Refactor trailing comment adjustment

Following up from babel#10369

- Unify the logic for adjusting trailing comments into a separate
  function
- Use it for all three cases, which fixes a bug for ObjectExpressions
  and CallExpressions
- Update tests to check for the fixed bug

packages/babel-parser/src/parser/comments.js

@@ -38,6 +38,42 @@ export default class CommentsParser extends BaseParser {
     this.state.leadingComments.push(comment);
   }
 
+  adjustCommentsAfterTrailingComma_(node: Node, elements: Node[]) {
+    if (elements.length === 0) {
+      return;
+    }
+    if (this.state.leadingComments.length === 0) {
+      return;
+    }
+    if (!this.state.commentPreviousNode) {
+      return;
+    }
+
+    const lastElement = last(elements);
+
+    for (let j = 0; j < this.state.leadingComments.length; j++) {
+      if (
+        this.state.leadingComments[j].end < this.state.commentPreviousNode.end
+      ) {
+        this.state.leadingComments.splice(j, 1);
+        j--;
+      }
+    }
+
+    lastElement.trailingComments = [];
+    while (this.state.leadingComments.length) {
+      const leadingComment = this.state.leadingComments.shift();
+      if (leadingComment.end < node.end) {
+        lastElement.trailingComments.push(leadingComment);
+      } else {
+        if (node.trailingComments === undefined) {
+          node.trailingComments = [];
+        }
+        node.trailingComments.push(leadingComment);
+      }
+    }
+  }
+
   processComment(node: Node): void {
     if (node.type === "Program" && node.body.length > 0) return;
 
@@ -84,85 +120,20 @@ export default class CommentsParser extends BaseParser {
 
     if (!lastChild && firstChild) lastChild = firstChild;
 
-    // Attach comments that follow a trailing comma on the last
-    // property in an object literal or a trailing comma in function arguments
-    // or a trailing comma in array expressions as trailing comments
-    if (firstChild && this.state.leadingComments.length > 0) {
-      const lastComment = last(this.state.leadingComments);
-
-      if (firstChild.type === "ObjectProperty") {
-        if (lastComment.start >= node.start && lastComment.end <= node.end) {
-          if (this.state.commentPreviousNode) {
-            for (j = 0; j < this.state.leadingComments.length; j++) {
-              if (
-                this.state.leadingComments[j].end <
-                this.state.commentPreviousNode.end
-              ) {
-                this.state.leadingComments.splice(j, 1);
-                j--;
-              }
-            }
-
-            if (this.state.leadingComments.length > 0) {
-              firstChild.trailingComments = this.state.leadingComments;
-              this.state.leadingComments = [];
-            }
-          }
-        }
-      } else if (
-        node.type === "CallExpression" &&
-        node.arguments &&
-        node.arguments.length
-      ) {
-        const lastArg = last(node.arguments);
-
-        if (
-          lastArg &&
-          lastComment.start >= lastArg.start &&
-          lastComment.end <= node.end
-        ) {
-          if (this.state.commentPreviousNode) {
-            for (j = 0; j < this.state.leadingComments.length; j++) {
-              if (
-                this.state.leadingComments[j].end <
-                this.state.commentPreviousNode.end
-              ) {
-                this.state.leadingComments.splice(j, 1);
-                j--;
-              }
-            }
-            if (this.state.leadingComments.length > 0) {
-              lastArg.trailingComments = this.state.leadingComments;
-              this.state.leadingComments = [];
-            }
-          }
-        }
-      } else if (node.type === "ArrayExpression" && node.elements.length > 0) {
-        if (this.state.commentPreviousNode) {
-          for (j = 0; j < this.state.leadingComments.length; j++) {
-            if (
-              this.state.leadingComments[j].end <
-              this.state.commentPreviousNode.end
-            ) {
-              this.state.leadingComments.splice(j, 1);
-              j--;
-            }
-          }
-
-          const lastElement = last(node.elements);
-          lastElement.trailingComments = [];
-          while (this.state.leadingComments.length) {
-            const leadingComment = this.state.leadingComments.shift();
-            if (leadingComment.end < node.end) {
-              lastElement.trailingComments.push(leadingComment);
-            } else {
-              if (node.trailingComments === undefined) {
-                node.trailingComments = [];
-              }
-              node.trailingComments.push(leadingComment);
-            }
-          }
-        }
+    // Adjust comments that follow a trailing comma on the last element in a
+    // comma separated list of nodes to be the trailing comments on the last
+    // element
+    if (firstChild) {
+      switch (node.type) {
+        case "ObjectExpression":
+          this.adjustCommentsAfterTrailingComma_(node, node.properties);
+          break;
+        case "CallExpression":
+          this.adjustCommentsAfterTrailingComma_(node, node.arguments);
+          break;
+        case "ArrayExpression":
+          this.adjustCommentsAfterTrailingComma_(node, node.elements);
+          break;
       }
     }
 

packages/babel-parser/test/fixtures/comments/basic/function-trailing-comma-shorthand/input.js

@@ -1 +1 @@
-fn(a, { b }, /* comment */);
+fn(a, { b }, /* comment 1 */) /* comment 2 */;

packages/babel-parser/test/fixtures/comments/basic/function-trailing-comma-shorthand/output.json

@@ -1,29 +1,29 @@
 {
   "type": "File",
   "start": 0,
-  "end": 28,
+  "end": 46,
   "loc": {
     "start": {
       "line": 1,
       "column": 0
     },
     "end": {
       "line": 1,
-      "column": 28
+      "column": 46
     }
   },
   "program": {
     "type": "Program",
     "start": 0,
-    "end": 28,
+    "end": 46,
     "loc": {
       "start": {
         "line": 1,
         "column": 0
       },
       "end": {
         "line": 1,
-        "column": 28
+        "column": 46
       }
     },
     "sourceType": "script",
@@ -32,29 +32,29 @@
       {
         "type": "ExpressionStatement",
         "start": 0,
-        "end": 28,
+        "end": 46,
         "loc": {
           "start": {
             "line": 1,
             "column": 0
           },
           "end": {
             "line": 1,
-            "column": 28
+            "column": 46
           }
         },
         "expression": {
           "type": "CallExpression",
           "start": 0,
-          "end": 27,
+          "end": 29,
           "loc": {
             "start": {
               "line": 1,
               "column": 0
             },
             "end": {
               "line": 1,
-              "column": 27
+              "column": 29
             }
           },
           "callee": {
@@ -166,22 +166,40 @@
               "trailingComments": [
                 {
                   "type": "CommentBlock",
-                  "value": " comment ",
+                  "value": " comment 1 ",
                   "start": 13,
-                  "end": 26,
+                  "end": 28,
                   "loc": {
                     "start": {
                       "line": 1,
                       "column": 13
                     },
                     "end": {
                       "line": 1,
-                      "column": 26
+                      "column": 28
                     }
                   }
                 }
               ]
             }
+          ],
+          "trailingComments": [
+            {
+              "type": "CommentBlock",
+              "value": " comment 2 ",
+              "start": 30,
+              "end": 45,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 30
+                },
+                "end": {
+                  "line": 1,
+                  "column": 45
+                }
+              }
+            }
           ]
         }
       }
@@ -191,17 +209,33 @@
   "comments": [
     {
       "type": "CommentBlock",
-      "value": " comment ",
+      "value": " comment 1 ",
       "start": 13,
-      "end": 26,
+      "end": 28,
       "loc": {
         "start": {
           "line": 1,
           "column": 13
         },
         "end": {
           "line": 1,
-          "column": 26
+          "column": 28
+        }
+      }
+    },
+    {
+      "type": "CommentBlock",
+      "value": " comment 2 ",
+      "start": 30,
+      "end": 45,
+      "loc": {
+        "start": {
+          "line": 1,
+          "column": 30
+        },
+        "end": {
+          "line": 1,
+          "column": 45
         }
       }
     }

packages/babel-parser/test/fixtures/comments/basic/function-trailing-comma/input.js

@@ -1 +1 @@
-fn(a, b, /* comment */);
+fn(a, b, /* comment 1 */) /* comment 2*/;