Group everything by Column A and have Column B be a comma-delimited list of values

Question

I've got a Google Sheets worksheet with data like this:

Product	Attribute
Product A	Cyan
Product B	Cyan
Product C	Cyan
Product A	Magenta
Product C	Magenta
Product B	Yellow
Product C	Yellow
Product A	Black
Product B	Black

What I'd like to do group everything by Column A and have Column B be a comma-delimited list of values that share Column A in common, like so:

Product	Attribute
Product A	Cyan,Magenta,Black
Product B	Cyan,Yellow,Black
Product C	Cyan,Magenta,Yellow,Black

Query? Arrayformula? Both?

Answer 1

use:

=ARRAYFORMULA(REGEXREPLACE(TRIM(SPLIT(FLATTEN(
 QUERY(QUERY({ROW(A1:A), A1:A&"×", B1:B&","}, 
 "select max(Col3) where not Col2 starts with '×' 
  group by Col1 pivot Col2"),,9^9)), "×")), ",$", ))

Answer 2

try:

={UNIQUE(FILTER(A:A, B:B<>"")), BYROW(UNIQUE(FILTER(A:A, B:B<>"")), 
 LAMBDA(aa, JOIN(", ", FILTER(B:B, A:A=aa))))}