Fix an out-of-bounds array access when formatting some empty comment

mickael-carl · mickael-carl · commit 6d83c91d498a · 2025-03-06T23:48:39.000Z
diff --git a/formatter/testdata/empty_comment.fmt.golden b/formatter/testdata/empty_comment.fmt.golden
@@ -0,0 +1,2 @@
+//
+{}
diff --git a/formatter/testdata/empty_comment.jsonnet b/formatter/testdata/empty_comment.jsonnet
@@ -0,0 +1,2 @@
+#
+{}
diff --git a/internal/formatter/enforce_comment_style.go b/internal/formatter/enforce_comment_style.go
@@ -38,7 +38,7 @@ func (c *EnforceCommentStyle) FodderElement(p pass.ASTPass, element *ast.FodderE
 				*comment = "#" + (*comment)[2:]
 			}
 			if c.Options.CommentStyle == CommentStyleSlash && (*comment)[0] == '#' {
-				if !c.seenFirstFodder && (*comment)[1] == '!' {
+				if !c.seenFirstFodder && len(*comment) > 1 && (*comment)[1] == '!' {
 					return
 				}
 				*comment = "//" + (*comment)[1:]

Original file line number	Diff line number	Diff line change
`@@ -38,7 +38,7 @@ func (c EnforceCommentStyle) FodderElement(p pass.ASTPass, element ast.FodderE`
`38`	`38`	`comment = "#" + (comment)[2:]`
`39`	`39`	`}`
`40`	`40`	`if c.Options.CommentStyle == CommentStyleSlash && (*comment)[0] == '#' {`
`41`		`- if !c.seenFirstFodder && (*comment)[1] == '!' {`
	`41`	`+ if !c.seenFirstFodder && len(comment) > 1 && (comment)[1] == '!' {`
`42`	`42`	`return`
`43`	`43`	`}`
`44`	`44`	`comment = "//" + (comment)[1:]`