From 715298ed233d2db48df15df5beec803dfc93043c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Balv=C3=ADn?= <opensource@petrbalvin.org>
Date: Wed, 7 Oct 2026 12:59:54 +0200
Subject: [PATCH] test(format): keep the expansion signature off the EOF
 comment newline

An unterminated block comment at the end of a file swallows the
formatter's mandatory final newline, an artifact the token view already
documents as layout; the preproc signature entry now trims it so the
invariant stays about tokens.  The triggering input joins the corpus.

Assisted-by: GLM 5.3
---
 format/format_test.go                                       | 6 +++++-
 .../fuzz/FuzzFormatExpansionRoundTrip/062b12d69fb9426b      | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 format/testdata/fuzz/FuzzFormatExpansionRoundTrip/062b12d69fb9426b

diff --git a/format/format_test.go b/format/format_test.go
index a94f56c..5f03cc5 100644
--- a/format/format_test.go
+++ b/format/format_test.go
@@ -491,7 +491,11 @@ func stmtSignature(f *ast.File) []string {
 		case *ast.Include:
 			out = append(out, "include "+d.Header.Text)
 		case *ast.Preproc:
-			out = append(out, "preproc "+d.Raw)
+			// An unterminated block comment at the end of the file swallows
+			// the formatter's mandatory final newline, exactly the artifact
+			// the token view documents as layout; trimming it keeps the
+			// signature about tokens, not about that newline.
+			out = append(out, "preproc "+strings.TrimRight(d.Raw, " \t\r\n"))
 		}
 	}
 	for _, s := range f.Orphans {
diff --git a/format/testdata/fuzz/FuzzFormatExpansionRoundTrip/062b12d69fb9426b b/format/testdata/fuzz/FuzzFormatExpansionRoundTrip/062b12d69fb9426b
new file mode 100644
index 0000000..7fb5b1f
--- /dev/null
+++ b/format/testdata/fuzz/FuzzFormatExpansionRoundTrip/062b12d69fb9426b
@@ -0,0 +1,2 @@
+go test fuzz v1
+string("#/*0")