[parser] Don't crash on comment after trailing comma after eli… (#10490)

babel · Sep 24, 2019 · 0e95026 · 0e95026
1 parent 26be14b
commit 0e95026
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Showing 3 changed files with 200 additions and 4 deletions.
diff --git a/packages/babel-parser/src/parser/comments.js b/packages/babel-parser/src/parser/comments.js
@@ -40,7 +40,7 @@ export default class CommentsParser extends BaseParser {
 
   adjustCommentsAfterTrailingComma(
     node: Node,
-    elements: Node[],
+    elements: (Node | null)[],
     // When the current node is followed by a token which hasn't a respective AST node, we
     // need to take all the trailing comments to prevent them from being attached to an
     // unrelated node. e.g. in
@@ -55,12 +55,15 @@ export default class CommentsParser extends BaseParser {
       return;
     }
 
-    if (elements.length === 0) {
+    let lastElement = null;
+    let i = elements.length;
+    while (lastElement === null && i > 0) {
+      lastElement = elements[--i];
+    }
+    if (lastElement === null) {
       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

diff --git a/packages/babel-parser/test/fixtures/comments/regression/10448/input.js b/packages/babel-parser/test/fixtures/comments/regression/10448/input.js
@@ -0,0 +1,2 @@
+function foo([foo, /* not used */, /* not used */]) {
+}
diff --git a/packages/babel-parser/test/fixtures/comments/regression/10448/output.json b/packages/babel-parser/test/fixtures/comments/regression/10448/output.json
@@ -0,0 +1,191 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 55,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 2,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 55,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 2,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "FunctionDeclaration",
+        "start": 0,
+        "end": 55,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 2,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 9,
+          "end": 12,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 9
+            },
+            "end": {
+              "line": 1,
+              "column": 12
+            },
+            "identifierName": "foo"
+          },
+          "name": "foo"
+        },
+        "generator": false,
+        "async": false,
+        "params": [
+          {
+            "type": "ArrayPattern",
+            "start": 13,
+            "end": 50,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 13
+              },
+              "end": {
+                "line": 1,
+                "column": 50
+              }
+            },
+            "elements": [
+              {
+                "type": "Identifier",
+                "start": 14,
+                "end": 17,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 17
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo",
+                "trailingComments": [
+                  {
+                    "type": "CommentBlock",
+                    "value": " not used ",
+                    "start": 19,
+                    "end": 33,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 19
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 33
+                      }
+                    }
+                  },
+                  {
+                    "type": "CommentBlock",
+                    "value": " not used ",
+                    "start": 35,
+                    "end": 49,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 35
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 49
+                      }
+                    }
+                  }
+                ]
+              },
+              null
+            ]
+          }
+        ],
+        "body": {
+          "type": "BlockStatement",
+          "start": 52,
+          "end": 55,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 52
+            },
+            "end": {
+              "line": 2,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  },
+  "comments": [
+    {
+      "type": "CommentBlock",
+      "value": " not used ",
+      "start": 19,
+      "end": 33,
+      "loc": {
+        "start": {
+          "line": 1,
+          "column": 19
+        },
+        "end": {
+          "line": 1,
+          "column": 33
+        }
+      }
+    },
+    {
+      "type": "CommentBlock",
+      "value": " not used ",
+      "start": 35,
+      "end": 49,
+      "loc": {
+        "start": {
+          "line": 1,
+          "column": 35
+        },
+        "end": {
+          "line": 1,
+          "column": 49
+        }
+      }
+    }
+  ]
+}