Always output comment newlines, fix edge case with function param output

src/comments.js

@@ -6,7 +6,7 @@ var isObject = types.builtInTypes.object;
 var pp = require("./pp");
 var fromString = pp.fromString;
 var concat = pp.concat;
-var line = pp.line;
+var hardline = pp.hardline;
 var util = require("./util");
 var comparePos = util.comparePos;
 var childNodesCacheKey = require("private").makeUniqueKey();
@@ -266,7 +266,7 @@ function printLeadingComment(commentPath, print) {
   if (comment.trailing) {
     // When we print trailing comments as leading comments, we don't
     // want to bring any trailing spaces along.
-    parts.push(line);
+    parts.push(hardline);
 
   }
 
@@ -288,7 +288,7 @@ function printLeadingComment(commentPath, print) {
 
   // }
   else {
-    parts.push(line);
+    parts.push(hardline);
   }
 
   return concat(parts);

src/printer.js

@@ -1740,7 +1740,6 @@ function printArgumentsList(path, options, print) {
     return "()";
   }
 
-  const shouldBreak = printed.slice(0, -1).some(hasHardLine);
   const lastArg = util.getLast(path.getValue().arguments);
   // This is just an optimization; I think we could return the
   // conditional group for all function calls, but it's more expensive
@@ -1748,9 +1747,12 @@ function printArgumentsList(path, options, print) {
   const groupLastArg = lastArg.type === "ObjectExpression" ||
         lastArg.type === "ArrayExpression" ||
         lastArg.type === "FunctionExpression" ||
-        lastArg.type === "ArrowFunctionExpression";
+        lastArg.type === "ArrowFunctionExpression" ||
+        lastArg.type === "CallExpression" ||
+        lastArg.type === "NewExpression";
 
   if (groupLastArg) {
+    const shouldBreak = printed.slice(0, -1).some(hasHardLine);
     return conditionalGroup(
       [
         concat([
@@ -1784,6 +1786,7 @@ function printArgumentsList(path, options, print) {
     );
   }
 
+  const shouldBreak = printed.some(hasHardLine);
   return group(
     concat([
       "(",

tests/node_tests/stream/__snapshots__/jsfmt.spec.js.snap

@@ -67,8 +67,8 @@ class MyWriteStream extends stream.Writable {}
 class MyDuplex extends stream.Duplex {}
 class MyTransform extends stream.Duplex {}
 
-new MyReadStream().pipe(new MyDuplex()).pipe(new MyTransform()).pipe(
-  new MyWriteStream()
-);
+new MyReadStream().pipe(
+  new MyDuplex()
+).pipe(new MyTransform()).pipe(new MyWriteStream());
 "
 `;

tests/promises/__snapshots__/jsfmt.spec.js.snap

@@ -438,8 +438,8 @@ new Promise((resolve, reject) => resolve(0)).then(function(num) {
 
 new Promise(function(resolve, reject) {
   resolve(new Promise(function(resolve, reject) {
-      resolve(0);
-    }));
+    resolve(0);
+  }));
 }).then(function(num) {
   var a: number = num;
   var b: string = num;
@@ -447,10 +447,10 @@ new Promise(function(resolve, reject) {
 
 new Promise(function(resolve, reject) {
   resolve(new Promise(function(resolve, reject) {
-      resolve(new Promise(function(resolve, reject) {
-          resolve(0);
-        }));
+    resolve(new Promise(function(resolve, reject) {
+      resolve(0);
     }));
+  }));
 }).then(function(num) {
   var a: number = num;
   var b: string = num;
@@ -481,8 +481,8 @@ new Promise(function(resolve, reject) {
 
 new Promise(function(resolve, reject) {
   reject(new Promise(function(resolve, reject) {
-      reject(0);
-    }));
+    reject(0);
+  }));
 }).catch(function(num) {
   var a: Promise<number> = num;
   var b: number = num;