Fix import declaration comments (#1030)

* Add handleImportDeclarationComments function.

* Fix indent.

* Update test cases accordingly.

* Implement better heuristic for adding comments.

* Make the test case more exhaustive.

src/comments.js

@@ -164,7 +164,8 @@ function attach(comments, ast, text, options) {
           followingNode,
           comment
         ) ||
-        handleOnlyComments(enclosingNode, ast, comment, isLastComment)
+        handleOnlyComments(enclosingNode, ast, comment, isLastComment) ||
+        handleImportDeclarationComments(enclosingNode, precedingNode, comment)
       ) {
         // We're good
       } else if (followingNode) {
@@ -646,6 +647,18 @@ function handleForComments(enclosingNode, precedingNode, comment) {
   return false;
 }
 
+function handleImportDeclarationComments(enclosingNode, precedingNode, comment) {
+  if (
+    precedingNode &&
+    enclosingNode && enclosingNode.type === "ImportDeclaration" &&
+    comment.type !== "CommentBlock" && comment.type !== "Block"
+  ) {
+    addTrailingComment(precedingNode, comment);
+    return true;
+  }
+  return false;
+}
+
 function printComment(commentPath) {
   const comment = commentPath.getValue();
   comment.printed = true;

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

@@ -131,6 +131,16 @@ import {
   a as //comment3 //comment2 //comment1
   b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import {
   //comment1
@@ -156,6 +166,16 @@ import {
   //comment3 //comment2 //comment1
   a as b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 "
 `;
 
@@ -182,6 +202,16 @@ import {
   a as //comment3 //comment2 //comment1
   b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import {
   //comment1
@@ -207,6 +237,16 @@ import {
   //comment3 //comment2 //comment1
   a as b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 "
 `;
 
@@ -233,6 +273,16 @@ import {
   a as //comment3 //comment2 //comment1
   b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import {
   //comment1
@@ -258,6 +308,16 @@ import {
   //comment3 //comment2 //comment1
   a as b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 "
 `;
 
@@ -284,6 +344,16 @@ import {
   a as //comment3 //comment2 //comment1
   b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import {
   //comment1
@@ -309,6 +379,16 @@ import {
   //comment3 //comment2 //comment1
   a as b
 } from \\"\\";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from \\"./module\\";
 "
 `;
 

tests/import/comments.js

@@ -20,3 +20,13 @@ import {
   a as //comment3 //comment2 //comment1
   b
 } from "";
+
+import {
+  // comment 1
+  FN1, // comment 2
+  /* comment 3 */ FN2,
+  // FN3,
+  FN4 /* comment 4 */
+  // FN4,
+  // FN5
+} from "./module";