In ElementTree, when parsing a namespaced XML document (like a Maven POM), every element in the path must be namespaced. If child_text uses a helper like t(tag) to prepend the namespace, calling child_text(root, 'parent/version') will result in searching for {ns}parent/version (where version is namespace-less), which will fail to match the namespaced <version> element inside <parent>. This means get_version will always return None when a POM inherits its version from its parent.

To fix this, retrieve the parent element first and then get its version child.

If sub_modules is empty (meaning only the root POM . is being installed), running mvn install without -pl or -N will cause Maven to recursively build all modules defined in the root POM. In a sparse checkout, this will fail because those module directories are not checked out.

To prevent this, you should append the -N (non-recursive) flag when sub_modules is empty so that only the root POM itself is installed.

Parsing the XML content of the same POM files repeatedly (via ET.fromstring(pom_contents[local])) during dependency resolution can be highly inefficient, especially in a large monorepo with hundreds of modules.

We can introduce a simple cache for the parsed XML roots (pom_roots) to ensure each POM is parsed at most once. This cached helper can also be reused at line 260 (local_root = get_pom_root(local_parent)).

    pom_roots: dict[Path, ET.Element] = {}

    def get_pom_root(path: Path) -> ET.Element:
        if path not in pom_roots:
            pom_roots[path] = ET.fromstring(pom_contents[path])
        return pom_roots[path]

    def resolve_local(coord: Coord, declared_version: Optional[str]) -> Optional[Path]:
        """Local pom whose version matches the declared version, or None.

        - No coord match in the monorepo → None.
        - declared_version is None (regular dep inheriting from depMgmt) → follow
          the local pom optimistically; we'd need full Maven evaluation to know
          the resolved version, and in this monorepo unversioned deps virtually
          always inherit from a SNAPSHOT BOM.
        - Either version contains a Maven property (${…}) → follow optimistically.
        - Otherwise the versions must equal.
        """
        local = coord_to_pom.get(coord)
        if local is None:
            return None
        if declared_version is None:
            return local
        local_version = get_version(get_pom_root(local)) or ''
        if '${' in declared_version or '${' in local_version:
            return local
        return local if local_version == declared_version else None