else {
+                MetadataError::InvalidPyprojectTomlSchema(err)
+            }
+        })?;
+        Ok(pyproject_toml)
+    }
+}
+
 /// PEP 621 project metadata.
 ///
 /// This is a subset of the full metadata specification, and only includes the fields that are
@@ -435,7 +457,7 @@ pub struct RequiresDist {
 impl RequiresDist {
     /// Extract the [`RequiresDist`] from a `pyproject.toml` file, as specified in PEP 621.
     pub fn parse_pyproject_toml(contents: &str) -> Result<Self, MetadataError> {
-        let pyproject_toml: PyProjectToml = toml::from_str(contents)?;
+        let pyproject_toml = PyProjectToml::from_toml(contents)?;
 
         let project = pyproject_toml
             .project

crates/uv-build/Cargo.toml

@@ -35,6 +35,7 @@ tempfile = { workspace = true }
 thiserror = { workspace = true }
 tokio = { workspace = true }
 toml = { workspace = true }
+toml_edit = { workspace = true }
 tracing = { workspace = true }
 rustc-hash = { workspace = true }
 

crates/uv-build/src/lib.rs

@@ -7,7 +7,7 @@ use indoc::formatdoc;
 use itertools::Itertools;
 use regex::Regex;
 use rustc_hash::FxHashMap;
-use serde::de::{value, SeqAccess, Visitor};
+use serde::de::{value, IntoDeserializer, SeqAccess, Visitor};
 use serde::{de, Deserialize, Deserializer};
 use std::ffi::OsString;
 use std::fmt::{Display, Formatter};
@@ -82,7 +82,9 @@ pub enum Error {
     #[error("Invalid source distribution: {0}")]
     InvalidSourceDist(String),
     #[error("Invalid `pyproject.toml`")]
-    InvalidPyprojectToml(#[from] toml::de::Error),
+    InvalidPyprojectTomlSyntax(#[from] toml_edit::TomlError),
+    #[error("`pyproject.toml` does not match required schema. Note: When using any `[project]` field, at least `project.name` needs to be set.")]
+    InvalidPyprojectTomlSchema(#[from] toml_edit::de::Error),
     #[error("Editable installs with setup.py legacy builds are unsupported, please specify a build backend in pyproject.toml")]
     EditableSetupPy,
     #[error("Failed to install requirements from {0}")]
@@ -563,8 +565,12 @@ impl SourceBuild {
     ) -> Result<(Pep517Backend, Option<Project>), Box<Error>> {
         match fs::read_to_string(source_tree.join("pyproject.toml")) {
             Ok(toml) => {
+                let pyproject_toml: toml_edit::ImDocument<_> =
+                    toml_edit::ImDocument::from_str(&toml)
+                        .map_err(Error::InvalidPyprojectTomlSyntax)?;
                 let pyproject_toml: PyProjectToml =
-                    toml::from_str(&toml).map_err(Error::InvalidPyprojectToml)?;
+                    PyProjectToml::deserialize(pyproject_toml.into_deserializer())
+                        .map_err(Error::InvalidPyprojectTomlSchema)?;
                 let backend = if let Some(build_system) = pyproject_toml.build_system {
                     Pep517Backend {
                         // If `build-backend` is missing, inject the legacy setuptools backend, but

crates/uv-tool/Cargo.toml

@@ -31,5 +31,5 @@ pathdiff = { workspace = true }
 serde = { workspace = true }
 thiserror = { workspace = true }
 toml = { workspace = true }
-toml_edit = { workspace = true, features = ["serde"] }
+toml_edit = { workspace = true }
 tracing = { workspace = true }

crates/uv/tests/lock.rs

@@ -11810,3 +11810,50 @@ fn lock_implicit_virtual_path() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn invalid_project_table_dep() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("a/pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "a"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["b"]
+
+        [tool.uv.sources]
+        b = { path = "../b" }
+        "#,
+    )?;
+
+    let pyproject_toml = context.temp_dir.child("b/pyproject.toml");
+    pyproject_toml.write_str(
+        r"
+        [project.urls]
+        repository = 'https://github.com/octocat/octocat-python'
+        ",
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock().current_dir(context.temp_dir.join("a")), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    error: Failed to build: `b @ file://[TEMP_DIR]/b`
+      Caused by: Failed to extract static metadata from `pyproject.toml`
+      Caused by: `pyproject.toml` is using the `[project]` table, but the required `project.name` is not set.
+      Caused by: TOML parse error at line 2, column 10
+      |
+    2 |         [project.urls]
+      |          ^^^^^^^
+    missing field `name`
+
+    "###);
+
+    Ok(())
+}