How to UPSERT with optional updates?

I'm trying to write a script for an optional upsert. That is, it is just like a regular insert or update, but in
addition,the information of a given column should be updated, or be left as-is, is passed as well. That is: 

- Insert if does not exist.
- If exists, check the parameters to understand if a particular column should be updated, or be left as-is.

This is the script that I have so far:

INSERT INTO table_name (
  "col1",
  "col2",
  "col3",
  "col4",
  "col5",
  "col6",
  "col7"
)
SELECT DISTINCT
  a."col1",
  a."col2",
  a."col3",
  a."col4",
  a."col5",
  a."col6",
  a."col7"
FROM UNNEST (
  $1::uuid[],
  $2::uuid[],
  $3::numeric[],
  $4::numeric[],
  $5::boolean[],
  $6::boolean[],
  $7::timestamptz[],
  $8::boolean[],
  $9::boolean[],
  $10::boolean[]
) WITH ORDINALITY AS a(
  "col1",
  "col2",
  "col3",
  "col4",
  "col5",
  "col6",
  "col7",
  "shouldUpdateCol3",
  "shouldUpdateCol4",
  "shouldUpdateCol5",
  "ordinality"
)
ON CONFLICT
  ("col1", "col2")
DO UPDATE
SET
  "col3" = CASE WHEN EXCLUDED."shouldUpdateCol3" = TRUE THEN EXCLUDED."col3" ELSE table_name."col3" END,
  "col4" = CASE WHEN EXCLUDED."shouldUpdateCol4" = TRUE THEN EXCLUDED."col4" ELSE table_name."col4" END,
  "col5" = CASE WHEN EXCLUDED."shouldUpdateCol5" = TRUE THEN EXCLUDED."col5" ELSE table_name."col5" END,
  "col7" = EXCLUDED."col7";

It does not work, because the columns `shouldUpdateCol3`, `shouldUpdateCol4` and `shouldUpdateCol5` are not selected in
the`SELECT FROM UNNEST` above. 

However, if I add them to the `SELECT FROM UNNEST`, then I get `INSERT has more expressions than target columns` error.