Test that scan refuses another schema version (closes #64)

The version-mismatch test only opened its database through
openReportDatabase, so nothing exercised the branch of initSchema that
stops scan on a database stamped with an unknown schema version. The
test now opens the same database through openScanDatabase too and
requires errSchemaVersion, and is renamed to match the unversioned-file
test beside it, which also covers both paths.

Model: opus-5-5

TODO.md

@@ -32,10 +32,6 @@
 - test that `scan` refuses a database with another schema version
   (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/64)
 
-- correct four inaccurate comments in `cancel_test.go` and rename
-  `walkCancelInFlightDirs` to `walkCancelInFlightFiles` (2026-10-04,
-  https://git.eeqj.de/sneak/sfdupes/issues/33)
-
 - test the `-x` filesystem-boundary rules in `subdirJob` (2026-10-04,
   https://git.eeqj.de/sneak/sfdupes/issues/17)
 

cancel_test.go

@@ -18,21 +18,11 @@ import (
 	"time"
 )
 
-// This file gathers the tests for scan cancellation and worker-pool
-// unwinding. Everything it exercises lives in scan.go, so by the repo's
-// convention of one test file per source file it would belong in
-// scan_test.go. It is kept separate on purpose: cancellation behaviour
-// cuts across both the walk pool and the hash pool as a single concern,
-// and scan_test.go is already over 1,600 lines. That is the deliberate
-// exception the convention otherwise expects to be stated.
-
-// poolUnwind bounds how long a test waits for a cancellation to take
-// effect: for a goroutine to return or a channel to close once its
-// context is cancelled, or for a signal to cancel the scan's context.
-// Only a failing run waits this long, and the bound is what makes that
-// failure an assertion instead of a hang. A call made without it, as
-// most of this file's scans are, has no bound: a regression that parks
-// it is caught only as the test binary's own timeout.
+// poolUnwind bounds how long a goroutine is given to leave a pool
+// after its context is cancelled. Only a failing run ever waits this
+// long: a pool that ignored its cancellation parks forever, and this
+// is what turns that into a failed assertion instead of a suite that
+// hangs until the test binary's own timeout.
 const poolUnwind = 2 * time.Second
 
 // walkClock is a context whose cancellation is driven by the scan's
@@ -43,14 +33,9 @@ const poolUnwind = 2 * time.Second
 //
 // The accounting behind the n chosen by each test: every blocking
 // channel operation in the walk selects on Done, so the walk spends
-// one consultation per file event plus a couple per directory. The
-// index load that runs ahead of it also consults Done, but a bounded
-// number of times that does not grow with the record count. The tests
-// depend on that property, not on the bound's exact value: each test
-// sets n from the consultations of the walk, plus those of the hash
-// phase when it cancels mid-hash, far from both ends of the phase it
-// interrupts, so the cancellation lands inside that phase whatever the
-// record count.
+// one consultation per file event plus a couple per directory, while
+// the index load that runs ahead of it spends a small fixed number
+// (three) whatever the record count.
 type walkClock struct {
 	n    int64
 	seen atomic.Int64
@@ -106,14 +91,11 @@ func (c *walkClock) Value(_ any) any {
 // directory still queued and only the handful already in flight can
 // emit anything more.
 const (
-	walkCancelDirs        = 100
-	walkCancelFilesPerDir = 20
-	walkCancelFiles       = walkCancelDirs * walkCancelFilesPerDir
-	walkCancelWorkers     = 4
-	// The most files the walkCancelWorkers directories already in
-	// flight when the scan is cancelled can still emit, at
-	// walkCancelFilesPerDir each. A file count, not a directory count.
-	walkCancelInFlightFiles = walkCancelWorkers * walkCancelFilesPerDir
+	walkCancelDirs         = 100
+	walkCancelFilesPerDir  = 20
+	walkCancelFiles        = walkCancelDirs * walkCancelFilesPerDir
+	walkCancelWorkers      = 4
+	walkCancelInFlightDirs = walkCancelWorkers * walkCancelFilesPerDir
 )
 
 // walkCancelAtDone is the consultation on which the fixture's context
@@ -176,11 +158,6 @@ func assertRecordsIntact(t *testing.T, db *sql.DB, before []string) {
 // unreachable, makes the scan carry its truncated view into the update
 // phase, which counts every record the walk never reached for removal.
 //
-// The syncScan call here is not bounded by poolUnwind: a regression
-// that left a worker pool parked would hang it, and that regression is
-// caught only by the test binary's own timeout, not by a quick
-// assertion.
-//
 //nolint:paralleltest // counts goroutines: must not run beside others
 func TestSyncScanCancelledMidWalkKeepsRecords(t *testing.T) {
 	dir := buildWalkCancelTree(t)
@@ -232,11 +209,10 @@ func assertWalkGuardAborted(t *testing.T, st scanStats, err error) {
 	}
 
 	// The workers drop every directory still queued once the scan is
-	// cancelled, so only the files in the directories already in flight
-	// can add to the census after the fact. A census beyond that bound
-	// would mean the cancellation was not observed where it should have
-	// been.
-	limit := walkCancelAtDone + walkCancelInFlightFiles
+	// cancelled, so only the directories already in flight can add to
+	// the census after the fact. A census beyond that bound would mean
+	// the cancellation was not observed where it should have been.
+	limit := walkCancelAtDone + walkCancelInFlightDirs
 	if st.unchanged > limit {
 		t.Errorf("census covers %d files, want at most %d: the walk kept "+
 			"taking directories off the queue after cancellation",
@@ -670,11 +646,7 @@ func TestDispatchDirsClosesJobsWhenCancelled(t *testing.T) {
 
 // TestFeedHashJobsClosesJobsWhenCancelled checks that the hash feeder
 // abandons the runs it has not queued yet and still closes the job
-// channel, which is what lets the workers' range terminate. The
-// receive on jobs below is not bounded: a feeder that returned without
-// closing jobs would leave that receive with no sender and no close, so
-// this regression is caught by the test binary's timeout rather than by
-// a bounded assertion.
+// channel, which is what lets the workers' range terminate.
 func TestFeedHashJobsClosesJobsWhenCancelled(t *testing.T) {
 	t.Parallel()
 
@@ -702,16 +674,6 @@ func TestFeedHashJobsClosesJobsWhenCancelled(t *testing.T) {
 // nobody wants the hashes of — while still letting the range run out
 // so the pool tears down. The queued run names a file that does not
 // exist, so a worker that hashed it anyway would produce a result.
-//
-// hashWorker's other cancellation exit, abandoning the send of a
-// result, is reachable from the scan: stop cancels the pool before it
-// drains results, so a worker waiting on that send can leave through
-// it. The tests that stop a scan mid-hash, among them
-// TestScanHashWriteFailureUnwindsPool, reach it in some runs only,
-// depending on timing, and no test fails without it, since stop's
-// drain frees a waiting worker anyway. This test, for its part, catches
-// a removed drop check in some runs only: a worker that hashes the run
-// anyway then picks at random between sending the result and leaving.
 func TestHashWorkerDropsQueuedRuns(t *testing.T) {
 	t.Parallel()
 
@@ -744,10 +706,7 @@ func TestHashWorkerDropsQueuedRuns(t *testing.T) {
 // TestHashPhaseCancelledReturnsContextError checks the result loop's
 // own exit: with the pool cancelled, no result will ever arrive, and
 // the loop must leave through the cancellation rather than wait for a
-// receive that cannot happen. This call is not bounded by poolUnwind: a
-// loop that dropped its cancellation case would block on that receive,
-// so the regression surfaces as the test binary's timeout rather than
-// as a bounded assertion.
+// receive that cannot happen.
 func TestHashPhaseCancelledReturnsContextError(t *testing.T) {
 	t.Parallel()