overwrite segments for removed code #147
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Not sure how useful this is yet.
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@guybedford @lukastaegert what do you think? I'm not sure I fully understand the implications of this change for downstream users, so I'd refer to others for review. |
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Thanks for much @aleclarson for this PR.
This looks great in principle to me, but the test needs to be updated, and it would ideally come with another test that considers if there are any pathological edge cases of this behaviour - let me know if you can think of any interesting things that may come up here.
| @@ -27,12 +27,20 @@ export default class Mappings { | |||
| let originalCharIndex = chunk.start; | |||
| let first = true; | |||
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| let len = this.rawSegments.length; | |||
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Can we rather call this something more explanatory, perhaps:
let checkDuplicateSegmentIndex = this.rawSegments.length - 1;| while (originalCharIndex < chunk.end) { | ||
| if (this.hires || first || sourcemapLocations[originalCharIndex]) { | ||
| this.rawSegments.push([this.generatedCodeColumn, sourceIndex, loc.line, loc.column]); | ||
| if (len !== 0) { |
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This would then become if (checkDuplpicateSegmentIndex !== -1)
| if (len !== 0) { | ||
| const segment = this.rawSegments[len - 1]; | ||
| if (segment[0] === this.generatedCodeColumn) { | ||
| len -= 1; // overwrite segments for removed code |
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These changes to len can be unnecessary if you just modify the last segment directly:
this.rawSegments[checkDuplicateSegmentIndex] = [...];| len -= 1; // overwrite segments for removed code | ||
| } | ||
| } | ||
| this.rawSegments[len++] = [this.generatedCodeColumn, sourceIndex, loc.line, loc.column]; |
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The default path should be able to then revert to a .push as before.
| } | ||
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| if (original[originalCharIndex] === '\n') { | ||
| len = 0; |
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And this becomes checkDuplicateSegmentIndex = -1 making it clearer this is a switch on the loop.
Removed ranges create two source map segments that refer to the same generated column. I consider this bloat if there isn't a good reason behind it. Generally, there shouldn't be segments for removed code (not including the segment for the characters after, whose source column is the removed range's end column).
What's your take on this, @mourner and/or @Rich-Harris?
Figured I should get feedback before writing any tests.