Bound retained Go command diagnostics

internal/gotool/performance_test.go

@@ -20,36 +20,45 @@ func BenchmarkPerformanceCombinedOutput(b *testing.B) {
 	} {
 		input := bytes.Repeat([]byte("go tool diagnostic output\n"), (testCase.size+25)/26)
 		input = input[:testCase.size]
-		b.Run(testCase.name+"/discard-forwarding", func(b *testing.B) {
-			// Verify capture and forwarding for this workload outside the measurement.
-			var forwarded bytes.Buffer
-			verification := &combinedWriter{output: &forwarded}
-			for offset := 0; offset < len(input); offset += testCase.chunkSize {
-				chunk := input[offset:min(offset+testCase.chunkSize, len(input))]
-				if written, err := verification.Write(chunk); err != nil || written != len(chunk) {
-					b.Fatalf("verify output write = %d, err %v; want %d bytes", written, err, len(chunk))
-				}
-			}
-			if !bytes.Equal(verification.take(), input) || !bytes.Equal(forwarded.Bytes(), input) {
-				b.Fatal("captured and forwarded output must equal the complete input")
-			}
-			b.ReportAllocs()
-			b.SetBytes(int64(len(input)))
-			b.ResetTimer()
-			b.ReportMetric(float64(len(input)), "bytes/op")
-			for i := 0; i < b.N; i++ {
-				writer := &combinedWriter{output: io.Discard}
+		for _, mode := range []struct {
+			name string
+			mode captureMode
+		}{{"full", captureFull}, {"status", captureStatus}} {
+			b.Run(testCase.name+"/"+mode.name, func(b *testing.B) {
+				// Verify capture and forwarding for this workload outside the measurement.
+				var forwarded bytes.Buffer
+				verification := &combinedWriter{output: &forwarded, mode: mode.mode}
 				for offset := 0; offset < len(input); offset += testCase.chunkSize {
 					chunk := input[offset:min(offset+testCase.chunkSize, len(input))]
-					if written, err := writer.Write(chunk); err != nil || written != len(chunk) {
-						b.Fatalf("write captured output = %d, err %v; want %d bytes", written, err, len(chunk))
+					if written, err := verification.Write(chunk); err != nil || written != len(chunk) {
+						b.Fatalf("verify output write = %d, err %v; want %d bytes", written, err, len(chunk))
 					}
 				}
-				captured := writer.take()
-				if len(captured) != len(input) {
-					b.Fatalf("captured output = %d bytes, want %d", len(captured), len(input))
+				want := input
+				if mode.mode == captureStatus && len(want) > statusDiagnosticLimit {
+					want = want[len(want)-statusDiagnosticLimit:]
 				}
-			}
-		})
+				if !bytes.Equal(verification.take(), want) || !bytes.Equal(forwarded.Bytes(), input) {
+					b.Fatal("captured output or forwarding did not match the selected mode")
+				}
+				b.ReportAllocs()
+				b.SetBytes(int64(len(input)))
+				b.ResetTimer()
+				b.ReportMetric(float64(len(input)), "bytes/op")
+				for i := 0; i < b.N; i++ {
+					writer := &combinedWriter{output: io.Discard, mode: mode.mode}
+					for offset := 0; offset < len(input); offset += testCase.chunkSize {
+						chunk := input[offset:min(offset+testCase.chunkSize, len(input))]
+						if written, err := writer.Write(chunk); err != nil || written != len(chunk) {
+							b.Fatalf("write captured output = %d, err %v; want %d bytes", written, err, len(chunk))
+						}
+					}
+					captured := writer.take()
+					if len(captured) != len(want) {
+						b.Fatalf("captured output = %d bytes, want %d", len(captured), len(want))
+					}
+				}
+			})
+		}
 	}
 }