Source object access from ColumnSet - node.js

Question

I try to split a sub-object in my recordset when importing data with initCB properties of a Column in ColumnSet.
But when I use two different init functions for two different destination names but one source I get same result.
const cs = new pgp.helpers.ColumnSet([
'id',
{ name: 'source_id', prop: 'source', init: function(obj) { return obj.value.id; } },
{ name: 'source_name', prop: 'source', init: function(obj) { return obj.value.name; } },
], { table: 'test_table' });
const data = [
{ id: 1, source: { id: 1, name: 'source1' } },
{ id: 2, source: { id: 1, name: 'source1' } },
{ id: 3, source: { id: 2, name: 'source2' } },
];
const insert = pgp.helpers.insert(data, cs);
The result is:
INSERT INTO "test_table"("id","source_id","source_name") VALUES
(1,'source1','source1'),
(2,'source1','source1'),
(3,'source2','source2')
instead of expected:
INSERT INTO "test_table"("id","source_id","source_name") VALUES
(1,1,'source1'),
(2,1,'source1'),
(3,2,'source2')
It seems like second invocation of callback function for THE SAME source field overriding result of previous invocation of ANOTHER callback function on THIS source field.
How I can avoid this?
Or there is another way of splitting a sub-object during import?

Answer 1

Option prop doesn't quite work that way. It is there to remap the value to a different property name, but it does not supply the direct object reference.
Instead, use property source of the column descriptor, to reference the source object. Ironically, you called the property in your data source as well, which means you will have to use source twice in your reference:
const cs = new pgp.helpers.ColumnSet([
'id',
{name: 'source_id', init: c => c.source.source.id},
{name: 'source_name', init: c => c.source.source.name}
], {table: 'test_table'});
The first source is what pg-promise API supports, while the second is your data column name :)
Also, as per documentation, the API sets source and this to the same, so if you prefer the ES5 function syntax (looks cleaner for your example), then you can do this instead:
const cs = new pgp.helpers.ColumnSet([
'id',
{ name: 'source_id', init: function() {return this.source.id;}},
{ name: 'source_name', init: function() {return this.source.name;}},
], { table: 'test_table' });
Above we have this point at the source data object.