Tikz arrow with unwanted arrow-head

Question

I am sorry for the unspecific question title, but I didn't really know what to put there.

The question

I defined a command to make drawing arrows in Tikz easier for me, for the purpose of commutative diagrams. The syntax is supposed to look something like \arrow[ARROW OPTIONS]{src}{tgt}{label}[LABEL OPTIONS]. The command is defined as

\NewDocumentCommand{\arrow}{ommmo}{
    \IfNoValueTF{#1}{
        \IfNoValueTF{#5}{
            \draw[->] (#2) edge[decorate] node[font=\footnotesize] {\ensuremath{#4}} (#3);
        }{
            \draw[->] (#2) edge[decorate] node[#5,font=\footnotesize] {\ensuremath{#4}} (#3);
        }
    }{
        \IfNoValueTF{#5}{
            \draw[->,#1] (#2) edge[decorate,#1] node[font=\footnotesize] {\ensuremath{#4}} (#3);
        }{
            \draw[->,#1] (#2) edge[decorate,#1] node[#5,font=\footnotesize] {\ensuremath{#4}} (#3);
        }
    }
}

In most instances the code works perfectly fine, assuming I have defined nodes and use it like

\node (src) at (-1,0) {};
\node (tgt) at (1,0) {};
\arrow{src}{tgt}{}

However, if I skip defining nodes and use it like

\arrow{-1,0}{1,0}{}

suddenly a new arrow-head appears at the source of the arrow, always pointing upwards. Since the lengths of the arrows in the MWE below differ I think it has something to do with the way paths adapt to nodes. But since the background of the nodes is opaque I could not figure out why said additional arrow-head appears and I would really appreciate your help. Thank you.

MWE

% --- begin package declaration
\documentclass{article}

\usepackage{xparse} % better command definition
\usepackage{xstring} % strings
\usepackage{tikz}
    \usetikzlibrary{matrix} % node placement
    \usetikzlibrary{calc} % calculation
    \usetikzlibrary{decorations.pathmorphing} %snaked
    \usetikzlibrary{arrows} % right hook->
    \usetikzlibrary{arrows.meta} % -Implies

% --- tikz styles and commands
\tikzset{diagram/.append style={
    baseline={($(current bounding box.center) + (0pt,-0.15\baselineskip)$)}
}}

\tikzset{objects/.append style={
    matrix of nodes,
    ampersand replacement=\&, % replaces the column indicator from & to \&
    text height=1.75ex, text depth=0.5ex, % fixes some text alignment issues with nodes
    column sep={5em,between origins}, row sep={4.5em,between origins} % width of node does not influence column spacing
}}

\tikzset{equals/.append style={
    -,
    double,
    double distance=0.2em
}}
\tikzset{incl/.append style={right hook->}}
\tikzset{epi/.append style={->>}}
\tikzset{mono/.append style={>->}}
\tikzset{mapsto/.append style={|->}}
\tikzset{implies/.append style={
    arrows={-Implies},
    double,
    double distance=0.2em
}}

\tikzset{snaked/.append style={
    decoration={
        snake,
        amplitude=.4mm,
        segment length=2mm,
        pre length=1mm,
        post length=1mm
    }
}}
\tikzset{zigzaged/.append style={
    decoration={
        zigzag,
        amplitude=.4mm,
        segment length=2mm,
        pre length=1mm,
        post length=1mm
    }
}}

\NewDocumentEnvironment{diagram}{}{
    \tikzpicture[diagram]
}{
    \endtikzpicture
}

\NewDocumentCommand{\arrow}{ommmo}{
    \IfNoValueTF{#1}{
        \IfNoValueTF{#5}{
            \draw[->] (#2) edge[decorate] node[font=\footnotesize] {\ensuremath{#4}} (#3);
        }{
            \draw[->] (#2) edge[decorate] node[#5,font=\footnotesize] {\ensuremath{#4}} (#3);
        }
    }{
        \IfNoValueTF{#5}{
            \draw[->,#1] (#2) edge[decorate,#1] node[font=\footnotesize] {\ensuremath{#4}} (#3);
        }{
            \draw[->,#1] (#2) edge[decorate,#1] node[#5,font=\footnotesize] {\ensuremath{#4}} (#3);
        }
    }
}

\begin{document}
    \begin{diagram}
        \node (src) at (-1,0) {};
        \node (tgt) at (1,0) {};
        \arrow{src}{tgt}{}
    \end{diagram}

    \begin{diagram}
        \arrow{-1,0}{1,0}{}
    \end{diagram}
\end{document}

Answer 1

I've had pretty much the same problem recently. In the definition of \arrow, replace \draw with \path. I don't really understand why that works or is even necessary, though.