"sub-library" should load "main library" by default

[Mo-Gul]

Loading the graphs.standard library without loading the graphs library as well leads to an error message. Wouldn't it be an improvement if the graphs.standard library would load the graph library itself (by default)?

\documentclass{standalone}
\usepackage{tikz}
    \usetikzlibrary{graphs.standard}
\begin{document}
\end{document}

Something similar holds for the graphdrawing library which also only makes sense when the graph library is loaded. In contrast to the previous MWE loading the graphdrawing only works fine, i.e. without raising an error.

\documentclass{standalone}
\usepackage{tikz}
    \usetikzlibrary{graphdrawing}
\begin{document}
\end{document}

[hmenke]

Excellent idea. I think the decorations.<whatever> libraries already do this and always load the decorations library, so it would just be consistent to have that for all others as well.

[Mo-Gul]

You are right regarding the decorations libraries. Shall I include this already in the current Pull Request or wait?

[Mo-Gul]

I added loading graphs in the graphs.standard library in my last commit to Pull Request #711.

Up to now I decided not to load the graphs library when graphdrawing is loaded because of the text I just read here:

pgf/doc/generic/pgf/text-en/pgfmanual-en-gd-usage-tikz.tex

Lines 75 to 80 in f5d0ffd

	Note that in addition to the graph \emph{drawing} libraries, you may also wish
	to load the normal \tikzname\ library |graphs|. It provides the powerful
	|graph| path command with its easy-to-use syntax for specifying graphs, but you
	can use the graph drawing engine independently of the |graphs| library, for
	instance in conjunction with the |child| or the |edge| syntax. Here is a
	typical setup:

I also could find some examples in the manual. One of them is

pgf/doc/generic/pgf/text-en/pgfmanual-en-gd-overview.tex

Lines 104 to 120 in f5d0ffd

	\begin{codeexample}[]
	\tikz [grow'=up, binary tree layout, nodes={circle,draw}]
	\node {1}
	child { node {2}
	child { node {3} }
	child { node {4}
	child { node {5} }
	child { node {6} }
	}
	}
	child { node {7}
	child { node {8}
	child[missing]
	child { node {9} }
	}
	};
	\end{codeexample}

I adapted the codeexamples accordingly in the above mentioned commit as well.