fix: print usage menu for an unknown flag (#130)

When an unknown option was present it would only print a single-line error message stating that the flag was unknwon. Now it also prints the usage menu. This was done by overriding the `commander` code for unknown options handling.

package.json

@@ -32,6 +32,7 @@
     "pad": "^2.2.1",
     "require-all": "^3.0.0",
     "semver": "^5.5.1",
+    "sinon": "^8.1.1",
     "update-notifier": "^2.5.0",
     "validator": "^11.0.0",
     "yaml-js": "^0.2.3"

src/cli-validator/index.js

@@ -6,7 +6,7 @@
 require('./utils/checkVersion')('8.9.0');
 require('./utils/updateNotifier');
 
-const program = require('commander');
+const program = require('./utils/modified-commander');
 const cliValidator = require('./runValidator');
 const version = require('../../package.json').version;
 

src/cli-validator/utils/modified-commander.js

@@ -0,0 +1,23 @@
+const program = require('commander');
+
+// This module is used to modify the commander code. When
+// an unsupported option is given, only a single-line error
+// is printed. Now, it will also print out the usage menu.
+
+// deletes the function in order to reimplement it
+delete program['unknownOption'];
+
+// reimplementing the funciton
+program.unknownOption = function(flag) {
+  if (this._allowUnknownOption) return;
+  console.error();
+  console.error("  error: unknown option `%s'", flag);
+  console.error();
+
+  // this is the extra code added to the function
+  this.outputHelp();
+
+  process.exit(1);
+};
+
+module.exports = program;

test/cli-validator/tests/optionHandling.js

@@ -2,6 +2,8 @@ const intercept = require('intercept-stdout');
 const expect = require('expect');
 const stripAnsiFrom = require('strip-ansi');
 const commandLineValidator = require('../../../src/cli-validator/runValidator');
+const modifiedCommander = require('../../../src/cli-validator/utils/modified-commander');
+const sinon = require('sinon');
 
 // for an explanation of the text interceptor,
 // see the comments for the first test in expectedOutput.js
@@ -316,4 +318,21 @@ describe('cli tool - test option handling', function() {
     expect(warningCount).toEqual(3); // without the config this value is 5
     expect(errorCount).toEqual(3); // without the config this value is 0
   });
+
+  it('should return an error and usage menu when there is an unknown option', async function() {
+    const errorStub = sinon.stub(console, 'error');
+    const helpStub = sinon.stub(modifiedCommander, 'outputHelp');
+    const exitStub = sinon.stub(process, 'exit');
+
+    modifiedCommander.unknownOption('r');
+
+    expect(errorStub.called).toEqual(true);
+    expect(errorStub.secondCall.args[0].trim()).toEqual(
+      "error: unknown option `%s'"
+    );
+    expect(errorStub.secondCall.args[1].trim()).toEqual('r');
+    expect(helpStub.called).toEqual(true);
+    expect(exitStub.called).toEqual(true);
+    expect(exitStub.firstCall.args[0]).toEqual(1);
+  });
 });