grep: let dot match newline in null-data mode

src/matcher.rs

@@ -285,6 +285,12 @@ impl CompiledPattern {
         if config.ignore_case {
             options |= RegexOptions::REGEX_OPTION_IGNORECASE;
         }
+        // In GNU grep's Basic/Extended modes, `-z` makes newline ordinary data
+        // for `.`, but PCRE keeps its existing non-DOTALL behavior. The GNU
+        // `pcre-context` test documents this as current behavior until PCRE2.
+        if config.null_data && matches!(config.regex_mode, RegexMode::Basic | RegexMode::Extended) {
+            options |= RegexOptions::REGEX_OPTION_MULTILINE;
+        }
 
         fn compile_with(pattern: &str, syntax: &Syntax, options: RegexOptions) -> UResult<Regex> {
             Regex::with_options_and_encoding(pattern, options, syntax).map_err(|err| {

tests/test_grep.rs

@@ -1251,6 +1251,27 @@ fn null_data_mode_records() {
         .succeeds()
         .stdout_is_bytes(b"hello\0");
 
+    // With NUL-delimited records, newline is ordinary data and `.` matches it.
+    let (_s, mut c) = ucmd();
+    c.args(&["-z", "-o", "."])
+        .pipe_in(&b"a\nb"[..])
+        .succeeds()
+        .stdout_is_bytes(b"a\0\n\0b\0");
+
+    // GNU grep's PCRE path currently does not let `.*` consume the extra
+    // newline here under -z; this mirrors the GNU pcre-context test.
+    let (_s, mut c) = ucmd();
+    c.args(&["-P", "-z", "-o", r"(?<=\n\n\n).*"])
+        .pipe_in(
+            &b"NUL preceded by 0 empty lines.\0\
+              \nNUL preceded by 1 empty line.\0\
+              \n\nNUL preceded by 2 empty lines.\0\
+              \n\n\nNUL preceded by 3 empty lines.\0\
+              \n\n\n\nNUL preceded by 4 empty lines.\0\n"[..],
+        )
+        .succeeds()
+        .stdout_is_bytes(b"NUL preceded by 3 empty lines.\0NUL preceded by 4 empty lines.\0");
+
     // Counting works under -z.
     let (_s, mut c) = ucmd();
     c.args(&["-z", "-c", "hello"])