chore: enable the modernize linter for idiomatic packages

.golangci.yaml

@@ -13,8 +13,11 @@
 #   - internal/reftest is a cgo differential harness (build tag refc); it is held
 #     to the idiomatic standard but exempted from a few cgo-hostile checks.
 #   - opus/, oggopus/, cmd/ are idiomatic Go at full strength.
-#   - modernize stays disabled: it panics on Go 1.26 + atomic types in
-#     golangci-lint v2 (known upstream bug), same as go-flac.
+#   - modernize runs on the idiomatic packages; inside the transliteration
+#     packages it joins the relaxed style linters, because its rangeint and
+#     loop rewrites fight diffability against the C. It stayed off until
+#     golangci-lint v2.13.2 on Go 1.27 fixed the v2 panic on atomic types
+#     (previously shared with go-flac).
 version: "2"
 output:
   sort-order:
@@ -38,6 +41,7 @@ linters:
     - iface
     - ineffassign
     - misspell
+    - modernize
     - nilerr
     - nilnil
     - predeclared
@@ -95,6 +99,7 @@ linters:
           - gocyclo
           - goconst
           - misspell
+          - modernize
           - prealloc
           - predeclared
           - revive
@@ -110,10 +115,13 @@ linters:
         linters:
           - staticcheck
         text: "(ST1003|ST1016|QF1|S1021)"
-      # cgo differential harness: cgo pointer patterns and C-mirroring names.
+      # cgo differential harness: cgo pointer patterns, C-mirroring names, and
+      # C-mirroring loops (modernize's rangeint rewrites fight diffability with
+      # the libopus reference the harness is checked against).
       - path: internal/reftest/
         linters:
           - gocritic
+          - modernize
           - revive
       # Test files: table-driven tests are naturally long and repetitive.
       - path: _test\.go

internal/packet/toc_test.go

@@ -53,7 +53,7 @@ func TestParseTOCConfigTable(t *testing.T) {
 		// Sweep the stereo flag and all four frame-count codes for each config
 		// to prove those low bits do not perturb the config decoding.
 		for _, stereo := range []bool{false, true} {
-			for code := uint8(0); code < 4; code++ {
+			for code := range uint8(4) {
 				b := tc.config<<3 | code
 				if stereo {
 					b |= 0x4

oggopus/decoder.go

@@ -200,10 +200,7 @@ func (d *Decoder) fill() (done bool, err error) {
 	}
 	// End-trim so the total delivered equals finalGranule - preSkip.
 	if d.limit >= 0 && d.delivered+int64(perChan) > d.limit {
-		keep := int(d.limit - d.delivered)
-		if keep < 0 {
-			keep = 0
-		}
+		keep := max(int(d.limit-d.delivered), 0)
 		samples = samples[:keep*d.info.Channels]
 		perChan = keep
 	}

oggopus/family1_test.go

@@ -257,10 +257,7 @@ func genInterleavedPCM(n, channels int) []int16 {
 // firstDiffByte returns the index of the first differing byte, or the shorter
 // length when one is a prefix of the other.
 func firstDiffByte(a, b []byte) int {
-	n := len(a)
-	if len(b) < n {
-		n = len(b)
-	}
+	n := min(len(b), len(a))
 	for i := range n {
 		if a[i] != b[i] {
 			return i

oggopus/writer.go

@@ -173,14 +173,11 @@ func (cw *containerWriter) writePacket(pkt []byte, samples48k int) error {
 // end-of-stream flag. close is idempotent.
 func (cw *containerWriter) close(sourceSamples int64) error {
 	if cw.hasHeld {
-		finalGranule := cw.preSkip + sourceSamples
 		// Guard monotonicity: the final granule must not regress below the
 		// previous page's cumulative count. This never triggers for consistent
 		// inputs; it defends against a caller passing a sourceSamples smaller
 		// than the already-committed audio.
-		if finalGranule < cw.granule {
-			finalGranule = cw.granule
-		}
+		finalGranule := max(cw.preSkip+sourceSamples, cw.granule)
 		if err := cw.sw.writeAudioPacket(cw.heldPacket, finalGranule); err != nil {
 			return err
 		}