improve CLI usability (#2016)

Report supported options upon invalid option syntax.

fixes #1883

1 files changed, 9 insertions, 0 deletions

diff --git a/test/mocha/cli.js b/test/mocha/cli.js
index 565b6069..4234f2fb 100644
--- a/test/mocha/cli.js
+++ b/test/mocha/cli.js
@@ -537,4 +537,13 @@ describe("bin/uglifyjs", function () {
             done();
         });
     });
+    it("Should print supported options on invalid option syntax", function(done) {
+        var command = uglifyjscmd + " test/input/comments/filter.js -b ascii-only";
+        exec(command, function (err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stdout, "");
+            assert.ok(/^Supported options:\n\{[^}]+}\nERROR: `ascii-only` is not a supported option/.test(stderr), stderr);
+            done();
+        });
+    });
 });