What's the most robust way to efficiently parse CSV using awk?

Question

The intent of this question is to provide a canonical answer.

Given a CSV as might be generated by Excel or other tools with embedded newlines, embedded double quotes

Answer 1

An improvement upon @EdMorton's FPAT solution, which should be able to handle double-quotes(") escaped by doubling ("" -- as allowed by the CSV standard).

gawk -v FPAT='[^,]*|("[^"]*")+' ...

This STILL

1. isn't able to handle newlines inside quoted fields, which are perfectly legit in standard CSV files.

2. assumes GNU awk (gawk), a standard awk won't do.

Example:

$ echo 'a,,"","y""ck","""x,y,z"," ",12' |
gawk -v OFS='|' -v FPAT='[^,]*|("[^"]*")+' '{$1=$1}1'
a||""|"y""ck"|"""x,y,z"|" "|12

$ echo 'a,,"","y""ck","""x,y,z"," ",12' |
gawk -v FPAT='[^,]*|("[^"]*")+' '{
  for(i=1; i<=NF;i++){
    if($i~/"/){ $i = substr($i, 2, length($i)-2); gsub(/""/,"\"", $i) }
    print "<"$i">"
  }
}'

<>
<>

<"x,y,z>
< >
<12>