fix: prevent RowsAffected double-counting when triggers fire

[dlevy-msft-sql]

Problem

When a DML statement (UPDATE/INSERT/DELETE) fires an AFTER trigger that does not use SET NOCOUNT ON, SQL Server sends two TDS tokens with row counts:

1. DONEINPROC (0xFD) - the trigger's DML row count
2. DONE (0xFF) - the outer statement's actual row count

The driver's iterateResponse() was accumulating (+=) both counts into rowCount, causing RowsAffected() to return the sum (e.g., 2 instead of 1 for a single-row update that fires a trigger inserting 1 audit row).

This matches the behavior reported in #204 where RowsAffected() returns incorrect values.

Root Cause

In token.go, iterateResponse() line 1200:

case doneStruct:
    if token.Status&doneCount != 0 {
        t.rowCount += int64(token.RowCount)  // BUG: accumulates trigger counts
    }

Fix

Change doneStruct handling from accumulation (+=) to assignment (=):

case doneStruct:
    if token.Status&doneCount != 0 {
        t.rowCount = int64(token.RowCount)  // Use authoritative outer count
    }

The final DONE/DONEPROC token carries the authoritative row count for the outermost statement. DONEINPROC tokens from sp_executesql still work correctly because the subsequent DONEPROC has status=0 (no doneCount flag set), so it doesn't overwrite.

Verified Scenarios

Scenario	Before	After
Basic UPDATE (no trigger)	1 ✅	1 ✅
UPDATE with trigger (no NOCOUNT)	2 ❌	1 ✅
UPDATE with trigger (SET NOCOUNT ON)	1 ✅	1 ✅
UPDATE all rows with trigger	3 ✅	3 ✅
Parameterized INSERT via sp_executesql	1 ✅	1 ✅

Tests

• Added TestRowsAffectedWithTrigger integration test covering all 4 scenarios
• Existing TestAffectedRows continues to pass
• All unit tests pass (./msdsn, ./internal/..., ./integratedauth, ./azuread)

Fixes #204

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.60%. Comparing base (65e137f) to head (c240049).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #363       +/-   ##
===========================================
+ Coverage   80.62%   96.60%   +15.98%     
===========================================
  Files          35       92       +57     
  Lines        6910    74360    +67450     
===========================================
+ Hits         5571    71837    +66266     
- Misses       1068     2188     +1120     
- Partials      271      335       +64     

Flag	Coverage Δ
unittests	96.53% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
token.go	70.09% <100.00%> (+0.56%)	⬆️

... and 58 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

Fixes incorrect RowsAffected() values when DML statements fire AFTER triggers that emit their own rowcount tokens, by ensuring the final DONE token’s count is treated as authoritative.

Changes:

• Update tokenProcessor.iterateResponse() to assign (not accumulate) DONE/DONEPROC row counts.
• Add unit tests validating rowcount assignment behavior in trigger-like and multi-statement token sequences.
• Add integration tests covering RowsAffected() with triggers (NOCOUNT on/off) and multi-statement batch behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
token.go	Changes DONE rowcount handling to avoid double-counting when triggers emit additional rowcount tokens.
token_test.go	Adds unit tests asserting the new rowcount assignment semantics.
rowsaffected_test.go	Adds integration coverage for trigger scenarios and multi-statement batch RowsAffected() behavior.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.