fix(orm): keep nested partial-select object when leftJoin first column is null

[barobaonguyen]

Closes #1603.

Root cause

mapResultRow (drizzle-orm/src/utils.ts) builds a per-row nullifyMap that decides which nested-object paths should be replaced with null when their left-joined table didn't match. The flag for a path is set on the first column it sees being null, and only cleared when a column from a different table later appears under the same path.

When the second (and later) columns under that path come from the same nullable left-joined table, the existing branch isn't taken — even if those columns are non-null. So a select like:

db.select({
  name: org.name,
  branding: {
    logo: brand.logo,             // null in the joined row
    panelBackground: brand.panel, // "#1a8cff"
  },
}).from(org).leftJoin(brand, ...)

returns branding: null instead of branding: { logo: null, panelBackground: "#1a8cff" }. Swapping the column order in the select hides the bug, which matches every report on the issue.

Fix

Also clear the flag when a non-null value arrives for the same path, not only on a table mismatch. Two-line condition change in mapResultRow:

} else if (
    typeof nullifyMap[objectName] === 'string'
    && (nullifyMap[objectName] !== tableName || value !== null)
) {
    nullifyMap[objectName] = false;
}

Tests

New drizzle-orm/tests/mapResultRow.test.ts (pnpm test → 7 new, 573 total passing):

• repro from the issue (first nested col null, later non-null → object preserved)
• column-order control (last col null, earlier non-null → object preserved)
• all-null on nullable join → object nullified
• all-null on inner join → object preserved (join guarantees non-null)
• mixed-table nested keys → never nullified
• two independent nested objects with different null patterns
• non-Column field with no joinsNotNullableMap → unchanged behaviour

Prior art

Equivalent one-line variants land in #1825 (2024), #5436, #5750, #5765, #5785, #5793. None of those PRs ship a regression-test file; the new test covers the surrounding invariants so the bug stays fixed under future refactors of nullifyMap.