Simplify mergeEmitNode #59613
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Simplify mergeEmitNode #59613
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typescript-bot
added
Author: Team
For Uncommitted Bug
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@typescript-bot perf test this faster |
jakebailey
commented
Aug 12, 2024
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| function mergeTokenSourceMapRanges(sourceRanges: (TextRange | undefined)[], destRanges: (TextRange | undefined)[]) { | ||
| if (!destRanges) destRanges = []; | ||
| for (const key in sourceRanges) { | ||
| destRanges[key] = sourceRanges[key]; | ||
| } | ||
| return destRanges; | ||
| } |
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I read this function and it sort of scared me; what if the test has more elements than the source? Then I replaced it and nothing changed, so I kept going...
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sourceRanges and destRanges are holey arrays, so length doesn't actually matter. It probably should just be a Map<number, TextRange>, to be honest.
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@jakebailey Here they are:
tscComparison Report - baseline..pr
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Developer Information: |
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A lot of the complexity in |
rbuckton
reviewed
Aug 13, 2024
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| function mergeTokenSourceMapRanges(sourceRanges: (TextRange | undefined)[], destRanges: (TextRange | undefined)[]) { | ||
| if (!destRanges) destRanges = []; | ||
| for (const key in sourceRanges) { | ||
| destRanges[key] = sourceRanges[key]; | ||
| } | ||
| return destRanges; | ||
| } |
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sourceRanges and destRanges are holey arrays, so length doesn't actually matter. It probably should just be a Map<number, TextRange>, to be honest.
| @@ -7449,13 +7446,13 @@ function mergeEmitNode(sourceEmitNode: EmitNode, destEmitNode: EmitNode | undefi | |||
| // `leadingComments` are concatenated with any existing leading comments on the destination | |||
| if (leadingComments) { | |||
| // We use `.slice()` in case `destEmitNode.leadingComments` is pushed to later | |||
| destEmitNode.leadingComments = addRange(leadingComments.slice(), destEmitNode.leadingComments); | |||
| destEmitNode.leadingComments = leadingComments.slice(); | |||
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I worry this results in a different inconsistency now. Before, we would attempt to merge the emit information for the old node into anything set on the new node prior to calling setOriginalNode. Now we will conditionally overwrite some properties but not others.
const oldNode = ...;
addSyntheticLeadingComment(oldNode, SyntaxKind.SingleLineCommentTrivia, "foo");
const newNode = ...;
addSyntheticLeadingComment(oldNode, SyntaxKind.SingleLineCommentTrivia, "bar");
addSyntheticTrailingComment(oldNode, SyntaxKind.SingleLineCommentTrivia, "baz");
setOriginalNode(newNode, oldNode);
// before
getSyntheticLeadingComments(newNode).length; // 2 (foo and bar)
getSyntheticTrailingComments(newNode).length; // 1 (baz)
// after
getSyntheticLeadingComments(newNode).length; // 1 (foo)
getSyntheticTrailingComments(newNode).length; // 1 (baz)After this change we end up with oldNode's leading comments but newNodes trailing comments, which seems more confusing.
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I certainly am not confident in this PR, but we do need something for #59332.
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I originally considered using appendIfUnique to avoid duplicating but also to concatenate. Would you think that's a good fix?
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The issue that drove this PR is not so much an issue with |
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I found the actual underlying problem in #59332 in |
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@armanio123 and I noticed in #59332 that simply copying
leadingComments/trailingCommentsand force overwriting (rather than concatenating) fixes the comment duplication problem from #59332.Reading things further, it the function already force copies over the other node's information (flags, comment ranges, etc). Out of interest, I tried removing some of the other "complicated" merging operations and found that they also worked fine when just regular slices.
Maybe this extra simplification is valid?