From 03a13d6330843ad01eb66047e28700b82834d4ae Mon Sep 17 00:00:00 2001
From: Owen Voke <development@voke.dev>
Date: Mon, 9 Nov 2026 11:09:50 +0000
Subject: [PATCH] Blink: keep whitespace-only lines in `NoTrailingWhitespace`

PHP-CS-Fixer trims a whitespace token only up to its first line break: the
segments after it are pure whitespace, and it only rewrites a segment when
trimming leaves something behind. A line holding nothing but spaces is
therefore left alone, as is a trailing single-line run unless it ends the
file. The Go port stripped every run before a newline, so it emptied those
lines and reported files the PHP engine passes.

Trim the same span PHP does, including its open-tag exception, and treat
`\r\n` and a lone `\r` as line breaks as `\R` does.
---
 .../fixer/rules/no_trailing_whitespace.go     | 78 +++++--------------
 blink/internal/fixer/rules/rules_test.go      | 17 ++++
 2 files changed, 36 insertions(+), 59 deletions(-)

diff --git a/blink/internal/fixer/rules/no_trailing_whitespace.go b/blink/internal/fixer/rules/no_trailing_whitespace.go
index 5d0995142a..49c3ba8d6e 100644
--- a/blink/internal/fixer/rules/no_trailing_whitespace.go
+++ b/blink/internal/fixer/rules/no_trailing_whitespace.go
@@ -1,13 +1,18 @@
 package rules
 
 import (
+	"strings"
+
 	"github.com/ecsphp/ecs-src/blink/internal/token"
 	"github.com/ecsphp/ecs-src/blink/internal/tokens"
 )
 
 // PHP-CS-Fixer: https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/blob/master/src/Fixer/Whitespace/NoTrailingWhitespaceFixer.php
 //
-// NoTrailingWhitespace removes spaces and tabs at the end of a line.
+// NoTrailingWhitespace removes spaces and tabs at the end of a line. Like
+// PHP-CS-Fixer, it trims a whitespace token only up to its first line break,
+// so a line holding nothing but whitespace is left alone, and the same goes for
+// a single-line token unless it is the file's last.
 type NoTrailingWhitespace struct{}
 
 func (NoTrailingWhitespace) Name() string {
@@ -26,66 +31,21 @@ func (NoTrailingWhitespace) Fix(s *tokens.Stream) bool {
 		if t.Kind != token.Whitespace {
 			continue
 		}
-		v := stripTrailingWS(t.Value, i == last)
-		if v != t.Value {
-			s.SetValue(i, v)
-			changed = true
+		head, rest := t.Value, ""
+		if nl := strings.IndexAny(t.Value, "\r\n"); nl >= 0 {
+			head, rest = t.Value[:nl], t.Value[nl:]
+		} else if i != last {
+			continue
 		}
-	}
-	return changed
-}
-
-// stripTrailingWS drops a run of spaces/tabs that sits immediately before a
-// (\r?\n) newline, and - only in the file's final token (isLast) - a run at the
-// very end. It returns the input unchanged, with no allocation, when there is
-// nothing to strip, matching the previous regexes `[ \t]+(\r?\n)` and `[ \t]+$`.
-func stripTrailingWS(val string, isLast bool) string {
-	for i := 0; i < len(val); {
-		if val[i] == ' ' || val[i] == '\t' {
-			start := i
-			for i < len(val) && (val[i] == ' ' || val[i] == '\t') {
-				i++
-			}
-			if trailing(val, i, isLast) {
-				return stripTrailingBuild(val, start, isLast)
-			}
-		} else {
-			i++
+		// an open tag that already ends the line leaves this token's head as
+		// the next line's indentation
+		if i > 0 && s.At(i-1).Kind == token.OpenTag && strings.HasSuffix(s.At(i-1).Value, "\n") {
+			continue
 		}
-	}
-	return val
-}
-
-// stripTrailingBuild builds the stripped string once a first run to drop is
-// found at firstDrop, copying the untouched prefix and continuing the scan.
-func stripTrailingBuild(val string, firstDrop int, isLast bool) string {
-	out := make([]byte, 0, len(val))
-	out = append(out, val[:firstDrop]...)
-	for i := firstDrop; i < len(val); {
-		if val[i] == ' ' || val[i] == '\t' {
-			start := i
-			for i < len(val) && (val[i] == ' ' || val[i] == '\t') {
-				i++
-			}
-			if !trailing(val, i, isLast) {
-				out = append(out, val[start:i]...)
-			}
-		} else {
-			out = append(out, val[i])
-			i++
+		if trimmed := strings.TrimRight(head, " \t"); trimmed != head {
+			s.SetValue(i, trimmed+rest)
+			changed = true
 		}
 	}
-	return string(out)
-}
-
-// trailing reports whether a space/tab run ending at end should be dropped: it
-// is directly before a newline, or at the file's end in the final token.
-func trailing(val string, end int, isLast bool) bool {
-	if end < len(val) && val[end] == '\n' {
-		return true
-	}
-	if end+1 < len(val) && val[end] == '\r' && val[end+1] == '\n' {
-		return true
-	}
-	return end == len(val) && isLast
+	return changed
 }
diff --git a/blink/internal/fixer/rules/rules_test.go b/blink/internal/fixer/rules/rules_test.go
index 47f132e5bf..bcf00a0f5c 100644
--- a/blink/internal/fixer/rules/rules_test.go
+++ b/blink/internal/fixer/rules/rules_test.go
@@ -535,6 +535,23 @@ func TestNoTrailingWhitespace(t *testing.T) {
 	if _, changed := apply(t, NoTrailingWhitespace{}, "<?php $x = 1;\n"); changed {
 		t.Fatal("clean input should not change")
 	}
+	// as in PHP-CS-Fixer: only the part before a token's first line break is
+	// trimmed, so whitespace-only lines and the next line's indent stay
+	src := "<?php\nfunction f()\n{\n    $a = 1; \n        \n    $b = 2;\n}\n"
+	got, changed = apply(t, NoTrailingWhitespace{}, src)
+	if want := "<?php\nfunction f()\n{\n    $a = 1;\n        \n    $b = 2;\n}\n"; !changed || got != want {
+		t.Fatalf("blank line: changed=%v got=%q want=%q", changed, got, want)
+	}
+	// a single-line run is trimmed only at the end of the file
+	got, changed = apply(t, NoTrailingWhitespace{}, "<?php $x = 1;  ")
+	if want := "<?php $x = 1;"; !changed || got != want {
+		t.Fatalf("eof: changed=%v got=%q want=%q", changed, got, want)
+	}
+	// \r\n and a lone \r count as line breaks
+	got, changed = apply(t, NoTrailingWhitespace{}, "<?php $x = 1; \r\n$y = 2;\t\r$z = 3;\n")
+	if want := "<?php $x = 1;\r\n$y = 2;\r$z = 3;\n"; !changed || got != want {
+		t.Fatalf("crlf: changed=%v got=%q want=%q", changed, got, want)
+	}
 }
 
 func TestSingleBlankLineAtEndOfFile(t *testing.T) {