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[PERF] BundleWriter: Improve performance #534

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merged 5 commits into from
Oct 22, 2020
Merged

[PERF] BundleWriter: Improve performance #534

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713acb3
[FIX] BundleWriter: Improve performance
matz3 Oct 21, 2020
b6e960a
Fix tests
matz3 Oct 21, 2020
762c67c
Fix regexp
matz3 Oct 21, 2020
0e91258
Add tests / fix endsWithNewLine detection
matz3 Oct 22, 2020
cc09738
Update SPACES_OR_TABS_ONLY regexp
matz3 Oct 22, 2020
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15 changes: 11 additions & 4 deletions lib/lbt/bundle/BundleWriter.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@


const NL = "\n";
const ENDS_WITH_NEW_LINE = /(^|\r\n|\r|\n)[ \t]*$/;
const ENDS_WITH_NEW_LINE = /(\r\n|\r|\n)[ \t]*$/;

/**
* A filtering writer that can count written chars and provides some convenience
Expand All @@ -20,11 +20,17 @@ class BundleWriter {
this.segments = [];
this.currentSegment = null;
this.currentSourceIndex = 0;
this.endsWithNewLine = true; // Initially we don't need a new line
}

write(...str) {
let writeBuf = "";
for ( let i = 0; i < str.length; i++ ) {
this.buf += str[i];
writeBuf += str[i];
}
if ( writeBuf.length >= 1 ) {
this.buf += writeBuf;
this.endsWithNewLine = ENDS_WITH_NEW_LINE.test(writeBuf);
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This can give wrong results when write is called with blanks or tabs only. In that case, the old endsWithNewLine flag must be taken into account as well.

Correct would be something like

  ENDS_WITH_NEW_LINE.test(writeBuf) || (this.endsWithNewLine && !writeBuf.trim())

Instead of the trim(), one could use another RegExp /^[ \t]*$/

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Sounds right 👍🏻
As there were no dedicated unit tests, I've added one to cover the whole class.

}
}

Expand All @@ -33,12 +39,13 @@ class BundleWriter {
this.buf += str[i];
}
this.buf += NL;
this.endsWithNewLine = true;
}

ensureNewLine() {
// TODO this regexp might be quite expensive (use of $ anchor on long strings)
if ( !ENDS_WITH_NEW_LINE.test(this.buf) ) {
if ( !this.endsWithNewLine ) {
this.buf += NL;
this.endsWithNewLine = true;
}
}

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