packages/babel-parser/src/parser/comments.js
// @flow
/**
* Based on the comment attachment algorithm used in espree and estraverse.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import BaseParser from "./base";
import type { Comment, Node } from "../types";
function last<T>(stack: $ReadOnlyArray<T>): T {
return stack[stack.length - 1];
}
export default class CommentsParser extends BaseParser {
addComment(comment: Comment): void {
if (this.filename) comment.loc.filename = this.filename;
this.state.trailingComments.push(comment);
this.state.leadingComments.push(comment);
}
adjustCommentsAfterTrailingComma(
node: 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
// var { x } /* cmt */ = { y }
// we don't want /* cmt */ to be attached to { y }.
// On the other hand, in
// fn(x) [new line] /* cmt */ [new line] y
// /* cmt */ is both a trailing comment of fn(x) and a leading comment of y
takeAllComments?: boolean,
) {
if (this.state.leadingComments.length === 0) {
return;
}
let lastElement = null;
let i = elements.length;
while (lastElement === null && i > 0) {
lastElement = elements[--i];
}
if (lastElement === null) {
return;
}
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--;
}
}
const newTrailingComments = [];
for (let i = 0; i < this.state.leadingComments.length; i++) {
const leadingComment = this.state.leadingComments[i];
if (leadingComment.end < node.end) {
newTrailingComments.push(leadingComment);
// Perf: we don't need to splice if we are going to reset the array anyway
if (!takeAllComments) {
this.state.leadingComments.splice(i, 1);
i--;
}
} else {
if (node.trailingComments === undefined) {
node.trailingComments = [];
}
node.trailingComments.push(leadingComment);
}
}
if (takeAllComments) this.state.leadingComments = [];
if (newTrailingComments.length > 0) {
lastElement.trailingComments = newTrailingComments;
} else if (lastElement.trailingComments !== undefined) {
lastElement.trailingComments = [];
}
}
processComment(node: Node): void {
if (node.type === "Program" && node.body.length > 0) return;
const stack = this.state.commentStack;
let firstChild, lastChild, trailingComments, i, j;
if (this.state.trailingComments.length > 0) {
// If the first comment in trailingComments comes after the
// current node, then we're good - all comments in the array will
// come after the node and so it's safe to add them as official
// trailingComments.
if (this.state.trailingComments[0].start >= node.end) {
trailingComments = this.state.trailingComments;
this.state.trailingComments = [];
} else {
// Otherwise, if the first comment doesn't come after the
// current node, that means we have a mix of leading and trailing
// comments in the array and that leadingComments contains the
// same items as trailingComments. Reset trailingComments to
// zero items and we'll handle this by evaluating leadingComments
// later.
this.state.trailingComments.length = 0;
}
} else if (stack.length > 0) {
const lastInStack = last(stack);
if (
lastInStack.trailingComments &&
lastInStack.trailingComments[0].start >= node.end
) {
trailingComments = lastInStack.trailingComments;
delete lastInStack.trailingComments;
}
}
// Eating the stack.
if (stack.length > 0 && last(stack).start >= node.start) {
firstChild = stack.pop();
}
while (stack.length > 0 && last(stack).start >= node.start) {
lastChild = stack.pop();
}
if (!lastChild && firstChild) lastChild = firstChild;
// 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 "ObjectPattern":
this.adjustCommentsAfterTrailingComma(node, node.properties, true);
break;
case "CallExpression":
this.adjustCommentsAfterTrailingComma(node, node.arguments);
break;
case "ArrayExpression":
this.adjustCommentsAfterTrailingComma(node, node.elements);
break;
case "ArrayPattern":
this.adjustCommentsAfterTrailingComma(node, node.elements, true);
break;
}
} else if (
this.state.commentPreviousNode &&
((this.state.commentPreviousNode.type === "ImportSpecifier" &&
node.type !== "ImportSpecifier") ||
(this.state.commentPreviousNode.type === "ExportSpecifier" &&
node.type !== "ExportSpecifier"))
) {
this.adjustCommentsAfterTrailingComma(node, [
this.state.commentPreviousNode,
]);
}
if (lastChild) {
if (lastChild.leadingComments) {
if (
lastChild !== node &&
lastChild.leadingComments.length > 0 &&
last(lastChild.leadingComments).end <= node.start
) {
node.leadingComments = lastChild.leadingComments;
delete lastChild.leadingComments;
} else {
// A leading comment for an anonymous class had been stolen by its first ClassMethod,
// so this takes back the leading comment.
// See also: https://github.com/eslint/espree/issues/158
for (i = lastChild.leadingComments.length - 2; i >= 0; --i) {
if (lastChild.leadingComments[i].end <= node.start) {
node.leadingComments = lastChild.leadingComments.splice(0, i + 1);
break;
}
}
}
}
} else if (this.state.leadingComments.length > 0) {
if (last(this.state.leadingComments).end <= node.start) {
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) {
node.leadingComments = this.state.leadingComments;
this.state.leadingComments = [];
}
} else {
// https://github.com/eslint/espree/issues/2
//
// In special cases, such as return (without a value) and
// debugger, all comments will end up as leadingComments and
// will otherwise be eliminated. This step runs when the
// commentStack is empty and there are comments left
// in leadingComments.
//
// This loop figures out the stopping point between the actual
// leading and trailing comments by finding the location of the
// first comment that comes after the given node.
for (i = 0; i < this.state.leadingComments.length; i++) {
if (this.state.leadingComments[i].end > node.start) {
break;
}
}
// Split the array based on the location of the first comment
// that comes after the node. Keep in mind that this could
// result in an empty array, and if so, the array must be
// deleted.
const leadingComments = this.state.leadingComments.slice(0, i);
if (leadingComments.length) {
node.leadingComments = leadingComments;
}
// Similarly, trailing comments are attached later. The variable
// must be reset to null if there are no trailing comments.
trailingComments = this.state.leadingComments.slice(i);
if (trailingComments.length === 0) {
trailingComments = null;
}
}
}
this.state.commentPreviousNode = node;
if (trailingComments) {
if (
trailingComments.length &&
trailingComments[0].start >= node.start &&
last(trailingComments).end <= node.end
) {
node.innerComments = trailingComments;
} else {
// TrailingComments maybe contain innerComments
const firstTrailingCommentIndex = trailingComments.findIndex(
comment => comment.end >= node.end,
);
if (firstTrailingCommentIndex > 0) {
node.innerComments = trailingComments.slice(
0,
firstTrailingCommentIndex,
);
node.trailingComments = trailingComments.slice(
firstTrailingCommentIndex,
);
} else {
node.trailingComments = trailingComments;
}
}
}
stack.push(node);
}
}