How to attach Upvalues to CompoundExpression?

Question

I'm trying to make something like this work:

Evaluating

someData // Query[whatever...] /* summarizeInPrettyWay /* promptToRemoveCompoundExpression ;

should produce

(Please remove the semicolon and re-evaluate in order to see a summary of the data)

In words, I want to operate on some data (usually, in order to reduce it into a more manageable data set appropriate for some specific type of operation), prepare a summary of this reduced data set and allow the user of the Notebook to either see the summary or not (hence why I use a semicolon (;) at the end of the expression).

If the user decides not to remove the semicolon, when evaluating the cell (they evaluate a CompoundExpression) they will see a message informing them, that there is a summary of the data they just calculated, which they can review by removing the semicolon and re-evaluating the cell.

On the other hand, if the user decides to remove the semicolon (they evaluate a RightComposition) and evaluate, then the output is some summary description of the data without any message (prompting them to remove a semicolon, in order to see the summary).

The data are in the form of { <|key -> value, ...|>, ... }.

So far, I am failing.

---

Code:

This is the summary code:

funcs = {First, Last};
pretty = (Thread[{Length, Element} -> (MapAt[(Thread[funcs -> #]&) /* 
   Association, #, -1])] &) /* Association;
summary = (Through[{Length, Through[funcs[#]]&}[#]]&) /* pretty;

And here's a toy dataset:

toy = {
  <|"date"->"5/1/2021","x"->1,"y"->2,"z"->"alpha","w"->3.14|>,
  <|"date"->"6/2/2022","x"->3,"y"->4,"z"->"gamma","w"->2.72|>,
  <|"date"->"12/2/2021","x"->5,"y"->6,"z"->"beta","w"->1.41|>,
  <|"date"->"3/6/2021","x"->7,"y"->8,"z"->"alpha","w"->1.73|>,
  <|"date"->"4/4/2022","x"->9,"y"->10,"z"->"gamma","w"->2.23|>,
  <|"date"->"12/1/2021","x"->11,"y"->12,"z"->"alpha","w"->0.57|>,
  <|"date"->"5/1/2022","x"->13,"y"->14,"z"->"alpha","w"->1.61|>
};

This is what I came up with:

msg = "Please remove the semicolon and re-evaluate to see a summary";
prompt /: CompoundExpression[__, prompt] := Print[msg]
prompt /: RightComposition[__, prompt] := Identity

And here are the ways it fails:

1. toy // Query[Select[#z == "alpha" &]] /* summary /* Dataset /* prompt; doesn't print a message, as it should have.

2. toy // Query[Select[#z == "alpha" &]] /* summary /* Dataset /* prompt evaluates to

{
  <|date->5/1/2021,x->1,y->2,z->alpha,w->3.14|>,
  <|date->6/2/2022,x->3,y->4,z->gamma,w->2.72|>,
  <|date->12/2/2021,x->5,y->6,z->beta,w->1.41|>,
  <|date->3/6/2021,x->7,y->8,z->alpha,w->1.73|>,
  <|date->4/4/2022,x->9,y->10,z->gamma,w->2.23|>,
  <|date->12/1/2021,x->11,y->12,z->alpha,w->0.57|>,
  <|date->5/1/2022,x->13,y->14,z->alpha,w->1.61|>
}

when it should evaluate to

which is the expected output of toy // Query[Select[#z == "alpha" &]] /* summary /* Dataset (excluding the /* prompt)