Allow overriding module name for uv build backend (#11884)

Thank you for uv, it has game-changer capabilities in the field of
Python package and environment maangement!

## Summary

This is a small PR adding the option `module-name`
(`tool.uv.build-backend.module-name`) to the uv build backend (
https://github.com/astral-sh/uv/issues/8779 ).

Currently, the uv build backend will assume that the module name matches
the (dash to underdash-transformed) package name. In some packaging
scenarios this is not the case, and currently there exists no
possibility to override it, which this PR addresses.

From the main issue ( https://github.com/astral-sh/uv/issues/8779 ) I
could not tell if there is any extensive roadmap or plans how to
implement more complex scenarios, hence this PR as a suggestion for a
small feature with a big impact for certain scenarios.

I am new to Rust, I hope the borrow/reference usage is correct.

## Test Plan

So far I tested this at an example, if desired I can look into extending
the tests.

Fixes #11428

---------

Co-authored-by: konstin <konstin@mailbox.org>

crates/uv-build-backend/src/lib.rs

@@ -15,6 +15,7 @@ use thiserror::Error;
 use tracing::debug;
 use uv_fs::Simplified;
 use uv_globfilter::PortableGlobError;
+use uv_pypi_types::IdentifierParseError;
 
 #[derive(Debug, Error)]
 pub enum Error {
@@ -24,6 +25,8 @@ pub enum Error {
     Toml(#[from] toml::de::Error),
     #[error("Invalid pyproject.toml")]
     Validation(#[from] ValidationError),
+    #[error(transparent)]
+    Identifier(#[from] IdentifierParseError),
     #[error("Unsupported glob expression in: `{field}`")]
     PortableGlob {
         field: String,

crates/uv-build-backend/src/metadata.rs

@@ -17,7 +17,7 @@ use uv_pep440::{Version, VersionSpecifiers};
 use uv_pep508::{
     ExtraOperator, MarkerExpression, MarkerTree, MarkerValueExtra, Requirement, VersionOrUrl,
 };
-use uv_pypi_types::{Metadata23, VerbatimParsedUrl};
+use uv_pypi_types::{Identifier, Metadata23, VerbatimParsedUrl};
 
 use crate::serde_verbatim::SerdeVerbatim;
 use crate::Error;
@@ -803,7 +803,7 @@ pub(crate) struct ToolUv {
 /// When building the source distribution, the following files and directories are included:
 /// * `pyproject.toml`
 /// * The module under `tool.uv.build-backend.module-root`, by default
-///   `src/<project_name_with_underscores>/**`.
+///   `src/<module-name or project_name_with_underscores>/**`.
 /// * `project.license-files` and `project.readme`.
 /// * All directories under `tool.uv.build-backend.data`.
 /// * All patterns from `tool.uv.build-backend.source-include`.
@@ -812,7 +812,7 @@ pub(crate) struct ToolUv {
 ///
 /// When building the wheel, the following files and directories are included:
 /// * The module under `tool.uv.build-backend.module-root`, by default
-///   `src/<project_name_with_underscores>/**`.
+///   `src/<module-name or project_name_with_underscores>/**`.
 /// * `project.license-files` and `project.readme`, as part of the project metadata.
 /// * Each directory under `tool.uv.build-backend.data`, as data directories.
 ///
@@ -846,6 +846,15 @@ pub(crate) struct BuildBackendSettings {
     /// using the flat layout over the src layout.
     pub(crate) module_root: PathBuf,
 
+    /// The name of the module directory inside `module-root`.
+    ///
+    /// The default module name is the package name with dots and dashes replaced by underscores.
+    ///
+    /// Note that using this option runs the risk of creating two packages with different names but
+    /// the same module names. Installing such packages together leads to unspecified behavior,
+    /// often with corrupted files or directory trees.
+    pub(crate) module_name: Option<Identifier>,
+
     /// Glob expressions which files and directories to additionally include in the source
     /// distribution.
     ///
@@ -877,6 +886,7 @@ impl Default for BuildBackendSettings {
     fn default() -> Self {
         Self {
             module_root: PathBuf::from("src"),
+            module_name: None,
             source_include: Vec::new(),
             default_excludes: true,
             source_exclude: Vec::new(),

crates/uv-build-backend/src/source_dist.rs

@@ -8,11 +8,13 @@ use globset::{Glob, GlobSet};
 use std::io;
 use std::io::{BufReader, Cursor};
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 use tar::{EntryType, Header};
 use tracing::{debug, trace};
 use uv_distribution_filename::{SourceDistExtension, SourceDistFilename};
 use uv_fs::Simplified;
 use uv_globfilter::{parse_portable_glob, GlobDirFilter};
+use uv_pypi_types::Identifier;
 use uv_warnings::warn_user_once;
 use walkdir::WalkDir;
 
@@ -65,11 +67,21 @@ fn source_dist_matcher(
     let mut includes: Vec<String> = settings.source_include;
     // pyproject.toml is always included.
     includes.push(globset::escape("pyproject.toml"));
+
+    let module_name = if let Some(module_name) = settings.module_name {
+        module_name
+    } else {
+        // Should never error, the rules for package names (in dist-info formatting) are stricter
+        // than those for identifiers
+        Identifier::from_str(pyproject_toml.name().as_dist_info_name().as_ref())?
+    };
+    debug!("Module name: `{:?}`", module_name);
+
     // The wheel must not include any files included by the source distribution (at least until we
     // have files generated in the source dist -> wheel build step).
     let import_path = &settings
         .module_root
-        .join(pyproject_toml.name().as_dist_info_name().as_ref())
+        .join(module_name.as_ref())
         .portable_display()
         .to_string();
     includes.push(format!("{}/**", globset::escape(import_path)));

crates/uv-build-backend/src/wheel.rs

@@ -1,11 +1,11 @@
-use std::io::{BufReader, Read, Write};
-use std::path::{Path, PathBuf};
-use std::{io, mem};
-
 use fs_err::File;
 use globset::{GlobSet, GlobSetBuilder};
 use itertools::Itertools;
 use sha2::{Digest, Sha256};
+use std::io::{BufReader, Read, Write};
+use std::path::{Path, PathBuf};
+use std::str::FromStr;
+use std::{io, mem};
 use tracing::{debug, trace};
 use walkdir::WalkDir;
 use zip::{CompressionMethod, ZipWriter};
@@ -14,6 +14,7 @@ use uv_distribution_filename::WheelFilename;
 use uv_fs::Simplified;
 use uv_globfilter::{parse_portable_glob, GlobDirFilter};
 use uv_platform_tags::{AbiTag, LanguageTag, PlatformTag};
+use uv_pypi_types::Identifier;
 use uv_warnings::warn_user_once;
 
 use crate::metadata::{BuildBackendSettings, DEFAULT_EXCLUDES};
@@ -128,7 +129,17 @@ fn write_wheel(
         return Err(Error::AbsoluteModuleRoot(settings.module_root.clone()));
     }
     let strip_root = source_tree.join(settings.module_root);
-    let module_root = strip_root.join(pyproject_toml.name().as_dist_info_name().as_ref());
+
+    let module_name = if let Some(module_name) = settings.module_name {
+        module_name
+    } else {
+        // Should never error, the rules for package names (in dist-info formatting) are stricter
+        // than those for identifiers
+        Identifier::from_str(pyproject_toml.name().as_dist_info_name().as_ref())?
+    };
+    debug!("Module name: `{:?}`", module_name);
+
+    let module_root = strip_root.join(module_name.as_ref());
     if !module_root.join("__init__.py").is_file() {
         return Err(Error::MissingModule(module_root));
     }