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Leave trailing comments after handling a possible trailing com… (#10445)

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* Leave trailing comments aftre handling a possible trailing comma

* perf
This commit is contained in:
Nicolò Ribaudo
2019-09-23 19:14:43 +02:00
committed by GitHub
parent 962015f7e7
commit 3069747a81
5 changed files with 507 additions and 10 deletions
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41
packages/babel-parser/src/parser/comments.js
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@@ -38,7 +38,19 @@ export default class CommentsParser extends BaseParser {
this.state.leadingComments.push(comment);
}
adjustCommentsAfterTrailingComma(node: Node, elements: Node[]) {
adjustCommentsAfterTrailingComma(
node: Node,
elements: Node[],
// 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;
}
@@ -59,10 +71,16 @@ export default class CommentsParser extends BaseParser {
}
const newTrailingComments = [];
while (this.state.leadingComments.length) {
const leadingComment = this.state.leadingComments.shift();
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 = [];
@@ -70,6 +88,7 @@ export default class CommentsParser extends BaseParser {
node.trailingComments.push(leadingComment);
}
}
if (takeAllComments) this.state.leadingComments = [];
if (newTrailingComments.length > 0) {
lastElement.trailingComments = newTrailingComments;
@@ -130,16 +149,20 @@ export default class CommentsParser extends BaseParser {
if (firstChild) {
switch (node.type) {
case "ObjectExpression":
case "ObjectPattern":
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":
case "ArrayPattern":
this.adjustCommentsAfterTrailingComma(node, node.elements);
break;
case "ArrayPattern":
this.adjustCommentsAfterTrailingComma(node, node.elements, true);
break;
}
} else if (
this.state.commentPreviousNode &&
@@ -148,9 +171,11 @@ export default class CommentsParser extends BaseParser {
(this.state.commentPreviousNode.type === "ExportSpecifier" &&
node.type !== "ExportSpecifier"))
) {
this.adjustCommentsAfterTrailingComma(node, [
this.state.commentPreviousNode,
]);
this.adjustCommentsAfterTrailingComma(
node,
[this.state.commentPreviousNode],
true,
);
}
if (lastChild) {