Implements a deprecation warning

Author: Maël Nison

src/cli/index.js

@@ -110,9 +110,14 @@ export function main({
     command = commands.run;
   }
 
+  let warnAboutRunDashDash = false;
   // we using "yarn <script> -abc" or "yarn run <script> -abc", we want -abc to be script options, not yarn options
   if (command === commands.run) {
-    args.unshift('--');
+    if (endArgs.length === 0) {
+      endArgs = ['--', ... args.splice(1, args.length)];
+    } else {
+      warnAboutRunDashDash = true;
+    }
   }
 
   command.setFlags(commander);
@@ -124,7 +129,7 @@ export function main({
     ...getRcArgs(commandName, args),
     ...args,
   ]);
-  commander.args = commander.args.concat(endArgs);
+  commander.args = commander.args.concat(endArgs.slice(1));
 
   // we strip cmd
   console.assert(commander.args.length >= 1);
@@ -176,6 +181,11 @@ export function main({
   //
   const run = (): Promise<void> => {
     invariant(command, 'missing command');
+
+    if (warnAboutRunDashDash) {
+      reporter.warn(reporter.lang('dashDashDeprecation'));
+    }
+
     return command.run(config, reporter, commander, commander.args).then(exitCode => {
       if (outputWrapper) {
         reporter.footer(false);
@@ -408,7 +418,7 @@ export default function start() {
   const doubleDashIndex = process.argv.findIndex(element => element === '--');
   const startArgs = process.argv.slice(0, 2);
   const args = process.argv.slice(2, doubleDashIndex === -1 ? process.argv.length : doubleDashIndex);
-  const endArgs = doubleDashIndex === -1 ? [] : process.argv.slice(doubleDashIndex + 1, process.argv.length);
+  const endArgs = doubleDashIndex === -1 ? [] : process.argv.slice(doubleDashIndex, process.argv.length);
 
   main({startArgs, args, endArgs});
 }

src/reporters/lang/en.js

@@ -188,6 +188,7 @@ const messages = {
 
   execMissingCommand: 'Missing command name.',
 
+  dashDashDeprecation: "Using -- to pass arguments to your scripts isn't required anymore. Doing this may cause issues in future versions.",
   commandNotSpecified: 'No command specified.',
   binCommands: 'Commands available from binary scripts: ',
   possibleCommands: 'Project commands',