Fix multiparser trailing comma regression (#3405)

* Fix multiparser trailing comma regression

* Refactor trailing comma application

src/multiparser.js

@@ -26,12 +26,11 @@ function printSubtree(path, print, options) {
 function parseAndPrint(text, partialNextOptions, parentOptions) {
   const nextOptions = Object.assign({}, parentOptions, partialNextOptions, {
     parentParser: parentOptions.parser,
-    trailingComma:
-      partialNextOptions.parser === "json"
-        ? "none"
-        : partialNextOptions.trailingComma,
     originalText: text
   });
+  if (nextOptions.parser === "json") {
+    nextOptions.trailingComma = "none";
+  }
   const ast = require("./parser").parse(text, nextOptions);
   const astComments = ast.comments;
   delete ast.comments;

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

@@ -0,0 +1,30 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`trailing-comma.md 1`] = `
+### Some heading
+
+\`\`\`js
+someFunctionCall(
+  foo,
+  bar,
+  foobar,
+  sometehingReallyLongAndHairy,
+  somethingElse,
+  breakNow,
+);
+\`\`\`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+### Some heading
+
+\`\`\`js
+someFunctionCall(
+  foo,
+  bar,
+  foobar,
+  sometehingReallyLongAndHairy,
+  somethingElse,
+  breakNow,
+);
+\`\`\`
+
+`;

tests/multiparser_markdown_js/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, ["markdown"], { trailingComma: "all" });

tests/multiparser_markdown_js/trailing-comma.md

@@ -0,0 +1,12 @@
+### Some heading
+
+```js
+someFunctionCall(
+  foo,
+  bar,
+  foobar,
+  sometehingReallyLongAndHairy,
+  somethingElse,
+  breakNow,
+);
+```