Support "// prettier-ignore" in comment blocks (#1125)

* // prettier-ignore has to be last comment

* Add test for #1109

src/printer.js

@@ -65,7 +65,7 @@ function genericPrint(path, options, printPath) {
   if (
     node.comments &&
     node.comments.length > 0 &&
-    node.comments[0].value.trim() === "prettier-ignore"
+    node.comments[node.comments.length - 1].value.trim() === "prettier-ignore"
   ) {
     return options.originalText.slice(util.locStart(node), util.locEnd(node));
   }

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

@@ -18,6 +18,14 @@ exports[`ignore.js 1`] = `
     0, 0, 0
   );
 
+  // Let's make sure that this comment doesn't interfere
+
+  // prettier-ignore
+  const commentsWithPrettierIgnore =   {
+    \\"ewww\\":
+            \\"gross-formatting\\",
+  };
+
   // prettier-ignore
   console.error(
     'In order to use ' + prompt + ', you need to configure a ' +
@@ -69,6 +77,14 @@ function a() {
     0, 0, 0
   );
 
+  // Let's make sure that this comment doesn't interfere
+
+  // prettier-ignore
+  const commentsWithPrettierIgnore =   {
+    \\"ewww\\":
+            \\"gross-formatting\\",
+  };
+
   // prettier-ignore
   console.error(
     'In order to use ' + prompt + ', you need to configure a ' +

tests/ignore/ignore.js

@@ -15,6 +15,14 @@ function a() {
     0, 0, 0
   );
 
+  // Let's make sure that this comment doesn't interfere
+
+  // prettier-ignore
+  const commentsWithPrettierIgnore =   {
+    "ewww":
+            "gross-formatting",
+  };
+
   // prettier-ignore
   console.error(
     'In order to use ' + prompt + ', you need to configure a ' +