grep: short-circuit inverted empty patterns

src/lib.rs

@@ -20,7 +20,7 @@ use clap::{Arg, ArgAction, Command};
 use std::ffi::{OsStr, OsString};
 use std::io::{IsTerminal as _, Read};
 use std::path::Path;
-use uucore::error::{FromIo, UResult, USimpleError};
+use uucore::error::{ExitCode, FromIo, UResult, USimpleError};
 
 #[derive(Clone, Copy, PartialEq, Eq)]
 #[doc(hidden)]
@@ -399,6 +399,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     };
 
     let matcher = Matcher::compile(&config)?;
+    // An empty pattern matches every line; with `-v`, GNU grep selects no lines
+    // and exits as "no match" without reading any input files.
+    if invert_match && patterns.iter().any(|pattern| pattern.is_empty()) {
+        return Err(ExitCode::new(1));
+    }
+
     let writer = OutputWriter::new(&config);
     let mut searcher = Searcher::new(&config, matcher, writer);
     let mut lb = LineBuffer::new(if config.null_data { b'\0' } else { b'\n' });

tests/test_grep.rs

@@ -374,6 +374,27 @@ fn empty_pattern_matches_every_line() {
         .stdout_only("a\nb\nc\n");
 }
 
+#[test]
+fn inverted_empty_pattern_short_circuits() {
+    let (_s, mut c) = ucmd();
+    c.args(&["-e", "", "-v", "-c"])
+        .pipe_in("a\nb\n")
+        .fails_with_code(1)
+        .no_output();
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-e", "", "-v", "-c", "missing"])
+        .fails_with_code(1)
+        .no_output();
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-e", "", "-e", "[", "-v"])
+        .pipe_in("a\n")
+        .fails_with_code(2)
+        .no_stdout()
+        .stderr_contains("invalid pattern");
+}
+
 #[test]
 fn pattern_starting_with_dash_needs_double_dash() {
     let (_s, mut c) = ucmd();