fix: middleware added multiple times due to reference bug (#1282)

lib/command.js

@@ -17,12 +17,11 @@ module.exports = function command (yargs, usage, validation, globalMiddleware) {
   let aliasMap = {}
   let defaultCommand
   globalMiddleware = globalMiddleware || []
-  self.addHandler = function addHandler (cmd, description, builder, handler, middlewares) {
+  self.addHandler = function addHandler (cmd, description, builder, handler, _middlewares) {
     let aliases = []
+    const middlewares = (_middlewares || []).slice(0)
     handler = handler || (() => {})
-    middlewares = middlewares || []
-    globalMiddleware.push(...middlewares)
-    middlewares = globalMiddleware
+
     if (Array.isArray(cmd)) {
       aliases = cmd.slice(1)
       cmd = cmd[0]
@@ -232,7 +231,7 @@ module.exports = function command (yargs, usage, validation, globalMiddleware) {
     if (commandHandler.handler && !yargs._hasOutput()) {
       yargs._setHasOutput()
 
-      const middlewares = commandHandler.middlewares || []
+      const middlewares = globalMiddleware.slice(0).concat(commandHandler.middlewares || [])
 
       innerArgv = applyMiddleware(innerArgv, middlewares)
 

test/middleware.js

@@ -140,4 +140,25 @@ describe('middleware', () => {
         .parse()
     })
   })
+
+  // see: https://github.com/yargs/yargs/issues/1281
+  it("doesn't modify globalMiddleware array when executing middleware", () => {
+    let count = 0
+    yargs('bar')
+      .middleware((argv) => {
+        count++
+      })
+      .command('foo', 'foo command', () => {}, () => {}, [
+        () => {
+          count++
+        }
+      ])
+      .command('bar', 'bar command', () => {}, () => {}, [
+        () => {
+          count++
+        }
+      ])
+      .parse()
+    count.should.equal(2)
+  })
 })