fix: package.main with -- arguments

lib/config/load.js

@@ -74,7 +74,9 @@ function load(settings, options, config, callback) {
           }
           // if the script is found as a result of not being on the command
           // line, then we move any of the pre double-dash args in execArgs
-          const n = options.scriptPosition || options.args.length;
+          const n = options.scriptPosition === null ?
+            options.args.length : options.scriptPosition;
+
           options.execArgs = (options.execArgs || [])
             .concat(options.args.splice(0, n));
           options.scriptPosition = null;

lib/monitor/run.js

@@ -97,6 +97,8 @@ function run(options) {
     utils.version.major > 4 // only fork if node version > 4
 
   if (shouldFork) {
+    // this assumes the first argument is the script and slices it out, since
+    // we're forking
     var forkArgs = cmd.args.slice(1);
     var env = utils.merge(options.execOptions.env, process.env);
     stdio.push('ipc');

lib/monitor/watch.js

@@ -177,7 +177,7 @@ function filterAndRestart(files) {
 
     // if there's no matches, then test to see if the changed file is the
     // running script, if so, let's allow a restart
-    if (config.options.execOptions.script) {
+    if (config.options.execOptions && config.options.execOptions.script) {
       const script = path.resolve(config.options.execOptions.script);
       if (matched.result.length === 0 && script) {
         const length = script.length;

test/config/load.test.js

@@ -298,4 +298,27 @@ describe('config load', function () {
       done();
     })
   });
+
+  it('should support pkg.main and keep user args on args', done => {
+    process.chdir(path.resolve(pwd, 'test/fixtures/packages/main-and-start'));
+    const settings = { scriptPosition: 0, script: null, args: [ 'first', 'second' ] };
+    const options = { ignore: [], watch: [], monitor: [] };
+    const config = {
+      run: false,
+      system: { cwd: '/Users/remy/dev/nodemon/issues/1758' },
+      required: false,
+      dirs: [],
+      timeout: 1000,
+      options: { ignore: [], watch: [], monitor: [] },
+      lastStarted: 0,
+      loaded: []
+    }
+
+    load(settings, options, config, res => {
+      assert.deepEqual(res.execOptions.args, ['first', 'second']);
+      done();
+    })
+  });
+
+
 });

test/fixtures/packages/main-and-start/package.json

@@ -0,0 +1,6 @@
+{
+  "main": "./index.js",
+  "scripts": {
+    "start": "node index.js"
+  }
+}