Biblatex prints white space plus period before PART field

Question

When I print the bibliography with a BOOK entry using the PART field, biblatex prints white space followed by a period before the PART field is printed. Is this a bug, or am I missing something?

\documentclass{article}
\usepackage{csquotes}
\usepackage[
        bibstyle = authoryear,
        citestyle = authoryear-comp,
        sorting = nyt,
        sortcites = false,
        language = american,
        abbreviate = false,
        backend = biber]{biblatex}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@BOOK{smith1965,
    AUTHOR = "John Smith",
    LOCATION = "London",
    NUMBER = "3",
    PART = "Part one",
    PUBLISHER = "Johnson Press",
    SERIES = "Classic books",
    TITLE = "A good book",  
    YEAR = "1965"}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\noindent
Text \parencite{smith1965}.
\printbibliography
\end{document}

Answer 1

BibLaTeX defines the directive to print the part as \DeclareFieldFormat{part}{.#1}

You can change it by

\DeclareFieldFormat{part}{#1}

The BibLaTeX manual specifies:

part field (literal)

The number of a partial volume. This field applies to books only, not to journals. It may be used when a logical volume consists of two or more physical ones. In this case the number of the logical volume goes in the volume field and the number of the part of that volume in the part field. See also volume.

Here is a redefinition of the printing directive that maintains consistency with BibLaTeX

\DeclareFieldFormat{part}{%
    \iffieldundef{volume}
        {#1}
        {.#1}%   
}