fix: Exit 1 with no output if no match (#900) (#901)

When we can read all files, but none match, exit 1 and return no output. This
matches the behavior of grep more closely.

Fixes #900

src/grep.js

@@ -68,6 +68,10 @@ function _grep(options, regex, files) {
     }
   });
 
+  if (grep.length === 0 && common.state.errorCode !== 2) {
+    // We didn't hit the error above, but pattern didn't match
+    common.error('', { silent: true });
+  }
   return grep.join('\n') + '\n';
 }
 module.exports = _grep;

test/grep.js

@@ -49,6 +49,13 @@ test('if at least one file is missing, this should be an error', t => {
   t.is(result.code, 2);
 });
 
+test("multiple files, one doesn't exist, one doesn't match", t => {
+  const result = shell.grep(/oogabooga/, 'test/resources/file1.txt',
+    'test/resources/filedoesnotexist.txt');
+  t.truthy(shell.error());
+  t.is(result.code, 2);
+});
+
 //
 // Valids
 //
@@ -127,6 +134,17 @@ test('one file, * in string-regex, make sure * is not globbed', t => {
   t.is(result.toString(), 'this line ends in.js\nlllllllllllllllll.js\n');
 });
 
+test("one file, pattern doesn't match", t => {
+  const result = shell.grep('notfoundstring', 'test/resources/grep/file');
+  t.truthy(shell.error());
+  t.is(result.toString(), '');
+  t.is(result.stdout, '');
+  // TODO(#900): "grep: " isn't really the correct stderr output, but we need a
+  // non-empty string so `shell.error()` is truthy.
+  t.is(result.stderr, 'grep: ');
+  t.is(result.code, 1);
+});
+
 test('-l option', t => {
   const result = shell.grep('-l', 'test1', 'test/resources/file1', 'test/resources/file2',
     'test/resources/file1.txt');