fn new()

in guppy/src/graph/build.rs [79:134]
49 lines of code
3 McCabe index (conditional complexity)

    fn new(
        workspace_root: impl Into<Utf8PathBuf>,
        target_directory: impl Into<Utf8PathBuf>,
        metadata_table: serde_json::Value,
        packages: &HashMap<PackageId, PackageMetadataImpl>,
        members: impl IntoIterator<Item = PackageId>,
    ) -> Result<Self, Error> {
        use std::collections::btree_map::Entry;

        let workspace_root = workspace_root.into();
        // Build up the workspace members by path, since most interesting queries are going to
        // happen by path.
        let mut members_by_path = BTreeMap::new();
        let mut members_by_name = BTreeMap::new();
        for id in members {
            // Strip off the workspace path from the manifest path.
            let package_metadata = packages.get(&id).ok_or_else(|| {
                Error::PackageGraphConstructError(format!("workspace member '{}' not found", id))
            })?;

            let workspace_path = match &package_metadata.source {
                PackageSourceImpl::Workspace(path) => path,
                _ => {
                    return Err(Error::PackageGraphConstructError(format!(
                        "workspace member '{}' at path {:?} not in workspace",
                        id, package_metadata.manifest_path,
                    )));
                }
            };
            members_by_path.insert(workspace_path.to_path_buf(), id.clone());

            match members_by_name.entry(package_metadata.name.clone().into_boxed_str()) {
                Entry::Vacant(vacant) => {
                    vacant.insert(id.clone());
                }
                Entry::Occupied(occupied) => {
                    return Err(Error::PackageGraphConstructError(format!(
                        "duplicate package name in workspace: '{}' is name for '{}' and '{}'",
                        occupied.key(),
                        occupied.get(),
                        id
                    )))
                }
            }
        }

        Ok(Self {
            root: workspace_root,
            target_directory: target_directory.into(),
            metadata_table,
            members_by_path,
            members_by_name,
            #[cfg(feature = "proptest1")]
            name_list: OnceCell::new(),
        })
    }