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Leave trailing comments after handling a possible trailing comma #10445

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merged 2 commits into from Sep 23, 2019
Merged

Leave trailing comments after handling a possible trailing comma #10445

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55f5c1c
Leave trailing comments aftre handling a possible trailing comma
nicolo-ribaudo Sep 16, 2019
4729994
perf
nicolo-ribaudo Sep 16, 2019
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37 changes: 29 additions & 8 deletions packages/babel-parser/src/parser/comments.js
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Expand Up @@ -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;
}
Expand All @@ -59,17 +71,20 @@ 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);
this.state.leadingComments.splice(i, 1);
i--;
} else {
if (node.trailingComments === undefined) {
node.trailingComments = [];
}
node.trailingComments.push(leadingComment);
}
}
if (takeAllComments) this.state.leadingComments.length = 0;
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nit: this.state.leadingComments = [] is more idiomatic and should be marginally faster than this.state.leadingComments.length = 0 by saving calls to StoreICTrampoline.
The former is compiled to

                  -- </Users/jh/code/babel/packages/babel-parser/lib/index.js:6266:14> --
0x1fafdfb87845   545  48b8a92cd4eaa8090000 REX.W movq rax,0x9a8ead42ca9    ;; object: 0x09a8ead42ca9 <Map(PACKED_ELEMENTS)>
0x1fafdfb8784f   54f  498947ff       REX.W movq [r15-0x1],rax
0x1fafdfb87853   553  498b9da0000000 REX.W movq rbx,[r13+0xa0] (root (empty_fixed_array))
0x1fafdfb8785a   55a  49895f07       REX.W movq [r15+0x7],rbx
0x1fafdfb8785e   55e  49895f0f       REX.W movq [r15+0xf],rbx
0x1fafdfb87862   562  49c7471700000000 REX.W movq [r15+0x17],0x0
                  -- </Users/jh/code/babel/packages/babel-parser/lib/index.js:6266:37> --
0x1fafdfb8786a   56a  4d89b9cf000000 REX.W movq [r9+0xcf],r15
0x1fafdfb87871   571  48c7c30000fcff REX.W movq rbx,0xfffc0000
0x1fafdfb87878   578  4923d9         REX.W andq rbx,r9
0x1fafdfb8787b   57b  f6430804       testb [rbx+0x8],0x4

The latter is compiled to

                  -- </Users/jh/code/babel/packages/babel-parser/lib/index.js:6268:44> --
0x1fafde852e4e   44e  33c0           xorl rax,rax
0x1fafde852e50   450  498b8d280a0000 REX.W movq rcx,[r13+0xa28] (root (length_string))
0x1fafde852e57   457  48bf000000002b000000 REX.W movq rdi,0x2b00000000
0x1fafde852e61   461  488b75e0       REX.W movq rsi,[rbp-0x20]
                  -- Inlined Trampoline to StoreICTrampoline --
0x1fafde852e65   465  49ba40fb6c0001000000 REX.W movq r10,0x1006cfb40  (StoreICTrampoline)
0x1fafde852e6f   46f  41ffd2         call r10
0x1fafdfb877aa   4aa  4c8b4518       REX.W movq r8,[rbp+0x18]
0x1fafdfb877ae   4ae  48b8a92cd4eaa8090000 REX.W movq rax,0x9a8ead42ca9    ;; object: 0x09a8ead42ca9 <Map(PACKED_ELEMENTS)>
0x1fafdfb877b8   4b8  49bce990a15ea8090000 REX.W movq r12,0x9a85ea190e9    ;; object: 0x09a85ea190e9 <Map(HOLEY_ELEMENTS)>
0x1fafdfb877c2   4c2  49bbf994a15ea8090000 REX.W movq r11,0x9a85ea194f9    ;; object: 0x09a85ea194f9 <Map(HOLEY_ELEMENTS)>

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Oh I thought that resetting the length was faster because it doesn't create a new array. Will update 👍


if (newTrailingComments.length > 0) {
lastElement.trailingComments = newTrailingComments;
Expand Down Expand Up @@ -130,16 +145,20 @@ 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 &&
Expand All @@ -148,9 +167,11 @@ 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) {
Expand Down
20 changes: 19 additions & 1 deletion ...s/babel-parser/test/fixtures/comments/basic/switch-function-call-no-semicolon/output.json
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Expand Up @@ -250,7 +250,25 @@
"label": null
}
],
"test": null
"test": null,
"leadingComments": [
{
"type": "CommentLine",
"value": " comment",
"start": 47,
"end": 57,
"loc": {
"start": {
"line": 4,
"column": 4
},
"end": {
"line": 4,
"column": 14
}
}
}
]
}
]
}
Expand Down
20 changes: 19 additions & 1 deletion packages/babel-parser/test/fixtures/comments/regression/10230/output.json
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Expand Up @@ -215,7 +215,25 @@
"identifierName": "B"
},
"name": "B"
}
},
"leadingComments": [
{
"type": "CommentLine",
"value": " Two",
"start": 27,
"end": 33,
"loc": {
"start": {
"line": 6,
"column": 0
},
"end": {
"line": 6,
"column": 6
}
}
}
]
}
],
"directives": []
Expand Down
5 changes: 5 additions & 0 deletions packages/babel-parser/test/fixtures/comments/regression/10432/input.js
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@@ -0,0 +1,5 @@
const socket = socketClient(address)
/* istanbul ignore next */
socket.on('connect', function () {
debug('Connected to ' + address)
})