Why does this custom "mytarget/mylink" definition pair NOT work properly?

Question

The goal is to get a pair of commands, \mytarget(*) and \mylink/\Mylink. Specifically, I am interested why "my" solution does NOT work, and how to fix it (if possible).

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Syntax

• \mytarget{<label name>}{<Text to display>}

  \mytarget*{<label name>}{<Text to display>}

• \mylink{<label name>}{<Text to instead display / could be empty>}

  \mylink{<label name>}{<Text to instead display / could be empty>}

Usage

1. The command \mytarget is intended as an anchor that can be referenced before/after its usage in document.

   • Unstarred version, \mytarget, is also part of the text. For example, bla bla \mytarget{label name here}{123} uh uh should give bla bla 123 uh uh, and the "123" part could be referenced earlier/later by \mylink/\Mylink.
   • Starred version, \mytarget*, is not part of the text. So bla bla \mytarget*{label name here}{123} uh uh should give bla bla uh uh, and the "123" part could be referenced earlier/later by \mylink/\Mylink. Notice there is no "123" visible here.

2. The commands \mylink/\Mylink display the links to a corresponding \mytarget.

   • For example, bla bla \mytarget*{label name here}{123} uh uh \mylink{label name here}{} would yield bla bla uh uh 123. The "123" part here is a link to the spot between "bla bla" and "uh uh". (Of course, this example is ridiculous and, of course, in reality the link leads to the line itself).
   • If the second argument for \mylink{}{}/\Mylink{}{} is given, it should override the original second argument of \mytarget(*). For instance, bla bla \mytarget*{label name here}{123} uh uh \mylink{label name here}{654} should give bla bla uh uh 654. The "654" part is again a link.
   • The difference between \mylink/\Mylink is that \mylink is faithful to the second argument of \mytarget(*){}{}. Whereas \Mylink does everything the same way expect \Mylink capitalises the first letter of the second argument. So bla bla \mytarget*{label name here}{turtle} uh uh \mylink{label name here}{} would give bla bla uh uh turtle; whereas bla bla \mytarget*{label name here}{turtle} uh uh \Mylink{label name here}{} yields bla bla uh uh Turtle. Notice that "turtle" is capitalised to "Turtle" in the second case. In both cases, "turtle" and "Turtle" are links.

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Effort

Based on helpful comments from Marijn, I was led to this answer and package crossreftools. Here is what I tried:

\documentclass[12pt]{book}
\usepackage{amsmath}
\usepackage{aligned-overset}
\usepackage{commath}
\usepackage[shortlabels]{enumitem}
\usepackage[colorlinks=true, linkcolor=blue, hypertexnames=false]{hyperref}
\usepackage{crossreftools}
\makeatletter
    \newcommand{\mytarget}{@ifstar{@mytargetstar}{@mytargetnostar}}
    \newcommand{@mytargetstar}[2]{\crtcrossreflabel*{#2}[#1]@ifnextchar\space{\hspace{-1sp}}{}}
    \newcommand{@mytargetnostar}[2]{\crtcrossreflabel{#2}[#1]@ifnextchar\space{\hspace{-1sp}}{}}
\DeclareRobustCommand{\mylink}[2]{%
    \if\relax\detokenize{#2}\relax
        \crtnameref{#1}
    \else
        \crthyperlink{#1}{#2}
    \fi
    \@ifnextchar\space{\hspace{-1sp}}{}
    }

\DeclareRobustCommand{\Mylink}[2]{%
    \if\relax\detokenize{#2}\relax
        \crtunameref{#1}
    \else
        \crthyperlink{#1}{\MakeUppercase #2}
    \fi
    \@ifnextchar\space{\hspace{-1sp}}{}
    }

\makeatother
\begin{document}
a b c \mytarget*{anchor}{I0--I1} d e f

\newpage
Why doesn't the link of \mylink{anchor}{ullallaa} lead anywhere?


\end{document}

Problems with my effort

1. Why doesn't the link of \mylink{anchor}{ullallaa} lead anywhere?
2. (Not compulsory) Should I change the remaining three newcommands into \DeclareRobustCommands?
3. (Not compulsory) Is there a better way to get rid of spaces than putting \@ifnextchar\space{\hspace{-1sp}}{} everywhere?

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I am running pdflatex 3.141592653-2.6-1.40.22 (MikTeX 21.3), and every package in my local distrubution was updated on 28/04/2021. Output is identical (in terms of errors, and what link doesn't work without the 3 packages) on Overleaf with default settings.

Answer 1

At some time your question was readable but with all the edits you are overstressing me.

I guess you are looking for \nameref, so something like this (without all the stars and variants):

\documentclass{article}
\usepackage{hyperref}
\makeatletter
\newcommand\mytarget[2]{\phantomsection\NR@gettitle{#2}\label{#1}#2}
\newcommand\mylink[1]{\nameref{#1}}
\makeatother
\begin{document}
\mytarget{blub}{TARGET}
\newpage
\mylink{blub}
\end{document}